WO2020111404A1 - Method for manufacturing lithium-transition metal oxide using prussian blue analogue, lithium-transition metal oxide, and lithium secondary battery - Google Patents

Method for manufacturing lithium-transition metal oxide using prussian blue analogue, lithium-transition metal oxide, and lithium secondary battery Download PDF

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WO2020111404A1
WO2020111404A1 PCT/KR2019/004680 KR2019004680W WO2020111404A1 WO 2020111404 A1 WO2020111404 A1 WO 2020111404A1 KR 2019004680 W KR2019004680 W KR 2019004680W WO 2020111404 A1 WO2020111404 A1 WO 2020111404A1
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transition metal
lithium
metal oxide
formula
pba
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French (fr)
Korean (ko)
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송태섭
박현중
김정헌
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한양대학교 산학협력단
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G53/00—Compounds of nickel
    • C01G53/40—Nickelates
    • C01G53/42—Nickelates containing alkali metals, e.g. LiNiO2
    • C01G53/44—Nickelates containing alkali metals, e.g. LiNiO2 containing manganese
    • C01G53/50—Nickelates containing alkali metals, e.g. LiNiO2 containing manganese of the type [MnO2]n-, e.g. Li(NixMn1-x)O2, Li(MyNixMn1-x-y)O2
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G53/00—Compounds of nickel
    • 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
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • 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
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • 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
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/60—Compounds characterised by their crystallite size
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/30—Particle morphology extending in three dimensions
    • C01P2004/38—Particle morphology extending in three dimensions cube-like
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/40—Electric properties
    • 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 secondary battery, and more particularly, to a lithium secondary battery.
  • Secondary battery refers to a battery that can be used repeatedly because it can be charged as well as discharge.
  • the representative lithium secondary battery among the secondary batteries is the lithium ions contained in the positive electrode active material is transferred to the negative electrode through the electrolyte and then inserted into the layered structure of the negative electrode active material (charging), and then the lithium ions that have been inserted into the layered structure of the negative electrode active material again It works through the principle of returning to the anode (discharging).
  • These lithium secondary batteries are currently commercialized and used as small power sources such as mobile phones and notebook computers, and are expected to be used as large power sources such as hybrid vehicles, and the demand is expected to increase.
  • a typical lithium transition metal oxide mainly used as a positive electrode active material in a lithium secondary battery has a disadvantage of high rate characteristics, that is, low output characteristics.
  • the problem to be solved by the present invention is to provide a new method for manufacturing a lithium transition metal oxide used as a positive electrode active material for a lithium secondary battery, and to provide a lithium transition metal oxide capable of improving the high rate characteristics of a lithium secondary battery. .
  • an aspect of the present invention provides a method for manufacturing a lithium-transition metal oxide.
  • the method for producing a lithium-transition metal oxide includes forming prussian blue analogue (hereinafter referred to as PBA) particles represented by Chemical Formula 1 below.
  • PBA particles are dispersed in an aqueous solution in which lithium salt is dissolved, filtered and dried to coat the PBA particles with lithium salt.
  • the lithium salt-coated PBA particles are oxidized or pyrolyzed in an air atmosphere to change CN bridges (-CN-) in the PBA to oxygen bridges (-O-).
  • the result of the oxidation step is calcined to obtain a lithium-transition metal oxide.
  • M 1 and M 2 are transition metals having a divalent oxidation number and are Ni, Mn, Co, Fe, Ti, V, or Cr regardless of each other, and M 3 is a transition metal having a trivalent oxidation number.
  • Ni, Mn, Co, Fe, Ti, V, or Cr, c is 1 to 5, and a and b have positive values to make the compound of Formula 1 electrically neutral.
  • the aqueous solution of the salt of the first transition metal and the salt of the second transition metal may further include sodium citrate.
  • the lithium salt may be LiOH.
  • the PBA particles coated with the lithium salt are dispersed in an aqueous transition metal precursor solution, filtered and dried to form PBA particles coated with a lithium salt and a transition metal precursor in turn.
  • the transition metal precursor may include precursors of transition metals constituting the PBA.
  • the pyrolysis temperature may be 400 to 500 degrees.
  • a phase transition occurs in the calcination step, and the calcination step includes a primary calcination step and a secondary calcination step, and may include a cooling step between the primary calcination step and the secondary calcination step.
  • the primary calcination may be performed at 800 to 900 degrees, and the secondary calcination may be performed at 750 to 850 degrees.
  • the lithium-transition metal oxide may be a lithium-transition metal oxide represented by the following Chemical Formula 2.
  • the ratio of x:y:z may be the same as the ratio of a:b:c in Formula 1.
  • the lithium-transition metal oxide has a regular shape of a particle and is represented by the following Chemical Formula 2.
  • the lithium transition metal oxide exhibits a hexagonal layered structure in which the transition metal oxide layer and the lithium layer are arranged repeatedly, and in the crystal of the lithium transition metal oxide, the c-axis length is larger than the a-axis length.
  • the c-axis length/a-axis length represents a value of 1.4 to 1.5.
  • M 1 may be Ni
  • M 2 may be Mn
  • M 3 may be Co
  • the lithium secondary battery may include a positive electrode including a positive electrode active material, which is a lithium-transition metal oxide defined by Chemical Formula 2; A negative electrode containing a negative electrode active material; And an electrolyte disposed between the positive electrode and the negative electrode.
  • a positive electrode active material which is a lithium-transition metal oxide defined by Chemical Formula 2
  • a negative electrode containing a negative electrode active material and an electrolyte disposed between the positive electrode and the negative electrode.
  • the lithium-transition metal oxide produced thereby has a stable structure during charging/discharging, thereby exhibiting excellent battery performance, particularly high rate characteristics. You can...
  • FIG. 1 is a schematic diagram schematically showing an active material manufacturing method according to an embodiment of the present invention.
  • Figure 8 is a graph showing the discharge capacity change according to the rate of crate (c-rate) of the half-cell according to Comparative Example 1, half-cell comparison Example 1, and half-cell comparison.
  • FIG. 1 is a schematic diagram schematically showing an active material manufacturing method according to an embodiment of the present invention.
  • metal hexacyanometallates represented by Chemical Formula 1 may be formed.
  • the metal hexacyanometallate may also be referred to as a prussian blue analogue (hereinafter referred to as PBA).
  • PBA prussian blue analogue
  • the Prussian Blue analog is a type of metal organic structure, and the iron ion is replaced with another metal ion based on the structure (Prussian Blue) formed through chemical bonding between iron and cyano (CN) groups. It means the group of materials.
  • M 1 and M 2 are transition metals having a divalent oxidation number, and may be Ni, Mn, Co, Fe, Ti, V, or Cr regardless of each other, and M 3 is a transition having a trivalent oxidation number
  • the metal may be Ni, Mn, Co, Fe, Ti, V, or Cr.
  • M 1 may be Ni
  • M 2 may be Mn
  • M 3 may be Co
  • c may be 1 to 5.
  • a and b may have a positive value to make the compound of Formula 1 electrically neutral.
  • the PBA may be Ni 2 Mn[Co(CN) 6 ] 2 or NiMn 2 [Co(CN) 6 ] 2 .
  • the PBA may have a particle shape, and the shape of the particle may be, for example, a cube surrounded by a rectangle, and a cube.
  • the cube may mean that all sides have the same length within an error range of 5%, and all angles are equal within an error range of 5%.
  • the PBA represented by Chemical Formula 1 may be formed using a co-precipitation method.
  • an aqueous transition metal salt solution is mixed with an aqueous solution of K 3 M 3 (CN) 6 (M 3 is as defined in Chemical Formula 1), and then the mixed solution is aged to form a precipitate, and the precipitate is filtered to obtain
  • the PBA represented by Chemical Formula 1 can be formed.
  • the transition metal salt may include a salt of a first transition metal (M 1 defined in Formula 1) and a salt of a second transition metal (M 2 defined in Formula 1).
  • the first transition metal and the second transition metal may be the same or different transition metals.
  • the salt of the first transition metal and the salt of the second transition metal may be nitrate or sulfate regardless of each other.
  • the aqueous transition metal salt solution may further include a shape control agent.
  • the shape control agent serves to help form a Prussian blue crystal structure, and may be PVP (Polyvinylpyrrolidone), PDDA (Poly(diallyldimethylammonium chloride)), CTAB (Cetyl trimethylammonium bromide), or sodium citrate. Can be.
  • the temperature for aging the mixed solution may be room temperature, and the aging time may be 3 to 5 weeks.
  • the PBA particles can be dispersed in an aqueous solution in which the lithium salt is dissolved, filtered and dried to coat the PBA particles with a lithium salt. At this time, the surface and internal pores of the PBA particles may be coated with a lithium salt.
  • the lithium salt may be LiOH or LiCO 3 as an example.
  • the PBA particles coated with lithium salt are dispersed in an aqueous transition metal precursor solution, filtered and dried to coat the PBA particles coated with lithium salt (PBA@alkaline salt) again with a transition metal precursor.
  • PBA@lithium salt@transition metal precursor PBA@lithium salt@transition metal precursor
  • the surface and internal pores of the PBA particles may be coated in turn with a lithium salt and a transition metal precursor.
  • the transition metal precursor coating step may be omitted in some cases.
  • the transition metal precursor may include precursors of transition metals constituting the PBA.
  • the transition metal precursor when the PBA contains nickel, manganese, and cobalt, is a nickel precursor specifically nickel nitrate or nickel sulfate, a manganese precursor specifically manganese nitrate or manganese sulfate, and a cobalt precursor specifically cobalt nitrate Or cobalt sulfate.
  • the thermal decomposition temperature may be about 400 to 500 degrees, and the thermal decomposition time may be about 2 to 4 hours.
  • the CN bridges between transition metals are oxidized and converted to oxygen bridges, so that the distance between the transition metals becomes close and collapse of the particle shape may occur.
  • the aging time is set to 3 weeks to 5 weeks as an example, as described above, it is possible to sufficiently reduce the occurrence of crystal defects in the PBA particles, in the thermal decomposition process.
  • the collapse of the particle shape can be greatly reduced or the collapse of the particle shape can be prevented.
  • the temperature rise rate during thermal decomposition proceeds relatively slowly to 0.5 to 1.5°C/min to maintain the shape of the particles.
  • M 1 , M 2 and M 3 may be Ni, Mn, Co, Fe, Ti, V, or Cr, regardless of each other.
  • M 1, M 2 and M 3 are M 1, M 2, and are the same oxidation state transition metal, respectively, and M 3 in the formula (1) of the general formula (2) may or may not be equal.
  • M 1 may be Ni
  • M 2 may be Mn
  • M 3 may be Co.
  • the ratio of x:y:z may be the same as the ratio of a:b:c in Chemical Formula 1 above. However, it is not limited thereto.
  • the lithium transition metal oxide represented by Chemical Formula 2 may exhibit a hexagonal layered structure in which the transition metal oxide layer and the lithium layer are repeatedly arranged, and O3 among the layered structures. Structure.
  • the c-axis length/a-axis length that is, I (003) /I (104) in the XRD graph may exhibit a value of more than 1, further 1.2 or more, further 1.4 or more, and 1.5 or less.
  • cation mixing which is a phenomenon in which other transition metal cations (especially nickel ions) are inserted instead of lithium ions, can be suppressed.
  • the shape of the particles of the lithium transition metal oxide represented by Chemical Formula 2 may be, for example, a cube surrounded by a rectangle, and a cube.
  • the surface area may be larger at the same volume than when the particle shape is spherical. This can be seen as an increase in capacity due to an increase in the reaction area.
  • the cube may mean that all sides have the same length within an error range of 5%, and all angles are equal within an error range of 5%. Meanwhile, the length of each side of the cube may be about 50 to 150 nm.
  • the calcination may include a primary calcination step and a secondary calcination step, and may include cooling to room temperature before starting the secondary calcination after terminating the primary calcination.
  • the calcination can be performed in an air atmosphere.
  • the temperature for the primary calcination may be 800 to 900 degrees, and the treatment time may be about 3 to 6 hours.
  • the obtained resultant lithium-transition metal oxide powder may be ground at room temperature and then subjected to the second calcination.
  • the temperature for the second calcination can be 750 to 850 degrees, and the treatment time can be about 4 to 5 hours.
  • the temperature increase rate can be relatively slow to 4 to 6°C/min to maintain the shape of the particles.
  • the transition metal precursor coated on the particles may maintain the shape of the particles stably despite the phase transition during calcination in the thermal decomposition process.
  • the active material which is a lithium-transition metal oxide, is used as a positive electrode active material for a lithium secondary battery, which will be described later, so that the particle structure can be stably maintained even when the lithium secondary battery is driven, so that efficiency and high rate characteristics can be excellent.
  • the lithium secondary battery according to an embodiment of the present invention may include a positive electrode containing the active material described above as a positive electrode active material, a negative electrode containing a negative electrode active material capable of deintercalating lithium ions, and an electrolyte positioned therebetween. .
  • a positive electrode material may be obtained by mixing the positive electrode active material, a conductive material, and a binder.
  • the conductive material may be natural graphite, artificial graphite, coke, carbon black, carbon nanotubes, graphene, and other carbon materials.
  • Binders include thermoplastic resins such as polyvinylidene fluoride, polytetrafluoroethylene, ethylene tetrafluoride, vinylidene fluoride copolymers, fluorine resins such as propylene hexafluoride, and/or polyolefin resins such as polyethylene and polypropylene. It can contain.
  • the positive electrode material may be coated on the positive electrode current collector to form the positive electrode.
  • the positive electrode current collector may be a conductor such as Al, Ni, and stainless steel.
  • Applying the positive electrode material on the positive electrode current collector may be a method of forming a paste using pressure molding or an organic solvent, and then applying the paste onto the current collector and pressing to fix it.
  • Organic solvents include amines such as N,N-dimethylaminopropylamine and diethyltriamine; Ether systems such as ethylene oxide and tetrahydrofuran; Ketone systems such as methyl ethyl ketone; Ester systems such as methyl acetate; Aprotic polar solvents such as dimethylacetamide and N-methyl-2-pyrrolidone.
  • Applying the paste on the positive electrode current collector can be performed using, for example, a gravure coating method, a slit die coating method, a knife coating method, or a spray coating method.
  • the negative electrode active material is a metal, a metal alloy, a metal oxide, a metal fluoride, a metal sulfide, and natural graphite, artificial graphite, coke, carbon black, carbon nanotube, graphene, which can deintercalate or convert lithium ions. It can also be formed using a carbon material such as fin.
  • a negative electrode material can be obtained by mixing a negative electrode active material, a conductive material, and a binder.
  • the conductive material may be natural graphite, artificial graphite, coke, carbon black, carbon nanotubes, graphene, and other carbon materials.
  • Binders include thermoplastic resins such as polyvinylidene fluoride, polytetrafluoroethylene, ethylene tetrafluoride, vinylidene fluoride copolymers, fluorine resins such as propylene hexafluoride, and/or polyolefin resins such as polyethylene and polypropylene. It can contain.
  • the negative electrode material may be coated on the negative electrode current collector to form a negative electrode.
  • the negative electrode current collector may be a conductor such as Al, Ni, and stainless steel.
  • Applying the negative electrode material on the negative electrode current collector may be a method of forming a paste using pressure molding or an organic solvent, and then applying the paste onto the current collector and pressing it to fix it.
  • Organic solvents include amines such as N,N-dimethylaminopropylamine and diethyltriamine; Ether systems such as ethylene oxide and tetrahydrofuran; Ketone systems such as methyl ethyl ketone; Ester systems such as methyl acetate; Aprotic polar solvents such as dimethylacetamide and N-methyl-2-pyrrolidone.
  • Applying the paste on the negative electrode current collector may be performed using, for example, a gravure coating method, a slit die coating method, a knife coating method, or a spray coating method.
  • the electrolyte may be a liquid electrolyte containing a lithium salt and a solvent dissolving it.
  • the solvent may be an organic solvent.
  • an organic solvent for example, propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, isopropyl methyl carbonate , Carbonates such as vinylene carbonate, 4-trifluoromethyl-1,3-dioxolan-2-one and 1,2-di(methoxycarbonyloxy)ethane; 1,2-dimethoxyethane, 1,3-dimethoxypropane, pentafluoropropylmethyl ether, 2,2,3,3-tetrafluoropropyldifluoromethyl ether, tetrahydrofuran, 2-methyltetrahydro Ethers such as furan; Esters such as methyl formate, methyl acetate, and ⁇ -butyrolactone; Nitriles such as acetonitrile and butyronitrile; Amides such as N,N-dimethylformamide and N,N-dimethylacet
  • the electrolyte is not limited thereto, and the liquid electrolyte may be a polymer solid electrolyte or a ceramic solid electrolyte impregnated into the polymer.
  • the polymer may be a polymer compound containing at least one of a polyethylene oxide-based polymer compound, a polyorganosiloxane chain, or a polyoxyalkylene chain.
  • the ceramic type solid electrolyte may also use inorganic ceramics such as sulfide, oxide, and phosphate of the metal.
  • the solid electrolyte may serve as a separator to be described later, and in that case, a separator may not be required.
  • a separator may be disposed between the anode and the cathode.
  • the separator may be a material having a form of a porous film made of a material such as polyethylene, polypropylene, polyolefin resin, fluorine resin, or nitrogen-containing aromatic polymer, nonwoven fabric, woven fabric, or the like.
  • the thickness of the separator is preferably as thin as possible, as long as the mechanical strength is maintained, in that the bulk energy density of the battery increases and the internal resistance decreases.
  • a positive electrode, a separator, and a negative electrode may be stacked in order to form an electrode group, and then, if necessary, the electrode group may be rolled and stored in a battery can, and a lithium secondary battery may be manufactured by impregnating the electrode group with an electrolyte solution.
  • a positive electrode, a solid electrolyte, and a negative electrode may be stacked to form an electrode group, and then, if necessary, the electrode group may be rolled and stored in a battery can to manufacture a metal secondary battery.
  • PBA@LiOH@NCM powder in a crucible was treated in a furnace in an air atmosphere at 450°C for 1 hour/min for 3 hours to oxidize CN ligands in the PBA, and then for 5 hours at 5°C/min up to 850°C gave. Thereafter, after pulverizing the powder, further heat treatment was performed at 5°C/min for 5 hours to 800°C to obtain a Li[Ni 0.4 Co 0.4 Mn 0.2 ]O 2 powder.
  • An active material (Li-NCM oxide) was prepared in the same manner as the active material preparation example, except that the transition metal precursor coating step was omitted.
  • FIG. 2 shows SEM (scanning electron microscope) photographs of the active material according to Preparation Example 1
  • FIG. 3 shows SEM photographs of the active material according to Preparation Example 2.
  • FIG. 4 shows an SEM photograph of an active material according to Comparative Example 1 of the active material
  • FIG. 5 shows an SEM photograph of an active material according to Comparative Example 2 of the active material. It can be seen that many defects occurred in the active material after firing. This is because the aging time in the PBA powder manufacturing step, that is, the synthesis time according to the co-precipitation method is short, so many crystal defects in the PBA occur, and when the CN ligands are oxidized in the firing step, the CN bridges are converted into oxygen bridges. The gap was narrowed and it was estimated that the structure was difficult to maintain due to the Ostwald ripening phenomenon.
  • the active material according to the comparative example 1 of the active material maintains the particle shape of the cube even after firing.
  • the aging time was greatly increased to minimize the formation of crystal defects in the PBA, so the CN bridges due to oxidation of the CN ligands appearing in the firing process are converted into oxygen bridges, and thus the interval between the metals is It was presumed that the particle structure was maintained despite the shrinking and Ostwald life.
  • the particle size is also larger than the active material particles according to Comparative Example 2, which was judged because the crystal growth was sufficiently achieved.
  • the active material according to Comparative Example 1 and Active Material Comparative Example 2 was subjected to heat treatment at 450° C. for 3 hours (first), heat treatment at 800° C. for 3 hours (second), and heat treatment at 800° C. for 5 hours (third).
  • first heat treatment
  • second heat treatment
  • third heat treatment
  • the second heat treatment is heat treated at 850° C. for 5 hours as in the case of the active material preparation example 1
  • the aging time is short as 2 weeks as in the active material comparative example 1
  • the collapse of the structure occurs more severely or it is aged as in the active material comparative example 2 Even when the time was increased to 4 weeks, structural collapse was observed.
  • the active material according to the active material preparation example 1 relatively maintains the shape of the particles, that is, the shape of the cube, even after the heat treatment step.
  • the length of one side of the particle is about 1 um, and irregular hexahedral nanoparticles on the surface of the particle are identified.
  • the active material according to Preparation Example 1 of the active material is nano-sized. It can be seen that the primary particles are secondary particles generated by aggregation.
  • the active material according to the active material preparation example 2 has a somewhat collapsed particle shape compared to the active material production example 1 (FIG. 2 ), which is a heat treatment process (450° C.) without adding a transition metal precursor in the manufacturing process. It was estimated that 3 hours heat treatment (first), 850°C 5 hours heat treatment (second), and 800°C 5 hours heat treatment (third) were performed. From these results, it can be seen that when the transition metal precursor is added in the active material manufacturing process and then the heat treatment process is performed, the collapse of the particle structure can be suppressed.
  • the XRD pattern of the active material obtained in Preparation Example 1 shows (003) peak and (104) peak, and (003) peak intensity (I 003 ) is (104) peak intensity (I 104 ) It can be seen that it shows a larger value than.
  • the ratio of I 003 /I 104 is greater than 1, furthermore 1.2 or more, further 1.4 or more, and 1.5 or less Specifically, it represents a value of 1.47.
  • the ratio of I 003 /I 104 is an index for determining cation mixing, which is a phenomenon in which other transition metal cations (especially nickel ions) are inserted instead of lithium ions at the lithium ion site, and the ratio of I 003 /I 104 It is known that when it is more than 1, cation mixing becomes low, and further, when it is 1.2 or more, cation mixing becomes sufficiently low. Accordingly, it can be seen that the active material according to the active material preparation example 1 sufficiently suppressed the cation mixing phenomenon, and it was estimated that capacity and efficiency could be improved.
  • a semi-prepared paper was manufactured through the same process as the semi-prepared paper manufacturing example, except that the active material prepared in Comparative Example 1 was used as the positive electrode active material instead of the positive electrode active material prepared in Preparation Example 1.
  • a semi-prepared paper was prepared through the same process as the semi-prepared paper manufacturing example, except that the active material prepared in Comparative Example 2 was used as the positive electrode active material instead of the positive electrode active material prepared in Preparation Example 1.
  • FIG. 7 is a graph showing charging and discharging characteristics in the first cycle of the reverse cells according to Comparative Example 1, Semi-Compared Paper Comparative Example 1, and Comparative Paper 2. At this time, the capacity was measured while charging was performed at 0.1C to 4.4V and discharge was performed at 0.1C to 3.0V.
  • a half-sheet according to Preparation Example 1 that is, a half-sheet using the active material according to Preparation Example 1, a half-sheet according to Comparative Examples, and an active material according to Comparative Examples
  • the initial charge capacity and discharge capacity are relatively low compared to the reverse cells using, while the ratio of charge capacity/discharge capacity, that is, cycle efficiency is excellent. This was estimated because the capacity of the active material according to Comparative Examples increased due to the increase in porosity due to the collapse of the particle structure as described above, but the efficiency decreased. It was estimated that the capacity was relatively small, but the efficiency was excellent because it could be kept stable.
  • Figure 8 is a graph showing the discharge capacity change according to the rate of crate (c-rate) of the half-cell according to Comparative Example 1, half-cell comparison Example 1, and half-cell comparison.
  • the 1st to 3rd cycles are 0.1C, 0.2C, and the 4th to 6th cycles at 0.5C, the 7th to 9th cycles at 2C, the 10th to 12th cycles at 4C, and the 13th to 15th cycles again.
  • Charging from 1C to 4.4V and discharging to 3.0V were repeated.
  • the reverse paper according to Preparation Example 1 that is, the reverse material using the active material according to Preparation Example 1
  • the reverse paper according to the comparison examples of the reverse paper that is, the active material according to the comparative examples
  • the active material according to the active material preparation example 1 was estimated to have excellent high rate characteristics because the particle structure can be stably maintained.

Abstract

A method for manufacturing a lithium-transition metal oxide is provided. The method for manufacturing a lithium-transition metal oxide comprises a step of forming Prussian blue analogue (hereinafter, refer to as PBA) particles represented by chemical formula 1 below. The PBA particles are dispersed in an aqueous solution of a lithium salt, filtered, and dried to coat the PBA particles with the lithium salt. The lithium salt-coated PBA particles are pyrolyzed under an air atmosphere to oxidize CN bridges in PBA into oxygen bridges. The resultant product that has undergone the oxidization step is calcined to obtain a lithium-transition metal oxide. [Chemical formula 1] M1 aM2 b[M3(CN)6]c , wherein M1 and M2 are transition metals each having an oxidation number of 2 and being independently Ni, Mn, Co, Fe, Ti, V, or Cr; M3 is a transition metal having an oxidation number of 3 and is Ni, Mn, Co, Fe, Ti, V, or Cr; c is 1 to 5; and a and b have positive values to electrically neutralize the compound of chemical formula 1.

Description

프러시안 블루 아날로그를 사용한 리튬-전이금속 산화물 제조 방법, 리튬-전이금속 산화물, 및 리튬 이차 전지 Method for manufacturing lithium-transition metal oxide using Prussian blue analog, lithium-transition metal oxide, and lithium secondary battery
본 발명은 이차전지에 관한 것으로, 보다 상세하게는 리튬 이차전지에 관한 것이다.The present invention relates to a secondary battery, and more particularly, to a lithium secondary battery.
이차전지는 방전뿐 아니라 충전이 가능하여 반복적으로 사용할 수 있는 전지를 말한다. 이차전지 중 대표적인 리튬 이차전지는 양극활물질에 포함된 리튬이온이 전해질을 거쳐 음극으로 이동한 후 음극활물질의 층상 구조 내로 삽입되며(충전), 이 후 음극활물질의 층상 구조 내로 삽입되었던 리튬 이온이 다시 양극으로 되돌아가는(방전) 원리를 통해 작동한다. 이러한 리튬 이차전지는 현재 상용화되어 휴대전화, 노트북 컴퓨터 등의 소형전원으로 사용되고 있으며, 하이브리드 자동차 등의 대형 전원으로도 사용가능할 것으로 예측되고 있어, 그 수요가 증대될 것으로 예상된다.Secondary battery refers to a battery that can be used repeatedly because it can be charged as well as discharge. The representative lithium secondary battery among the secondary batteries is the lithium ions contained in the positive electrode active material is transferred to the negative electrode through the electrolyte and then inserted into the layered structure of the negative electrode active material (charging), and then the lithium ions that have been inserted into the layered structure of the negative electrode active material again It works through the principle of returning to the anode (discharging). These lithium secondary batteries are currently commercialized and used as small power sources such as mobile phones and notebook computers, and are expected to be used as large power sources such as hybrid vehicles, and the demand is expected to increase.
그러나, 리튬 이차전지에서 양극활물질로 주로 사용되는 일반적인 리튬 전이금속 산화물은 고율특성 즉, 고출력특성이 낮은 단점이 있다.However, a typical lithium transition metal oxide mainly used as a positive electrode active material in a lithium secondary battery has a disadvantage of high rate characteristics, that is, low output characteristics.
본 발명이 해결하고자 하는 과제는, 리튬 이차전지의 양극 활물질로 사용되는 리튬 전이금속 산화물의 새로운 제조방법을 제시하고, 또한 리튬 이차전지의 고율특성을 향상시킬 수 있는 리튬 전이금속 산화물을 제공함에 있다. The problem to be solved by the present invention is to provide a new method for manufacturing a lithium transition metal oxide used as a positive electrode active material for a lithium secondary battery, and to provide a lithium transition metal oxide capable of improving the high rate characteristics of a lithium secondary battery. .
본 발명의 기술적 과제들은 이상에서 언급한 기술적 과제로 제한되지 않으며, 언급되지 않은 또 다른 기술적 과제들은 아래의 기재로부터 당업자에게 명확하게 이해될 수 있을 것이다.The technical problems of the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the following description.
상기 기술적 과제를 이루기 위하여 본 발명의 일 측면은 리튬-전이금속 산화물 제조 방법을 제공한다. 리튬-전이금속 산화물 제조 방법은 하기 화학식 1로 나타낸 프러시안 블루 아날로그(prussian blue analogue; 이하 PBA라고 한다) 입자들을 형성하는 단계를 포함한다. 상기 PBA 입자들을 리튬염이 용해된 수용액 내에 분산시키고 필터링 및 건조하여, 상기 PBA 입자들을 리튬염으로 코팅한다. 상기 리튬염으로 코팅된 PBA 입자들을 공기분위기에서 산화 또는 열분해하여(pyrolysis)하여 PBA 내의 CN 브릿지들(-CN-)을 산소 브릿지들(-O-)로 변화시킨다. 상기 산화 단계를 거친 결과물을 하소하여(calcination) 리튬-전이금속 산화물을 얻는다.In order to achieve the above technical problem, an aspect of the present invention provides a method for manufacturing a lithium-transition metal oxide. The method for producing a lithium-transition metal oxide includes forming prussian blue analogue (hereinafter referred to as PBA) particles represented by Chemical Formula 1 below. The PBA particles are dispersed in an aqueous solution in which lithium salt is dissolved, filtered and dried to coat the PBA particles with lithium salt. The lithium salt-coated PBA particles are oxidized or pyrolyzed in an air atmosphere to change CN bridges (-CN-) in the PBA to oxygen bridges (-O-). The result of the oxidation step is calcined to obtain a lithium-transition metal oxide.
[화학식 1][Formula 1]
M1 aM2 b[M3(CN)6]c M 1 a M 2 b [M 3 (CN) 6 ] c
상기 화학식 1에서, M1 및 M2는 2가의 산화수를 갖는 전이금속으로 서로에 관계없이 Ni, Mn, Co, Fe, Ti, V, 또는 Cr이고, M3는 3가의 산화수를 갖는 전이금속으로 Ni, Mn, Co, Fe, Ti, V, 또는 Cr이고, c은 1 내지 5이고, a와 b는 상기 화학식 1의 화합물을 전기적으로 중성이 되도록 하는 양의 값을 갖는다.In Chemical Formula 1, M 1 and M 2 are transition metals having a divalent oxidation number and are Ni, Mn, Co, Fe, Ti, V, or Cr regardless of each other, and M 3 is a transition metal having a trivalent oxidation number. Ni, Mn, Co, Fe, Ti, V, or Cr, c is 1 to 5, and a and b have positive values to make the compound of Formula 1 electrically neutral.
상기 PBA 입자들은, 제1 전이금속(상기 화학식 1에서 정의된 M1)의 염과 제2 전이금속(상기 화학식 1에서 정의된 M2)의 염의 수용액을 K3M3(CN)6 (M3는 상기 화학식 1에서 정의된 바와 같음)의 수용액과 혼합한 후 혼합용액을 숙성시켜 침전물을 형성하고, 침전물을 필터링하여 얻을 수 있다.The PBA particles, an aqueous solution of a salt of a first transition metal (M 1 defined in Formula 1) and a salt of a second transition metal (M 2 defined in Formula 1) K 3 M 3 (CN) 6 (M 3 is mixed with an aqueous solution as defined in Chemical Formula 1), and then the mixed solution is aged to form a precipitate, and can be obtained by filtering the precipitate.
상기 제1 전이금속의 염과 상기 제2 전이금속의 염의 수용액은 구연산 나트륨(sodium citrate)을 더 포함할 수 있다.The aqueous solution of the salt of the first transition metal and the salt of the second transition metal may further include sodium citrate.
상기 리튬염은 LiOH일 수 있다.The lithium salt may be LiOH.
상기 리튬염으로 코팅된 PBA 입자들을 열분해하기 전에, 상기 리튬염으로 코팅된 PBA 입자들을 전이금속 전구체 수용액 내에 분산시키고 필터링 및 건조하여 리튬염과 전이금속 전구체로 차례로 코팅된 PBA 입자들을 형성하되, 상기 전이금속 전구체는 상기 PBA를 구성하는 전이금속들의 전구체를 포함할 수 있다.Before thermally decomposing the PBA particles coated with the lithium salt, the PBA particles coated with the lithium salt are dispersed in an aqueous transition metal precursor solution, filtered and dried to form PBA particles coated with a lithium salt and a transition metal precursor in turn. The transition metal precursor may include precursors of transition metals constituting the PBA.
상기 열분해 온도는 400도 내지 500도일 수 있다. The pyrolysis temperature may be 400 to 500 degrees.
상기 하소 단계에서 상전이가 발생하고, 상기 하소 단계는 1차 하소 단계와 2차 하소 단계를 포함하고, 상기 1차 하소 단계와 상기 2차 하소 단계 사이에 냉각 단계를 포함할 수 있다.A phase transition occurs in the calcination step, and the calcination step includes a primary calcination step and a secondary calcination step, and may include a cooling step between the primary calcination step and the secondary calcination step.
상기 1차 하소는 800 내지 900도에서 수행하고, 상기 2차 하소는 750 내지 850도에서 수행할 수 있다.The primary calcination may be performed at 800 to 900 degrees, and the secondary calcination may be performed at 750 to 850 degrees.
상기 리튬-전이금속 산화물은 하기 화학식 2로 나타낸 리튬-전이금속 산화물일 수 있다.The lithium-transition metal oxide may be a lithium-transition metal oxide represented by the following Chemical Formula 2.
[화학식 2][Formula 2]
Li[M1 xM2 yM3 z]O2 Li[M 1 x M 2 y M 3 z ]O 2
상기 화학식 2에서 M1, M2 및 M3는 상기 화학식 1의 M1, M2 및 M3와 각각 동일한 전이금속이되 산화수는 동일하거나 동일하지 않고, x, y, z는 x+y+z=1을 만족하는 조건에서 0.1 내지 0.8의 값을 갖는다.In Formula 2 M 1, M 2 and M 3 are not the same, M 1, M 2, and are oxidation number is the same transition metal, respectively, and M 3 in the formula (1) or the same, x, y, z is x + y + It has a value of 0.1 to 0.8 in a condition that satisfies z=1.
상기 화학식 2에서 x:y:z의 비는 상기 화학식 1에서의 a:b:c의 비와 같을 수 있다.In Formula 2, the ratio of x:y:z may be the same as the ratio of a:b:c in Formula 1.
상기 기술적 과제를 이루기 위하여 본 발명의 다른 측면은 리튬-전이금속 산화물을 제공한다. 상기 리튬-전이금속 산화물은 입자의 형상이 정육면체이고 하기 화학식 2로 나타내어진다.To achieve the above technical problem, another aspect of the present invention provides a lithium-transition metal oxide. The lithium-transition metal oxide has a regular shape of a particle and is represented by the following Chemical Formula 2.
[화학식 2][Formula 2]
Li[M1 xM2 yM3 z]O2 Li[M 1 x M 2 y M 3 z ]O 2
상기 화학식 2에서 M1, M2 및 M3는 서로에 관계없이 Ni, Mn, Co, Fe, Ti, V, 또는 Cr이고, x, y, z는 x+y+z=1을 만족하는 조건에서 0.1 내지 0.8의 값을 갖는다.In Formula 2, M 1 , M 2 and M 3 are Ni, Mn, Co, Fe, Ti, V, or Cr regardless of each other, and x, y, and z satisfy x+y+z=1 It has a value of 0.1 to 0.8.
상기 리튬 전이금속 산화물은 전이금속 산화물층과 리튬층이 반복되어 배열된 헥사고날 층상 구조(hexagonal layered structure)를 나타내고, 상기 리튬 전이금속 산화물의 결정에서 c축 길이는 a축 길이에 비해 크다. 일 예로서, 상기 리튬 전이금속 산화물의 결정에서 c축 길이/a축 길이는 1.4 내지 1.5의 값을 나타낸다.The lithium transition metal oxide exhibits a hexagonal layered structure in which the transition metal oxide layer and the lithium layer are arranged repeatedly, and in the crystal of the lithium transition metal oxide, the c-axis length is larger than the a-axis length. For example, in the crystal of the lithium transition metal oxide, the c-axis length/a-axis length represents a value of 1.4 to 1.5.
상기 화학식 2에서 M1은 Ni, M2는 Mn, 그리고 M3는 Co일 수 있다.In Formula 2, M 1 may be Ni, M 2 may be Mn, and M 3 may be Co.
상기 기술적 과제를 이루기 위하여 본 발명의 또 다른 측면은 리튬 이차 전지를 제공한다. 상기 리튬 이차 전지는 상기 화학식 2로 정의된 리튬-전이금속 산화물인 양극활물질을 포함하는 양극; 음극활물질을 함유하는 음극; 및 상기 양극과 상기 음극 사이에 배치된 전해질을 포함한다.In order to achieve the above technical problem, another aspect of the present invention provides a lithium secondary battery. The lithium secondary battery may include a positive electrode including a positive electrode active material, which is a lithium-transition metal oxide defined by Chemical Formula 2; A negative electrode containing a negative electrode active material; And an electrolyte disposed between the positive electrode and the negative electrode.
상술한 바와 같이 본 발명에 따르면, 리튬-전이금속 산화물을 제조하는 새로은 방법을 제시하고 이에 의해 제조된 리튬-전이금속 산화물은 충/방전 과정에서 구조가 안정화되어 우수한 전지 성능, 특히 고율 특성을 나타낼 수 있다..As described above, according to the present invention, a new method for producing a lithium-transition metal oxide is proposed, and the lithium-transition metal oxide produced thereby has a stable structure during charging/discharging, thereby exhibiting excellent battery performance, particularly high rate characteristics. You can...
그러나, 본 발명의 효과들은 이상에서 언급한 효과로 제한되지 않으며, 언급되지 않은 또 다른 효과들은 아래의 기재로부터 당업자에게 명확하게 이해될 수 있을 것이다.However, the effects of the present invention are not limited to the above-mentioned effects, and other effects not mentioned will be clearly understood by those skilled in the art from the following description.
도 1은 본 발명의 일 실시예에 따른 활물질 제조방법을 개략적으로 나타낸 개략도이다.1 is a schematic diagram schematically showing an active material manufacturing method according to an embodiment of the present invention.
도 2는 활물질 제조예 1에 따른 활물질을 촬영한 SEM(scanning electron microscope) 사진들을 나타낸다.2 shows SEM (scanning electron microscope) photographs of the active material according to Preparation Example 1;
도 3은 활물질 제조예 2에 따른 활물질을 촬영한 SEM 사진들을 나타낸다.3 shows SEM photographs of the active material according to the active material preparation example 2.
도 4는 활물질 비교예 1에 따른 활물질을 촬영한 SEM 사진을 나타낸다.4 shows an SEM photograph of an active material according to Comparative Example 1 of an active material.
도 5는 활물질 비교예 2에 따른 활물질을 촬영한 SEM 사진을 나타낸다.5 shows an SEM photograph of an active material according to Comparative Example 2 of the active material.
도 6은 활물질 제조예 1에서 얻어진 활물질에 대한 XRD 패턴을 나타낸다.6 shows an XRD pattern for the active material obtained in Preparation Example 1 active material.
도 7은 반전지 제조예 1, 반전지 비교예 1, 및 반전지 비교에 2에 따른 반전지들의 첫 번째 사이클에서의 충방전 특성을 나타낸 그래프이다.7 is a graph showing charging and discharging characteristics in the first cycle of the reverse cells according to Comparative Example 1, Semi-Compared Paper Comparative Example 1, and Comparative Paper 2.
도 8은 반전지 제조예 1, 반전지 비교예 1, 및 반전지 비교에 2에 따른 반전지들의 율속(c-rate)에 따른 방전용량 변화를 나타낸 그래프이다.Figure 8 is a graph showing the discharge capacity change according to the rate of crate (c-rate) of the half-cell according to Comparative Example 1, half-cell comparison Example 1, and half-cell comparison.
이하, 본 발명을 보다 구체적으로 설명하기 위하여 본 발명에 따른 바람직한 실시예를 첨부된 도면을 참조하여 보다 상세하게 설명한다. 그러나, 본 발명은 여기서 설명되어지는 실시예에 한정되지 않고 다른 형태로 구체화될 수도 있다. Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the accompanying drawings in order to describe the present invention in more detail. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms.
이차 전지용 활물질Active material for secondary batteries
도 1은 본 발명의 일 실시예에 따른 활물질 제조방법을 개략적으로 나타낸 개략도이다.1 is a schematic diagram schematically showing an active material manufacturing method according to an embodiment of the present invention.
도 1을 참조하면, 먼저, 하기 화학식 1로 나타낸 메탈 헥사시아노메탈레이트(metal hexacyanometallates)를 형성할 수 있다. 메탈 헥사시아노메탈레이트는 프러시안 블루 아날로그(prussian blue analogue; 이하 PBA라고 한다)로 명명될 수도 있다. 상기 프러시안 블루 아날로그는 금속유기구조체의 한 종류로써 철과 시아노(cyano, CN)기의 화학결합을 통해 형성된 구조(프러시안 블루)를 모체로 하여 철 이온이 다른 금속 이온으로 대체되어 있는 파생 소재군을 의미한다.Referring to FIG. 1, first, metal hexacyanometallates represented by Chemical Formula 1 may be formed. The metal hexacyanometallate may also be referred to as a prussian blue analogue (hereinafter referred to as PBA). The Prussian Blue analog is a type of metal organic structure, and the iron ion is replaced with another metal ion based on the structure (Prussian Blue) formed through chemical bonding between iron and cyano (CN) groups. It means the group of materials.
[화학식 1][Formula 1]
M1 aM2 b[M3(CN)6]c M 1 a M 2 b [M 3 (CN) 6 ] c
상기 화학식 1에서, M1 및 M2는 2가의 산화수를 갖는 전이금속으로 서로에 관계없이 Ni, Mn, Co, Fe, Ti, V, 또는 Cr일 수 있고, M3는 3가의 산화수를 갖는 전이금속으로 Ni, Mn, Co, Fe, Ti, V, 또는 Cr일 수 있다. 일 예로서, M1은 Ni일 수 있고, M2는 Mn일 수 있고, M3는 Co일 수 있다. c은 1 내지 5 일 수 있다. 그러a와 b는 상기 화학식 1의 화합물을 전기적으로 중성이 되도록 하는 양의 값을 가질 수 있다.In Formula 1, M 1 and M 2 are transition metals having a divalent oxidation number, and may be Ni, Mn, Co, Fe, Ti, V, or Cr regardless of each other, and M 3 is a transition having a trivalent oxidation number The metal may be Ni, Mn, Co, Fe, Ti, V, or Cr. As an example, M 1 may be Ni, M 2 may be Mn, and M 3 may be Co. c may be 1 to 5. However, a and b may have a positive value to make the compound of Formula 1 electrically neutral.
상기 PBA는 일 예로서, Ni2Mn[Co(CN)6]2 또는 NiMn2[Co(CN)6]2일 수 있다.As an example, the PBA may be Ni 2 Mn[Co(CN) 6 ] 2 or NiMn 2 [Co(CN) 6 ] 2 .
상기 PBA는 입자(particle)의 형상을 가질 수 있고, 이 때 입자의 형상은 사각형으로 둘러싸인 육면체 일 예로서, 정육면체일 수 있다. 이 때, 정육면체는 모든 변의 길이가 5%의 오차 범위 내에서 동일하고, 모든 각이 5%의 오차 범위 내에서 동일한 것을 의미할 수 있다.The PBA may have a particle shape, and the shape of the particle may be, for example, a cube surrounded by a rectangle, and a cube. At this time, the cube may mean that all sides have the same length within an error range of 5%, and all angles are equal within an error range of 5%.
상기 화학식 1로 나타낸 PBA는 공침법을 사용하여 형성할 수 있다.The PBA represented by Chemical Formula 1 may be formed using a co-precipitation method.
일 예로서, 전이금속염 수용액을 K3M3(CN)6 (M3는 상기 화학식 1에서 정의된 바와 같음)의 수용액과 혼합한 후 혼합용액을 숙성시켜 침전물을 형성하고, 침전물을 필터링하여 상기 화학식 1로 나타낸 PBA를 형성할 수 있다. 상기 전이금속염은 제1 전이금속(상기 화학식 1에서 정의된 M1)의 염과 제2 전이금속(상기 화학식 1에서 정의된 M2)의 염을 포함할 수 있다. 이 때, 상기 제1 전이금속과 상기 제2 전이금속은 같거나 서로 다른 전이금속일 수 있다. 상기 제1 전이금속의 염과 제2 전이금속의 염은 서로에 관계없이 질산염 또는 황산염일 수 있다. 상기 전이금속염 수용액은 형상조절제를 더 포함할 수 있다. 상기 형상조절제는 프러시안 블루 결정구조를 형성할 수 있게 도와주는 역할을 하는 것으로, PVP (Polyvinylpyrrolidone), PDDA (Poly(diallyldimethylammonium chloride)), CTAB (Cetyl trimethylammonium bromide), 또는 구연산 나트륨(sodium citrate)일 수 있다. 상기 혼합용액을 숙성시키는 온도는 상온일 수 있고, 또한 숙성시간은 3주 내지 5주일 수 있다. As an example, an aqueous transition metal salt solution is mixed with an aqueous solution of K 3 M 3 (CN) 6 (M 3 is as defined in Chemical Formula 1), and then the mixed solution is aged to form a precipitate, and the precipitate is filtered to obtain The PBA represented by Chemical Formula 1 can be formed. The transition metal salt may include a salt of a first transition metal (M 1 defined in Formula 1) and a salt of a second transition metal (M 2 defined in Formula 1). In this case, the first transition metal and the second transition metal may be the same or different transition metals. The salt of the first transition metal and the salt of the second transition metal may be nitrate or sulfate regardless of each other. The aqueous transition metal salt solution may further include a shape control agent. The shape control agent serves to help form a Prussian blue crystal structure, and may be PVP (Polyvinylpyrrolidone), PDDA (Poly(diallyldimethylammonium chloride)), CTAB (Cetyl trimethylammonium bromide), or sodium citrate. Can be. The temperature for aging the mixed solution may be room temperature, and the aging time may be 3 to 5 weeks.
상기 PBA 입자들을 리튬염이 용해된 수용액 내에 분산시키고 필터링 및 건조하여, 상기 PBA 입자들을 리튬염으로 코팅할 수 있다. 이 때, 상기 PBA 입자의 표면 및 내부 기공은 리튬염으로 코팅될 수 있다. 상기 리튬염은 일 예로서 LiOH 또는 LiCO3일 수 있다. The PBA particles can be dispersed in an aqueous solution in which the lithium salt is dissolved, filtered and dried to coat the PBA particles with a lithium salt. At this time, the surface and internal pores of the PBA particles may be coated with a lithium salt. The lithium salt may be LiOH or LiCO 3 as an example.
이 후, 리튬염으로 코팅된 PBA 입자들(PBA@리튬염)을 전이금속 전구체 수용액 내에 분산시키고 필터링 및 건조하여 리튬염으로 코팅된 PBA 입자들(PBA@알칼리염)을 다시 전이금속 전구체로 코팅하여 리튬염과 전이금속 전구체로 차례로 코팅된 PBA 입자들(PBA@리튬염@전이금속전구체)을 형성할 수 있다. 이 때, 상기 PBA 입자의 표면 및 내부 기공은 리튬염과 전이금속전구체로 차례로 코팅될 수 있다. 다만, 전이금속 전구체 코팅단계는 경우에 따라서는 생략될 수도 있다.Thereafter, the PBA particles coated with lithium salt (PBA@lithium salt) are dispersed in an aqueous transition metal precursor solution, filtered and dried to coat the PBA particles coated with lithium salt (PBA@alkaline salt) again with a transition metal precursor. By doing so, it is possible to form PBA particles (PBA@lithium salt@transition metal precursor) which are sequentially coated with a lithium salt and a transition metal precursor. At this time, the surface and internal pores of the PBA particles may be coated in turn with a lithium salt and a transition metal precursor. However, the transition metal precursor coating step may be omitted in some cases.
상기 전이금속 전구체는 상기 PBA를 구성하는 전이금속들의 전구체를 포함할 수 있다. 일 예로서, 상기 PBA가 니켈, 망간, 및 코발트를 함유하는 경우, 상기 전이금속 전구체는 니켈 전구체 구체적으로 니켈 질산염 또는 니켈 황산염, 망간 전구체 구체적으로 망간 질산염 또는 망간 황산염, 및 코발트 전구체 구체적으로 코발트 질산염 또는 코발트 황산염를 포함할 수 있다. The transition metal precursor may include precursors of transition metals constituting the PBA. As an example, when the PBA contains nickel, manganese, and cobalt, the transition metal precursor is a nickel precursor specifically nickel nitrate or nickel sulfate, a manganese precursor specifically manganese nitrate or manganese sulfate, and a cobalt precursor specifically cobalt nitrate Or cobalt sulfate.
리튬염과 전이금속 전구체로 차례로 코팅된 PBA 입자들(PBA@리튬염@전이금속전구체)을 공기분위기에서 열분해하여(pyrolysis), PBA 입자들 내에서 전이금속들 사이의 CN 브릿지들을 산화시켜 산소 브릿지들로의 전환시킬 수 있다. 열분해 온도는 약 400도 내지 500도일 수 있고, 열분해 시간은 약 2 내지 4시간일 수 있다.Oxygen bridge by oxidizing CN bridges between transition metals in PBA particles by pyrolysis of PBA particles (PBA@lithium salt@transition metal precursor) coated in sequence with lithium salt and transition metal precursor You can switch to The thermal decomposition temperature may be about 400 to 500 degrees, and the thermal decomposition time may be about 2 to 4 hours.
한편, 상기 열분해 과정에서 전이금속들 사이의 CN 브릿지들을 산화시켜 산소 브릿지들로의 전환되면서 전이금속들 사이의 거리가 가까워져 입자 형상의 붕괴가 일어날 수도 있다. 그러나, 화학식 1로 나타낸 PBA를 형성할 때 숙성시간을 충분히 길게 일 예로서, 앞서 설명한 바와 같이 3 주 내지 5주로 설정하는 경우, PBA 입자 내의 결정결함 발생을 충분히 줄일 수 있어, 상기 열분해 과정에서의 입자 형상의 붕괴를 크게 줄이거나 입자 형상의 붕괴를 막을 수 있다. 또한, 열분해시 승온속도는 0.5 내지 1.5℃/min로 비교적 느리게 진행하여 입자의 형상을 유지할 수 있다.On the other hand, in the thermal decomposition process, the CN bridges between transition metals are oxidized and converted to oxygen bridges, so that the distance between the transition metals becomes close and collapse of the particle shape may occur. However, when forming the PBA represented by Chemical Formula 1, as an example, the aging time is set to 3 weeks to 5 weeks as an example, as described above, it is possible to sufficiently reduce the occurrence of crystal defects in the PBA particles, in the thermal decomposition process. The collapse of the particle shape can be greatly reduced or the collapse of the particle shape can be prevented. In addition, the temperature rise rate during thermal decomposition proceeds relatively slowly to 0.5 to 1.5°C/min to maintain the shape of the particles.
이 후, 산화된 결과물을 하소하여(calcination), 하기 화학식 2로 나타낸 리튬-전이금속 산화물을 형성할 수 있다.Thereafter, the oxidized product is calcined to form a lithium-transition metal oxide represented by Chemical Formula 2 below.
[화학식 2][Formula 2]
Li[M1 xM2 yM3 z]O2 Li[M 1 x M 2 y M 3 z ]O 2
상기 화학식 2에서 M1, M2 및 M3는 서로에 관계없이 Ni, Mn, Co, Fe, Ti, V, 또는 Cr일 수 있다. 상기 화학식 2의 M1, M2 및 M3는 상기 화학식 1의 M1, M2 및 M3와 각각 동일한 전이금속이되 산화수는 동일하거나 동일하지 않을 수 있다. 일 예로서, M1은 Ni일 수 있고, M2는 Mn일 수 있고, M3는 Co일 수 있다. x, y, z는 x+y+z=1을 만족하는 조건에서 0.1 내지 0.8, 0.2 내지 0.6, 또는 0.2 내지 0.4의 값을 가질 수 있다. 이 때, x:y:z의 비는 상기 화학식 1에서의 a:b:c의 비와 같을 수 있다. 그러나, 이에 한정되는 것은 아니다. In Formula 2, M 1 , M 2 and M 3 may be Ni, Mn, Co, Fe, Ti, V, or Cr, regardless of each other. M 1, M 2 and M 3 are M 1, M 2, and are the same oxidation state transition metal, respectively, and M 3 in the formula (1) of the general formula (2) may or may not be equal. As an example, M 1 may be Ni, M 2 may be Mn, and M 3 may be Co. x, y, z may have a value of 0.1 to 0.8, 0.2 to 0.6, or 0.2 to 0.4 in a condition that satisfies x+y+z=1. At this time, the ratio of x:y:z may be the same as the ratio of a:b:c in Chemical Formula 1 above. However, it is not limited thereto.
상기 하소 과정에서 상전이가 일어날 수 있고, 상기 화학식 2로 나타낸 리튬 전이금속 산화물은 전이금속 산화물층과 리튬층이 반복되어 배열된 헥사고날 층상 구조(hexagonal layered structure)를 나타낼 수 있고, 층상구조 중에서도 O3 구조를 나타낼 수 있다. 이러한 리튬 전이금속 산화물 결정에서 c축 길이/a축 길이 즉 XRD 그래프에서 I(003)/I(104)은 1 초과, 나아가 1.2 이상, 더 나아가 1.4 이상, 그리고 1.5 이하의 값을 나타낼 수 있다. 이로써, 리튬 이온 대신 다른 전이금속 양이온(특히 니켈 이온)이 삽입되는 현상인 양이온 혼합(cation mixing)이 억제될 수 있다.During the calcination process, a phase transition may occur, and the lithium transition metal oxide represented by Chemical Formula 2 may exhibit a hexagonal layered structure in which the transition metal oxide layer and the lithium layer are repeatedly arranged, and O3 among the layered structures. Structure. In the lithium transition metal oxide crystal, the c-axis length/a-axis length, that is, I (003) /I (104) in the XRD graph may exhibit a value of more than 1, further 1.2 or more, further 1.4 or more, and 1.5 or less. Thus, cation mixing, which is a phenomenon in which other transition metal cations (especially nickel ions) are inserted instead of lithium ions, can be suppressed.
상기 화학식 2로 나타낸 리튬 전이금속 산화물의 입자의 형상은 사각형으로 둘러싸인 육면체 일 예로서, 정육면체일 수 있다. 이 경우, 입자의 형상이 구형인 경우 대비 동일 부피에서 표면적이 더 커질 수 있다. 이는 반응면적의 증가로 인해 용량의 증가로 나타날 수 있다. 이 때, 정육면체는 모든 변의 길이가 5%의 오차 범위 내에서 동일하고, 모든 각이 5%의 오차 범위 내에서 동일한 것을 의미할 수 있다. 한편, 육면체의 각 변의 길이는 약 50 내지 150nm일 수 있다. The shape of the particles of the lithium transition metal oxide represented by Chemical Formula 2 may be, for example, a cube surrounded by a rectangle, and a cube. In this case, the surface area may be larger at the same volume than when the particle shape is spherical. This can be seen as an increase in capacity due to an increase in the reaction area. At this time, the cube may mean that all sides have the same length within an error range of 5%, and all angles are equal within an error range of 5%. Meanwhile, the length of each side of the cube may be about 50 to 150 nm.
상기 하소는 1차 하소 단계와 2차 하소 단계를 포함할 수 있고, 상기 1차 하소를 종료한 후 상기 2차 하소를 시작하기 전에 상온으로 냉각하는 단계를 포함할 수 있다. 또한 상기 하소는 공기분위기에서 수행될 수 있다. 상기 1차 하소를 위한 온도는 800 내지 900도일 수 있고, 처리 시간은 약 3 내지 6시간일 수 있다. 이 후, 얻어진 결과물인 리튬-전이금속 산화물 파우더를 상온에서 분쇄한 후 상기 2차 하소를 실시할 수 있다. 2차 하소를 위한 온도는 750 내지 850도일 수 있고, 처리 시간은 약 4 내지 5시간일 수 있다. 상기 1차 하소 및 2차 하소에서 승온속도는 4 내지 6℃/min로 비교적 느리게 진행하여 입자의 형상을 유지할 수 있다.The calcination may include a primary calcination step and a secondary calcination step, and may include cooling to room temperature before starting the secondary calcination after terminating the primary calcination. In addition, the calcination can be performed in an air atmosphere. The temperature for the primary calcination may be 800 to 900 degrees, and the treatment time may be about 3 to 6 hours. Thereafter, the obtained resultant lithium-transition metal oxide powder may be ground at room temperature and then subjected to the second calcination. The temperature for the second calcination can be 750 to 850 degrees, and the treatment time can be about 4 to 5 hours. In the first calcination and the second calcination, the temperature increase rate can be relatively slow to 4 to 6°C/min to maintain the shape of the particles.
앞서 설명한 바와 같이, 상기 열분해 과정에서 하소 과정에서 상전이가 일어남에도 불구하고 또한 입자 상에 코팅된 전이금속 전구체는 입자의 형태를 안정적으로 유지할 수 있다. As described above, the transition metal precursor coated on the particles may maintain the shape of the particles stably despite the phase transition during calcination in the thermal decomposition process.
이러한 리튬-전이금속 산화물인 활물질은 후술하는 리튬 이차 전지의 양극 활물질로 사용되어 리튬 이차 전지가 구동될 때에도 입자 구조가 안정적으로 유지될 수 있어 효율이 우수하며 고율 특성이 우수할 수 있다.The active material, which is a lithium-transition metal oxide, is used as a positive electrode active material for a lithium secondary battery, which will be described later, so that the particle structure can be stably maintained even when the lithium secondary battery is driven, so that efficiency and high rate characteristics can be excellent.
리튬 이차 전지Lithium secondary battery
본 발명의 일 실시예에 따른 리튬 이차 전지는 위에서 설명한 활물질을 양극활물로서 함유하는 양극, 리튬 이온이 탈삽입될 수 있는 음극활물질을 함유하는 음극, 및 이들 사이에 위치하는 전해질을 구비할 수 있다.The lithium secondary battery according to an embodiment of the present invention may include a positive electrode containing the active material described above as a positive electrode active material, a negative electrode containing a negative electrode active material capable of deintercalating lithium ions, and an electrolyte positioned therebetween. .
<양극><anode>
상기 양극활물질, 도전재, 및 결합제를 혼합하여 양극재료를 얻을 수 있다. 이 때, 도전재는 천연 흑연, 인조 흑연, 코크스류, 카본 블랙, 탄소 나노튜브, 그라핀 등의 탄소 재료일 수 있다. 결합제는 열가소성 수지 예를 들어, 폴리불화비닐리덴, 폴리테트라플루오로에틸렌, 사불화에틸렌, 불화비닐리덴계 공중합체, 육불화프로필렌 등의 불소 수지, 및/또는 폴리에틸렌, 폴리프로필렌 등의 폴리올레핀 수지를 포함할 수 있다.A positive electrode material may be obtained by mixing the positive electrode active material, a conductive material, and a binder. At this time, the conductive material may be natural graphite, artificial graphite, coke, carbon black, carbon nanotubes, graphene, and other carbon materials. Binders include thermoplastic resins such as polyvinylidene fluoride, polytetrafluoroethylene, ethylene tetrafluoride, vinylidene fluoride copolymers, fluorine resins such as propylene hexafluoride, and/or polyolefin resins such as polyethylene and polypropylene. It can contain.
양극재료를 양극 집전체 상에 도포하여 양극을 형성할 수 있다. 양극 집전체는 Al, Ni, 스테인레스 등의 도전체일 수 있다. 양극재료를 양극 집전체 상에 도포하는 것은 가압 성형, 또는 유기 용매등을 사용하여 페이스트를 만든 후 이 페이스트를 집전체 상에 도포하고 프레스하여 고착화하는 방법을 사용할 수 있다. 유기 용매는 N,N-디메틸아미노프로필아민, 디에틸트리아민 등의 아민계; 에틸렌옥시드, 테트라히드로푸란 등의 에테르계; 메틸에틸케톤 등의 케톤계; 아세트산메틸 등의 에스테르계; 디메틸아세트아미드, N-메틸-2-피롤리돈 등의 비양성자성 극성 용매 등일 수 있다. 페이스트를 양극 집전체 상에 도포하는 것은 예를 들면, 그라비아 코팅법, 슬릿다이 코팅법, 나이프 코팅법, 스프레이 코팅법을 사용하여 수행할 수 있다.The positive electrode material may be coated on the positive electrode current collector to form the positive electrode. The positive electrode current collector may be a conductor such as Al, Ni, and stainless steel. Applying the positive electrode material on the positive electrode current collector may be a method of forming a paste using pressure molding or an organic solvent, and then applying the paste onto the current collector and pressing to fix it. Organic solvents include amines such as N,N-dimethylaminopropylamine and diethyltriamine; Ether systems such as ethylene oxide and tetrahydrofuran; Ketone systems such as methyl ethyl ketone; Ester systems such as methyl acetate; Aprotic polar solvents such as dimethylacetamide and N-methyl-2-pyrrolidone. Applying the paste on the positive electrode current collector can be performed using, for example, a gravure coating method, a slit die coating method, a knife coating method, or a spray coating method.
<음극><cathode>
음극활물질은 리튬 이온을 탈삽입하거나 변환(conversion) 반응을 일으킬 수 있는 금속, 금속합금, 금속산화물, 금속불화물, 금속황화물, 및 천연 흑연, 인조흑연, 코크스류, 카본 블랙, 탄소나노튜브, 그라핀 등의 탄소 재료 등을 사용하여 형성할 수도 있다. The negative electrode active material is a metal, a metal alloy, a metal oxide, a metal fluoride, a metal sulfide, and natural graphite, artificial graphite, coke, carbon black, carbon nanotube, graphene, which can deintercalate or convert lithium ions. It can also be formed using a carbon material such as fin.
음극활물질, 도전재, 및 결합제를 혼합하여 음극재료를 얻을 수 있다. 이 때, 도전재는 천연 흑연, 인조 흑연, 코크스류, 카본 블랙, 탄소 나노튜브, 그라핀 등의 탄소 재료일 수 있다. 결합제는 열가소성 수지 예를 들어, 폴리불화비닐리덴, 폴리테트라플루오로에틸렌, 사불화에틸렌, 불화비닐리덴계 공중합체, 육불화프로필렌 등의 불소 수지, 및/또는 폴리에틸렌, 폴리프로필렌 등의 폴리올레핀 수지를 포함할 수 있다.A negative electrode material can be obtained by mixing a negative electrode active material, a conductive material, and a binder. At this time, the conductive material may be natural graphite, artificial graphite, coke, carbon black, carbon nanotubes, graphene, and other carbon materials. Binders include thermoplastic resins such as polyvinylidene fluoride, polytetrafluoroethylene, ethylene tetrafluoride, vinylidene fluoride copolymers, fluorine resins such as propylene hexafluoride, and/or polyolefin resins such as polyethylene and polypropylene. It can contain.
음극재료를 음극 집전체 상에 도포하여 음극을 형성할 수 있다. 음극 집전체는 Al, Ni, 스테인레스 등의 도전체일 수 있다. 음극재료를 음극 집전체 상에 도포하는 것은 가압 성형, 또는 유기 용매등을 사용하여 페이스트를 만든 후 이 페이스트를 집전체 상에 도포하고 프레스하여 고착화하는 방법을 사용할 수 있다. 유기 용매는 N,N-디메틸아미노프로필아민, 디에틸트리아민 등의 아민계; 에틸렌옥시드, 테트라히드로푸란 등의 에테르계; 메틸에틸케톤 등의 케톤계; 아세트산메틸 등의 에스테르계; 디메틸아세트아미드, N-메틸-2-피롤리돈 등의 비양성자성 극성 용매 등일 수 있다. 페이스트를 음극 집전체 상에 도포하는 것은 예를 들면, 그라비아 코팅법, 슬릿다이 코팅법, 나이프 코팅법, 스프레이 코팅법을 사용하여 수행할 수 있다.The negative electrode material may be coated on the negative electrode current collector to form a negative electrode. The negative electrode current collector may be a conductor such as Al, Ni, and stainless steel. Applying the negative electrode material on the negative electrode current collector may be a method of forming a paste using pressure molding or an organic solvent, and then applying the paste onto the current collector and pressing it to fix it. Organic solvents include amines such as N,N-dimethylaminopropylamine and diethyltriamine; Ether systems such as ethylene oxide and tetrahydrofuran; Ketone systems such as methyl ethyl ketone; Ester systems such as methyl acetate; Aprotic polar solvents such as dimethylacetamide and N-methyl-2-pyrrolidone. Applying the paste on the negative electrode current collector may be performed using, for example, a gravure coating method, a slit die coating method, a knife coating method, or a spray coating method.
<전해질><Electrolyte>
전해질은 라튬염과 이를 용해하는 용매를 함유하는 액체 전해질일 수 있다. 구체적으로, LiCl, LiBr, LiI, LiClO4, LiBF4, LiB10Cl10, LiPF6, LiCH3SO3, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiAlCl4, LiN(SO2CF3)2, 클로로 보란 리튬염, 저급 지방족 카르복실산 리튬염, 4 페닐 붕산 리튬염 등일 수 있고, 또는 이들 중 2종 이상의 혼합물을 사용할 수도 있다. The electrolyte may be a liquid electrolyte containing a lithium salt and a solvent dissolving it. Specifically, LiCl, LiBr, LiI, LiClO 4 , LiBF 4 , LiB 10 Cl 10 , LiPF 6 , LiCH 3 SO 3 , LiCF 3 SO 3 , LiCF 3 CO 2 , LiAsF 6 , LiSbF 6 , LiAlCl 4 , LiN(SO 2 CF 3 ) 2 , a chloro borane lithium salt, a lower aliphatic carboxylic acid lithium salt, a 4 phenyl lithium borate salt, or the like, or a mixture of two or more of them may be used.
상기 용매는 유기 용매일 수 있다.유기 용매로는, 예를 들면 프로필렌카르보네이트, 에틸렌카르보네이트, 디메틸카르보네이트, 디에틸카르보네이트, 에틸메틸카르보네이트, 이소프로필메틸카르보네이트, 비닐렌카르보네이트, 4-트리플루오로메틸-1,3-디옥솔란-2-온, 1,2-디(메톡시카르보닐옥시)에탄 등의 카르보네이트류; 1,2-디메톡시에탄, 1,3-디메톡시프로판, 펜타플루오로프로필메틸에테르, 2,2,3,3-테트라플루오로프로필디플루오로메틸에테르, 테트라히드로푸란, 2-메틸테트라히드로푸란 등의 에테르류; 포름산메틸, 아세트산메틸, γ-부티로락톤 등의 에스테르류; 아세토니트릴, 부티로니트릴 등의 니트릴류; N,N-디메틸포름아미드, N,N-디메틸아세트아미드 등의 아미드류; 3-메틸-2-옥사졸리돈 등의 카르바메이트류; 술포란, 디메틸술폭시드, 1,3-프로판술톤 등의 황 함유 화합물; 또는 상기한 유기 용매에 추가로 불소 치환기를 도입한 것을 사용할 수 있다. The solvent may be an organic solvent. As an organic solvent, for example, propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, isopropyl methyl carbonate , Carbonates such as vinylene carbonate, 4-trifluoromethyl-1,3-dioxolan-2-one and 1,2-di(methoxycarbonyloxy)ethane; 1,2-dimethoxyethane, 1,3-dimethoxypropane, pentafluoropropylmethyl ether, 2,2,3,3-tetrafluoropropyldifluoromethyl ether, tetrahydrofuran, 2-methyltetrahydro Ethers such as furan; Esters such as methyl formate, methyl acetate, and γ-butyrolactone; Nitriles such as acetonitrile and butyronitrile; Amides such as N,N-dimethylformamide and N,N-dimethylacetamide; Carbamates such as 3-methyl-2-oxazolidon; Sulfur-containing compounds such as sulfolane, dimethyl sulfoxide and 1,3-propanesultone; Alternatively, a fluorine substituent introduced into the above-described organic solvent may be used.
그러나, 전해질은 이에 한정되지 않고, 상기 액체 전해질을 고분자 내에 함침시킨 고분자형 고체 전해질 또는 세라믹형 고체 전해질일 수도 있다. 상기 고분자형 고체 전해질에서 고분자는 폴리에틸렌옥시드계의 고분자 화합물, 폴리오르가노실록산쇄 또는 폴리옥시알킬렌쇄 중 적어도 1종 이상을 포함하는 고분자 화합물 등일 수 있다. 상기 세라믹형 고체 전해질은 해당 금속의 황화물, 산화물, 및 인산염화물 등의 무기세라믹을 이용할 수도 있다. 고체 전해질은 후술하는 세퍼레이터의 역할을 하는 경우도 있고, 그 경우에는 세퍼레이터를 필요로 하지 않는 경우도 있다.However, the electrolyte is not limited thereto, and the liquid electrolyte may be a polymer solid electrolyte or a ceramic solid electrolyte impregnated into the polymer. In the polymer-type solid electrolyte, the polymer may be a polymer compound containing at least one of a polyethylene oxide-based polymer compound, a polyorganosiloxane chain, or a polyoxyalkylene chain. The ceramic type solid electrolyte may also use inorganic ceramics such as sulfide, oxide, and phosphate of the metal. The solid electrolyte may serve as a separator to be described later, and in that case, a separator may not be required.
<세퍼레이터><Separator>
양극과 음극 사이에 세퍼레이터가 배치될 수 있다. 이러한 세퍼레이터는 폴리에틸렌, 폴리프로필렌 등의 폴리올레핀 수지, 불소 수지, 질소 함유 방향족 중합체 등의 재질로 이루어지는 다공질 필름, 부직포, 직포 등의 형태를 가지는 재료일 수 있다. 세퍼레이터의 두께는, 전지의 부피 에너지 밀도가 높아지고, 내부 저항이 작아진다는 점에서, 기계적 강도가 유지되는 한 얇을수록 바람직하다.A separator may be disposed between the anode and the cathode. The separator may be a material having a form of a porous film made of a material such as polyethylene, polypropylene, polyolefin resin, fluorine resin, or nitrogen-containing aromatic polymer, nonwoven fabric, woven fabric, or the like. The thickness of the separator is preferably as thin as possible, as long as the mechanical strength is maintained, in that the bulk energy density of the battery increases and the internal resistance decreases.
<리튬 이차 전지의 제조 방법><Method for manufacturing lithium secondary battery>
양극, 세퍼레이터, 및 음극을 순서대로 적층하여 전극군을 형성한 후 필요하다면 전극군을 말아서 전지캔에 수납하고, 전극군에 전해액을 함침시킴으로써 리튬 이차 전지를 제조할 수 있다. 이와는 달리, 양극, 고체 전해질, 및 음극을 적층하여 전극군을 형성한 후 필요하다면 전극군을 말아서 전지캔에 수납하여 금속 이차 전지를 제조할 수 있다.A positive electrode, a separator, and a negative electrode may be stacked in order to form an electrode group, and then, if necessary, the electrode group may be rolled and stored in a battery can, and a lithium secondary battery may be manufactured by impregnating the electrode group with an electrolyte solution. Alternatively, a positive electrode, a solid electrolyte, and a negative electrode may be stacked to form an electrode group, and then, if necessary, the electrode group may be rolled and stored in a battery can to manufacture a metal secondary battery.
이하, 본 발명의 이해를 돕기 위하여 바람직한 실험예(example)를 제시한다. 다만, 하기의 실험예는 본 발명의 이해를 돕기 위한 것일 뿐, 본 발명이 하기의 실험예에 의해 한정되는 것은 아니다.Hereinafter, a preferred experimental example (example) is presented to help understanding of the present invention. However, the following experimental examples are only to aid understanding of the present invention, and the present invention is not limited by the following experimental examples.
<활물질 제조예 1><Active material manufacturing example 1>
PBA 파우더 제조 단계PBA powder manufacturing steps
0.005 mol (1.314 g)의 NiSO4·6H2O, 0.001 mol (0.169 g)의 MnSO4·H2O, 및 0.009 mol (2.6469 g)의 소듐 시트레이트 트라이베이직 다이하이드레이트(Sodium citrate tribasic dihydrate)를 탈이온수 200 ㎖에 넣고 초음파 10분 교반 10분 실시하여 녹였다. 이 용액을, 0.004 mol (1.329 g)의 K3Co(CN)6을 탈이온수 200 ㎖에 넣고 20분간 교반한 용액과 혼합하였다. 혼합액를 약 4주 동안 숙성시킨 후 필터링하여, 프러시안 블루 유사물(Prussian blue analogue; PBA)인 Ni2Mn[Co(CN)6]2을 푸른색의 정육면체 입자 파우더로 얻었다.0.005 mol (1.314 g) NiSO 4 · 6H 2 O, 0.001 mol (0.169 g) MnSO 4 ·H 2 O, and 0.009 mol (2.6469 g) of sodium citrate tribasic dihydrate It was dissolved in 200 ml of deionized water and subjected to 10 minutes of ultrasonic stirring for 10 minutes. This solution was mixed with 0.004 mol (1.329 g) of K 3 Co(CN) 6 in 200 mL of deionized water and stirred for 20 minutes. The mixture was aged for about 4 weeks and filtered to obtain Ni 2 Mn[Co(CN) 6 ] 2 , a Prussian blue analogue (PBA), as a blue cube particle powder.
LiOH 코팅 단계LiOH coating step
LiOH·H2O 0.02 g (0.467 mmol)가 용해된 수용액 내에 상기 PBA 0.05 g (0.415 mmol)을 넣고 교반에 의해 분산시켜 균일한 갈색의 용액을 얻었다. 이를 필터링한 후 110℃ 오븐에서 건조하여 LiOH 코팅된 PBA(PBA@LiOH) 파우더를 얻었다.In the aqueous solution in which 0.02 g (0.467 mmol) of LiOHH 2 O was dissolved, 0.05 g (0.415 mmol) of the PBA was added and dispersed by stirring to obtain a uniform brown solution. After filtering this, it was dried in an oven at 110° C. to obtain a LiOH coated PBA (PBA@LiOH) powder.
전이금속 전구체 코팅 단계Transition metal precursor coating step
0.005 g (0.017 mmol)의 Ni(NO3)2·6H2O, 0.005 g (0.017 mmol)의 Co(NO3)2·6H2O, 그리고 0.003 g (0.018 mmol)의 MnSO4·H2O가 용해된 수용액 내에 상기 PBA@LiOH 파우더 (0.06 g)를 넣고 30초간 교반에 의해 분산시켰다. 이 분산액을 필터링한 후 110℃ 오븐에서 건조하여 LiOH 코팅된 PBA(PBA@LiOH) 상에 Ni 전구체, Co 전구체, 그리고 Mn 전구체가 다시 코팅된 (PBA@LiOH@NCM) 파우더를 얻었다.0.005 g (0.017 mmol) of Ni(NO 3 ) 2 · 6H 2 O, 0.005 g (0.017 mmol) of Co(NO 3 ) 2 ·6H 2 O, and 0.003 g (0.018 mmol) of MnSO 4 ·H 2 O The PBA@LiOH powder (0.06 g) was added to the dissolved solution and dispersed by stirring for 30 seconds. The dispersion was filtered and dried in an oven at 110° C. to obtain a (PBA@LiOH@NCM) powder coated with Ni precursor, Co precursor, and Mn precursor again on LiOH coated PBA (PBA@LiOH).
열처리 단계Heat treatment step
PBA@LiOH@NCM 파우더를 도가니에 담아 공기분위기의 퍼니스에서 450℃까지 1℃/min으로 3시간 동안 처리하여 PBA 내의 CN 리간드들을 산화한 후, 다시 850℃까지 5℃/min으로 5시간 동안 처리해 주었다. 이 후, 파우더를 분쇄한 후, 다시 800℃까지 5℃/min으로 5시간 동안 추가 열처리를 하여, Li[Ni0.4Co0.4Mn0.2]O2 파우더를 얻었다.PBA@LiOH@NCM powder in a crucible was treated in a furnace in an air atmosphere at 450°C for 1 hour/min for 3 hours to oxidize CN ligands in the PBA, and then for 5 hours at 5°C/min up to 850°C gave. Thereafter, after pulverizing the powder, further heat treatment was performed at 5°C/min for 5 hours to 800°C to obtain a Li[Ni 0.4 Co 0.4 Mn 0.2 ]O 2 powder.
<활물질 제조예 2><Active material manufacturing example 2>
전이금속 전구체 코팅단계를 생략한 것을 제외하고는 활물질 제조예와 동일한 방법으로 활물질(Li-NCM 산화물)을 제조하였다.An active material (Li-NCM oxide) was prepared in the same manner as the active material preparation example, except that the transition metal precursor coating step was omitted.
<활물질 비교예 1><Active material comparative example 1>
LiOH 코팅단계와 전이금속 전구체 코팅단계를 생략하고, 열처리 단계에서 850℃까지 5℃/min으로 5시간 열처리 대신 800℃까지 5℃/min으로 3시간 열처리한 것을 제외하고는 활물질 제조예와 동일한 방법으로 활물질(NCM 산화물)을 제조하였다.The same method as in the active material preparation example except that the LiOH coating step and the transition metal precursor coating step were omitted, and the heat treatment step was heat treated at 5°C/min for 5 hours at 5°C/min to 850°C, instead of heat treatment at 800°C for 5 hours at 5°C/min. As an active material (NCM oxide) was prepared.
<활물질 비교예 2> <Active material comparative example 2>
PBA 파우더를 제조할 때 4주 동안 숙성시키는 대신 2주 동안 숙성시켜 PBA 파우더를 제조한 후, LiOH 코팅단계와 전이금속 전구체 코팅단계를 생략하고, 열처리 단계에서 850℃까지 5℃/min으로 5시간 열처리 대신 800℃까지 5℃/min으로 3시간 열처리한 것을 제외하고는 활물질 제조예와 동일한 방법으로 활물질(NCM 산화물)을 제조하였다.When preparing PBA powder, instead of aging for 4 weeks, aging for 2 weeks to prepare PBA powder, the LiOH coating step and the transition metal precursor coating step are omitted, and the heat treatment step is 850°C to 5°C/min for 5 hours. An active material (NCM oxide) was prepared in the same manner as the active material manufacturing example, except that the heat treatment was performed at 5°C/min for 3 hours to 800°C instead of the heat treatment.
PBA 파우더 제조 단계PBA powder manufacturing steps LiOH 코팅 단계LiOH coating step 전이금속 전구체코팅 단계Transition metal precursor coating step 열처리 단계Heat treatment step
활물질 제조예1Active material preparation example 1 4주 숙성4 weeks aged ○○ ○○ ○450℃ 3h/ 850℃ 5h/ 800℃5h○450℃ 3h/ 850℃ 5h / 800℃5h
활물질 제조예2Active material preparation example 2 4주 숙성4 weeks aged ○○ -- ○450℃ 3h/ 850℃ 5h/ 800℃5h○450℃ 3h/ 850℃ 5h / 800℃5h
활물질 비교예1Active material comparative example 1 4주 숙성4 weeks aged -- -- ○450℃ 3h/ 800℃ 3h/ 800℃5h○450℃ 3h/ 800℃ 3h / 800℃5h
활물질 비교예2Active material comparative example 2 2주 숙성2 weeks aged -- -- ○450℃ 3h/ 800℃ 3h/ 800℃5h○450℃ 3h/ 800℃ 3h / 800℃5h
도 2는 활물질 제조예 1에 따른 활물질을 촬영한 SEM(scanning electron microscope) 사진들을 나타내고, 도 3은 활물질 제조예 2에 따른 활물질을 촬영한 SEM 사진들을 나타낸다. 또한, 도 4는 활물질 비교예 1에 따른 활물질을 촬영한 SEM 사진을 나타내고, 도 5는 활물질 비교예 2에 따른 활물질을 촬영한 SEM 사진을 나타낸다.도 5를 참조하면, 활물질 비교예 2에 따른 활물질은 소성 후 많은 결함들이 발생한 것을 알 수 있다. 이는 PBA 파우더 제조단계에서의 숙성 시간 즉, 공침법에 따른 합성시간이 짧아 PBA 내의 결정결함들이 다수 발생하였기 때문에, 소성단계에서 CN 리간드들이 산화되면서 CN 브릿지들이 산소 브릿지들로 전환될 때 금속들 사이의 간격이 좁아지고 또한 오스트발드 라이프닝(Ostwald ripening) 현상에 따라 구조유지가 어려웠기 때문으로 추정되었다.2 shows SEM (scanning electron microscope) photographs of the active material according to Preparation Example 1, and FIG. 3 shows SEM photographs of the active material according to Preparation Example 2. In addition, FIG. 4 shows an SEM photograph of an active material according to Comparative Example 1 of the active material, and FIG. 5 shows an SEM photograph of an active material according to Comparative Example 2 of the active material. It can be seen that many defects occurred in the active material after firing. This is because the aging time in the PBA powder manufacturing step, that is, the synthesis time according to the co-precipitation method is short, so many crystal defects in the PBA occur, and when the CN ligands are oxidized in the firing step, the CN bridges are converted into oxygen bridges. The gap was narrowed and it was estimated that the structure was difficult to maintain due to the Ostwald ripening phenomenon.
도 4를 참조하면, 활물질 비교예 1에 따른 활물질은 소성 후에도 정육면체의 입자 형태를 유지하고 있음을 알 수 있다. 이는 활물질 비교예 2와는 달리 숙성 시간이 크게 늘어나 PBA 내에 결정결함 형성을 최소화하였기 때문에, 소성과정에서 나타나는 CN 리간드들의 산화에 따른 CN 브릿지들이 산소 브릿지들로의 전환, 이에 따른 금속들 사이의 간격이 축소, 그리고 오스트발드 라이프닝 현상에도 불구하고 입자 구조가 유지되었기 때문으로 추정되었다. 또한, 입자 크기 또한 활물질 비교예 2에 따른 활물질 입자 대비 커진 것을 알 수 있는데, 이는 결정성장이 충분히 이루어졌기 때문으로 판단되었다.Referring to FIG. 4, it can be seen that the active material according to the comparative example 1 of the active material maintains the particle shape of the cube even after firing. This is because, unlike the comparative example 2 of the active material, the aging time was greatly increased to minimize the formation of crystal defects in the PBA, so the CN bridges due to oxidation of the CN ligands appearing in the firing process are converted into oxygen bridges, and thus the interval between the metals is It was presumed that the particle structure was maintained despite the shrinking and Ostwald life. In addition, it can be seen that the particle size is also larger than the active material particles according to Comparative Example 2, which was judged because the crystal growth was sufficiently achieved.
한편, 활물질 비교예 1과 활물질 비교예 2에 따른 활물질은 450℃ 3시간 열처리(첫번째), 800℃ 3 시간 열처리(두번째), 그리고 800℃ 5 시간 열처리(세번째)를 진행하였다. 그러나, 상기 두번째 열처리를 활물질 제조예 1과 동일하게 850℃ 5 시간 열처리한 경우에는 활물질 비교예 1과 같이 숙성시간이 2주로 짧은 경우 구조의 붕괴가 더 심하게 발생하거나 혹은 활물질 비교예 2와 같이 숙성시간이 4주로 늘린 경우에도 구조 붕괴가 관찰되었다.On the other hand, the active material according to Comparative Example 1 and Active Material Comparative Example 2 was subjected to heat treatment at 450° C. for 3 hours (first), heat treatment at 800° C. for 3 hours (second), and heat treatment at 800° C. for 5 hours (third). However, when the second heat treatment is heat treated at 850° C. for 5 hours as in the case of the active material preparation example 1, when the aging time is short as 2 weeks as in the active material comparative example 1, the collapse of the structure occurs more severely or it is aged as in the active material comparative example 2 Even when the time was increased to 4 weeks, structural collapse was observed.
도 2를 참조하면, 활물질 제조예 1에 따른 활물질은 열처리 단계 후에도 입자의 형태 즉, 정육면체 형상을 비교적 깨끗하게 유지하고 있는 것을 알 수 있다. 입자를 보다 확대한 사진(b)에서는 입자의 1변의 길이는 약 1um인 것으로 판단되며, 입자 표면에 불규칙한 육면체 형상의 나노사이즈 입자들이 확인되는데, 이로부터 활물질 제조예 1에 따른 활물질은 나노사이즈의 1차 입자가 모여서 생성된 2차 입자임을 알 수 있다. Referring to FIG. 2, it can be seen that the active material according to the active material preparation example 1 relatively maintains the shape of the particles, that is, the shape of the cube, even after the heat treatment step. In the enlarged photo (b) of the particle, it is determined that the length of one side of the particle is about 1 um, and irregular hexahedral nanoparticles on the surface of the particle are identified. From this, the active material according to Preparation Example 1 of the active material is nano-sized. It can be seen that the primary particles are secondary particles generated by aggregation.
도 3을 참조하면, 활물질 제조예 2에 따른 활물질은 활물질 제조예 1(도 2) 대비 입자 형상이 다소 붕괴된 것을 확인할 수 있는데, 이는 제조과정에서 전이금속전구체를 추가하지 않고 열처리 과정(450℃ 3시간 열처리(첫번째), 850℃ 5 시간 열처리(두번째), 그리고 800℃ 5 시간 열처리(세번째))을 진행하였기 때문으로 추정되었다. 이러한 결과로부터, 활물질 제조과정에서 전이금속 전구체를 추가한 후 열처리과정을 진행하는 경우 입자구조의 붕괴를 억제할 수 있음을 알 수 있다.Referring to FIG. 3, it can be seen that the active material according to the active material preparation example 2 has a somewhat collapsed particle shape compared to the active material production example 1 (FIG. 2 ), which is a heat treatment process (450° C.) without adding a transition metal precursor in the manufacturing process. It was estimated that 3 hours heat treatment (first), 850°C 5 hours heat treatment (second), and 800°C 5 hours heat treatment (third) were performed. From these results, it can be seen that when the transition metal precursor is added in the active material manufacturing process and then the heat treatment process is performed, the collapse of the particle structure can be suppressed.
도 6은 활물질 제조예 1에서 얻어진 활물질에 대한 XRD 패턴을 나타낸다.6 shows an XRD pattern for the active material obtained in Preparation Example 1 active material.
도 6을 참조하면, 활물질 제조예 1에서 얻어진 활물질의 XRD 패턴은 (003) 피크와 (104) 피크를 나타내며, (003) 피크의 세기(I003)는 (104) 피크의 세기(I104)에 비해 더 큰 값을 나타냄을 알 수 있다. 다시 말해서, I003/I104의 비가 1 초과, 나아가 1.2 이상, 더 나아가 1.4 이상, 그리고 1.5 이하 구체적으로는 1.47의 값을 나타낸다. I003/I104의 비는 리튬 이온 자리에 리튬 이온 대신 다른 전이금속 양이온(특히 니켈 이온)이 삽입되는 현상인 양이온 혼합(cation mixing)을 판단할 수 있는 지표로서, I003/I104의 비가 1 초과인 경우 양이온 혼합이 낮아지고 나아가 1.2 이상일 때 양이온 혼합이 충분히 낮아지는 것으로 알려져 있다. 따라서, 활물질 제조예 1에 따른 활물질은 양이온 혼합 현상이 충분히 억제된 것을 알 수 있으며 또한 이로 인해 용량과 효율이 향상될 수 있을 것으로 추정되었다.Referring to FIG. 6, the XRD pattern of the active material obtained in Preparation Example 1 shows (003) peak and (104) peak, and (003) peak intensity (I 003 ) is (104) peak intensity (I 104 ) It can be seen that it shows a larger value than. In other words, the ratio of I 003 /I 104 is greater than 1, furthermore 1.2 or more, further 1.4 or more, and 1.5 or less Specifically, it represents a value of 1.47. The ratio of I 003 /I 104 is an index for determining cation mixing, which is a phenomenon in which other transition metal cations (especially nickel ions) are inserted instead of lithium ions at the lithium ion site, and the ratio of I 003 /I 104 It is known that when it is more than 1, cation mixing becomes low, and further, when it is 1.2 or more, cation mixing becomes sufficiently low. Accordingly, it can be seen that the active material according to the active material preparation example 1 sufficiently suppressed the cation mixing phenomenon, and it was estimated that capacity and efficiency could be improved.
<반전지 제조예 1><Half-cell manufacturing example 1>
활물질 제조예 1에서 제조된 활물질, 카본블랙, 및 PVDF(Poly vinylidene fluoride)를 96:2:2의 중량비로 유기 용매(NMP(N-Methyl-2-Pyrrolidone)) 내에서 혼합한 후, 알루미늄 집전체 상에 코팅한 후 프레스하여 양극을 형성하였다. 이 후, 금속 리튬을 음극으로 사용하였고, 유리 필터를 분리막으로 사용하고, 에틸렌 카보네이트(EC, 50vol.%)와 에틸메틸 카보네이트(EMC, 50vol.%)의 혼합 유기용매 내에 전해질 LiPF6(1M)을 함유하는 비수전해액을 사용하여 반전지를 제조하였다.After mixing the active material, carbon black, and PVDF (Poly vinylidene fluoride) prepared in Active Example 1 in a weight ratio of 96:2:2 in an organic solvent (NMP(N-Methyl-2-Pyrrolidone)), the aluminum house After coating on the whole, it was pressed to form an anode. Thereafter, lithium metal was used as a negative electrode, a glass filter was used as a separator, and electrolyte LiPF 6 (1M) in a mixed organic solvent of ethylene carbonate (EC, 50 vol.%) and ethylmethyl carbonate (EMC, 50 vol.%) was used. Semi-prepared paper was prepared using a non-aqueous electrolyte solution containing.
<반전지 비교예 1><Comparative battery 1>
활물질 제조예 1에서 제조된 양극 활물질 대신에 활물질 비교예 1에서 제조된 활물질을 양극 활물질로 사용하는 것을 제외하고는 반전지 제조예와 동일한 과정을 거처 반전지를 제조하였다.A semi-prepared paper was manufactured through the same process as the semi-prepared paper manufacturing example, except that the active material prepared in Comparative Example 1 was used as the positive electrode active material instead of the positive electrode active material prepared in Preparation Example 1.
<반전지 비교예 2><Comparative Example 2 of half battery>
활물질 제조예 1에서 제조된 양극 활물질 대신에 활물질 비교예 2에서 제조된 활물질을 양극 활물질로 사용하는 것을 제외하고는 반전지 제조예와 동일한 과정을 거처 반전지를 제조하였다.A semi-prepared paper was prepared through the same process as the semi-prepared paper manufacturing example, except that the active material prepared in Comparative Example 2 was used as the positive electrode active material instead of the positive electrode active material prepared in Preparation Example 1.
도 7은 반전지 제조예 1, 반전지 비교예 1, 및 반전지 비교에 2에 따른 반전지들의 첫 번째 사이클에서의 충방전 특성을 나타낸 그래프이다. 이 때, 충전은 0.1C로 4.4V까지, 방전은 0.1C로 3.0V까지 행하면서 용량을 측정하였다. 7 is a graph showing charging and discharging characteristics in the first cycle of the reverse cells according to Comparative Example 1, Semi-Compared Paper Comparative Example 1, and Comparative Paper 2. At this time, the capacity was measured while charging was performed at 0.1C to 4.4V and discharge was performed at 0.1C to 3.0V.
하기 표 2에서 반전지 제조예 1, 반전지 비교예 1, 및 반전지 비교에 2에 따른 반전지들의 첫 번째 사이클에서의 충방전 특성을 정리하였다. In Table 2 below, the charging and discharging characteristics in the first cycle of the half cells according to Preparation Example 1, Comparative Example 1, and Comparative Example 2 are summarized.
0.1C 충전(mAh/g)0.1C charge (mAh/g) 0.1C 방전(mAh/g)0.1C discharge (mAh/g) 1st 사이클 효율(%)1 st cycle efficiency (%)
반전지 제조예 1Reverse Paper Manufacturing Example 1 193.26193.26 166.51166.51 86.286.2
반전지 비교예 1Comparative paper 1 217.82217.82 180.28180.28 82.882.8
반전지 비교에 22 for comparison 200.83200.83 173.63173.63 86.586.5
도 7 및 표 2를 참조하면, 반전지 제조예 1에 따른 반전지 즉, 활물질 제조예1에 따른 활물질을 사용한 반전지는, 반전지 비교예들에 따른 반전지들 즉, 활물질 비교예들에 따른 활물질을 사용한 반전지들에 비해 초기 충전 용량 및 방전 용량은 비교적 낮은 반면 충전용량/방전용량의 비 즉, 사이클 효율은 우수하다. 이는 활물질 비교예들에 따른 활물질이 앞서 설명한 바와 같이 입자 구조의 붕괴에 따른 다공성의 증가로 인해 용량은 증가하였으나 효율이 저하되었기 때문으로 추정되었고, 활물질 제조예 1에 따른 활물질은 입자 구조 내에 다공성은 적으나 안정적으로 유지될 수 있기 때문에 용량은 비교적 적으나 효율은 우수한 것으로 추정되었다.Referring to FIGS. 7 and 2, a half-sheet according to Preparation Example 1, that is, a half-sheet using the active material according to Preparation Example 1, a half-sheet according to Comparative Examples, and an active material according to Comparative Examples The initial charge capacity and discharge capacity are relatively low compared to the reverse cells using, while the ratio of charge capacity/discharge capacity, that is, cycle efficiency is excellent. This was estimated because the capacity of the active material according to Comparative Examples increased due to the increase in porosity due to the collapse of the particle structure as described above, but the efficiency decreased. It was estimated that the capacity was relatively small, but the efficiency was excellent because it could be kept stable.
도 8은 반전지 제조예 1, 반전지 비교예 1, 및 반전지 비교에 2에 따른 반전지들의 율속(c-rate)에 따른 방전용량 변화를 나타낸 그래프이다. 이 때, 1-3 번째 사이클은 0.1C, 0.2C, 0.5C에서 4-6 번째 사이클은 1C에서 7-9 번째 사이클은 2C에서 10-12 번째 사이클은 4C에서 그리고 13-15 번째 사이클은 다시 1C에서 4.4V까지 충전과 3.0V까지 방전을 반복하였다.Figure 8 is a graph showing the discharge capacity change according to the rate of crate (c-rate) of the half-cell according to Comparative Example 1, half-cell comparison Example 1, and half-cell comparison. At this time, the 1st to 3rd cycles are 0.1C, 0.2C, and the 4th to 6th cycles at 0.5C, the 7th to 9th cycles at 2C, the 10th to 12th cycles at 4C, and the 13th to 15th cycles again. Charging from 1C to 4.4V and discharging to 3.0V were repeated.
하기 표 3에서 반전지 제조예 1, 반전지 비교예 1, 및 반전지 비교에 2에 따른 반전지들의 율속에 따른 방전용량을 정리하였다. In Table 3 below, the discharge capacity according to the rate of the reverse cells according to Preparation Example 1, Comparative Example 1, and Comparison 2 of the reversed paper was summarized.
방전용량 (mAh/g)Discharge capacity (mAh/g) 4C:1C(%)4C: 1C (%)
0.1C0.1C 0.2C 0.2C 0.5C0.5 C 1C 1C 2C2C 4C4C 1C1C
반전지 제조예 1Reverse Paper Manufacturing Example 1 166.5166.5 158.4158.4 153.0153.0 147.0147.0 130.0130.0 117.7117.7 141.0141.0 83.583.5
반전지 비교예 1Comparative paper 1 180.3180.3 170.3170.3 165.1165.1 161.2161.2 143.4143.4 127.5127.5 157.5157.5 81.081.0
반전지 비교에 22 for comparison 173.8173.8 168.3168.3 161.8161.8 153.3153.3 140.1140.1 113.8113.8 151.2151.2 75.375.3
도 8 및 표 3을 참조하면, 반전지 제조예 1에 따른 반전지 즉, 활물질 제조예1에 따른 활물질을 사용한 반전지는, 반전지 비교예들에 따른 반전지들 즉, 활물질 비교예들에 따른 활물질을 사용한 반전지들에 비해 고율 특성 즉, 1C에서의 방전용량 대비 4C에서의 방전용량의 비가 우수하다. 이는 앞서 도 6 및 표 2를 참조하여 설명한 바와 같이, 활물질 제조예 1에 따른 활물질은 입자 구조가 안정적으로 유지될 수 있기 때문에 고율 특성이 우수한 것으로 추정되었다. Referring to Figure 8 and Table 3, the reverse paper according to Preparation Example 1, that is, the reverse material using the active material according to Preparation Example 1, the reverse paper according to the comparison examples of the reverse paper, that is, the active material according to the comparative examples Compared to the half-cells using high-rate characteristics, that is, the ratio of the discharge capacity at 4C to the discharge capacity at 1C is excellent. As described above with reference to FIGS. 6 and 2, the active material according to the active material preparation example 1 was estimated to have excellent high rate characteristics because the particle structure can be stably maintained.
이상, 본 발명을 바람직한 실시예를 들어 상세하게 설명하였으나, 본 발명은 상기 실시예에 한정되지 않고, 본 발명의 기술적 사상 및 범위 내에서 당 분야에서 통상의 지식을 가진 자에 의하여 여러가지 변형 및 변경이 가능하다.As described above, the present invention has been described in detail with reference to preferred embodiments, but the present invention is not limited to the above embodiments, and various modifications and alterations by those skilled in the art within the technical spirit and scope of the present invention This is possible.

Claims (18)

  1. 하기 화학식 1로 나타낸 프러시안 블루 아날로그(prussian blue analogue; 이하 PBA라고 한다) 입자들을 형성하는 단계;Forming prussian blue analogue (hereinafter referred to as PBA) particles represented by Chemical Formula 1 below;
    상기 PBA 입자들을 리튬염이 용해된 수용액 내에 분산시키고 필터링 및 건조하여, 상기 PBA 입자들을 리튬염으로 코팅하는 단계; Dispersing the PBA particles in an aqueous solution in which the lithium salt is dissolved, filtering and drying, coating the PBA particles with a lithium salt;
    상기 리튬염으로 코팅된 PBA 입자들을 공기분위기에서 열분해하여(pyrolysis)하여 PBA 내의 CN 브릿지들을 산소 브릿지들로 산화하는 단계;Oxidizing the CN bridges in the PBA to oxygen bridges by pyrolysis of the PBA particles coated with the lithium salt in an air atmosphere;
    상기 산화 단계를 거친 결과물을 하소하여(calcination) 리튬-전이금속 산화물을 얻는 단계를 포함하는 리튬-전이금속 산화물 제조 방법:Method for producing a lithium-transition metal oxide comprising the step of calcining the result of the oxidation step to obtain a lithium-transition metal oxide:
    [화학식 1][Formula 1]
    M1 aM2 b[M3(CN)6]c M 1 a M 2 b [M 3 (CN) 6 ] c
    상기 화학식 1에서, M1 및 M2는 2가의 산화수를 갖는 전이금속으로 서로에 관계없이 Ni, Mn, Co, Fe, Ti, V, 또는 Cr이고, M3는 3가의 산화수를 갖는 전이금속으로 Ni, Mn, Co, Fe, Ti, V, 또는 Cr이고, c은 1 내지 5이고, a와 b는 상기 화학식 1의 화합물을 전기적으로 중성이 되도록 하는 양의 값을 갖는다.In Chemical Formula 1, M 1 and M 2 are transition metals having a divalent oxidation number and are Ni, Mn, Co, Fe, Ti, V, or Cr regardless of each other, and M 3 is a transition metal having a trivalent oxidation number. Ni, Mn, Co, Fe, Ti, V, or Cr, c is 1 to 5, and a and b have positive values to make the compound of Formula 1 electrically neutral.
  2. 청구항 1에서,In claim 1,
    상기 PBA 입자들은, The PBA particles,
    제1 전이금속(상기 화학식 1에서 정의된 M1)의 염과 제2 전이금속(상기 화학식 1에서 정의된 M2)의 염의 수용액을 K3M3(CN)6 (M3는 상기 화학식 1에서 정의된 바와 같음)의 수용액과 혼합한 후 혼합용액을 숙성시켜 침전물을 형성하고, 침전물을 필터링하여 얻는 리튬-전이금속 산화물 제조 방법.A first transition metal salt and a second transition metal (the M 1 defined in Formula 1), the salt water (the M 2 defined in formula (I)), K 3 M 3 (CN) 6 (M 3 is the general formula (1) After mixing with an aqueous solution of (as defined in), aging the mixed solution to form a precipitate, and the method for producing a lithium-transition metal oxide obtained by filtering the precipitate.
  3. 청구항 2에서,In claim 2,
    상기 제1 전이금속의 염과 상기 제2 전이금속의 염의 수용액은 구연산 나트륨(sodium citrate)을 더 포함하는 리튬-전이금속 산화물 제조 방법.The first transition metal salt and the aqueous solution of the second transition metal salt further comprises sodium citrate (sodium citrate) lithium-transition metal oxide production method.
  4. 청구항 1에서,In claim 1,
    상기 리튬염은 LiOH인 리튬-전이금속 산화물 제조 방법.The lithium salt is LiOH lithium-transition metal oxide manufacturing method.
  5. 청구항 1에서,In claim 1,
    상기 리튬염으로 코팅된 PBA 입자들을 열분해하기 전에,Before thermally decomposing PBA particles coated with the lithium salt,
    상기 리튬염으로 코팅된 PBA 입자들을 전이금속 전구체 수용액 내에 분산시키고 필터링 및 건조하여 리튬염과 전이금속 전구체로 차례로 코팅된 PBA 입자들을 형성하는 단계를 더 포함하되,The method further includes dispersing the PBA particles coated with the lithium salt in an aqueous transition metal precursor solution, filtering and drying to form PBA particles coated with a lithium salt and a transition metal precursor in turn.
    상기 전이금속 전구체는 상기 PBA를 구성하는 전이금속들의 전구체를 포함하는 리튬-전이금속 산화물 제조 방법.The transition metal precursor is a lithium-transition metal oxide production method comprising a precursor of the transition metals constituting the PBA.
  6. 청구항 1에서,In claim 1,
    상기 열분해 온도는 400도 내지 500도인 리튬-전이금속 산화물 제조 방법. The pyrolysis temperature is 400 degrees to 500 degrees lithium-transition metal oxide production method.
  7. 청구항 1에서,In claim 1,
    상기 하소 단계에서 상전이가 발생하고,Phase transition occurs in the calcination step,
    상기 하소 단계는 1차 하소 단계와 2차 하소 단계를 포함하고,The calcination step includes a first calcination step and a second calcination step,
    상기 1차 하소 단계와 상기 2차 하소 단계 사이에 냉각 단계를 포함하는 리튬-전이금속 산화물 제조 방법.A method for producing a lithium-transition metal oxide comprising a cooling step between the first calcination step and the second calcination step.
  8. 청구항 7에서,In claim 7,
    상기 1차 하소는 800 내지 900도에서 수행하고,The primary calcination is performed at 800 to 900 degrees,
    상기 2차 하소는 750 내지 850도에서 수행하는 리튬-전이금속 산화물 제조 방법.The secondary calcination is a lithium-transition metal oxide production method performed at 750 to 850 degrees.
  9. 청구항 1에서,In claim 1,
    상기 리튬-전이금속 산화물은 하기 화학식 2로 나타낸 리튬-전이금속 산화물 제조 방법.The lithium-transition metal oxide is a lithium-transition metal oxide production method represented by the following formula (2).
    [화학식 2][Formula 2]
    Li[M1 xM2 yM3 z]O2 Li[M 1 x M 2 y M 3 z ]O 2
    상기 화학식 2에서 M1, M2 및 M3는 상기 화학식 1의 M1, M2 및 M3와 각각 동일한 전이금속이되 산화수는 동일하거나 동일하지 않고, x, y, z는 x+y+z=1을 만족하는 조건에서 0.1 내지 0.8의 값을 갖는다.In Formula 2 M 1, M 2 and M 3 are not the same, M 1, M 2, and are oxidation number is the same transition metal, respectively, and M 3 in the formula (1) or the same, x, y, z is x + y + It has a value of 0.1 to 0.8 in a condition that satisfies z=1.
  10. 청구항 9에서,In claim 9,
    상기 화학식 2에서 x:y:z의 비는 상기 화학식 1에서의 a:b:c의 비와 같은 리튬-전이금속 산화물 제조 방법.In the formula (2), the ratio of x:y:z is the same as the ratio of a:b:c in the formula (1).
  11. 청구항 1에서,In claim 1,
    상기 리튬 전이금속 산화물은 전이금속 산화물층과 리튬층이 반복되어 배열된 헥사고날 층상 구조(hexagonal layered structure)를 나타내고,The lithium transition metal oxide represents a hexagonal layered structure in which the transition metal oxide layer and the lithium layer are arranged repeatedly.
    상기 리튬 전이금속 산화물의 결정에서 c축 길이는 a축 길이에 비해 큰 리튬-전이금속 산화물 제조 방법.In the crystal of the lithium transition metal oxide, the c-axis length is larger than the a-axis length.
  12. 청구항 11에서,In claim 11,
    상기 리튬 전이금속 산화물의 결정에서 c축 길이/a축 길이는 1.4 내지 1.5의 값을 나타내는 리튬-전이금속 산화물 제조 방법.In the crystal of the lithium transition metal oxide, the c-axis length/a-axis length represents a value of 1.4 to 1.5.
  13. 청구항 1에서,In claim 1,
    상기 리튬-전이금속 산화물의 입자의 형상은 정육면체인 리튬-전이금속 산화물 제조 방법.The shape of the lithium-transition metal oxide particles is a cube-shaped lithium-transition metal oxide manufacturing method.
  14. 입자의 형상이 정육면체이고 하기 화학식 2로 나타내어지는 리튬-전이금속 산화물:Lithium-transition metal oxide represented by the following formula (2) in the shape of a cube and a particle:
    [화학식 2][Formula 2]
    Li[M1 xM2 yM3 z]O2 Li[M 1 x M 2 y M 3 z ]O 2
    상기 화학식 2에서 M1, M2 및 M3는 서로에 관계없이 Ni, Mn, Co, Fe, Ti, V, 또는 Cr이고, x, y, z는 x+y+z=1을 만족하는 조건에서 0.1 내지 0.8의 값을 갖는다.In Formula 2, M 1 , M 2 and M 3 are Ni, Mn, Co, Fe, Ti, V, or Cr regardless of each other, and x, y, and z satisfy x+y+z=1 It has a value of 0.1 to 0.8.
  15. 청구항 14에서,In claim 14,
    상기 화학식 2로 나타낸 리튬 전이금속 산화물은 전이금속 산화물층과 리튬층이 반복되어 배열된 헥사고날 층상 구조(hexagonal layered structure)를 나타내고,The lithium transition metal oxide represented by Chemical Formula 2 represents a hexagonal layered structure in which the transition metal oxide layer and the lithium layer are arranged repeatedly.
    상기 리튬 전이금속 산화물의 결정에서 c축 길이는 a축 길이에 비해 큰 리튬-전이금속 산화물.In the crystal of the lithium transition metal oxide, the c-axis length is larger than that of the a-axis lithium-transition metal oxide.
  16. 청구항 15에서,In claim 15,
    상기 리튬 전이금속 산화물의 결정에서 c축 길이/a축 길이는 1.4 내지 1.5의 값을 나타내는 리튬-전이금속 산화물.In the crystal of the lithium transition metal oxide, the c-axis length/a-axis length is a lithium-transition metal oxide having a value of 1.4 to 1.5.
  17. 청구항 14에서,In claim 14,
    상기 화학식 2에서 M1은 Ni, M2는 Mn, 그리고 M3는 Co인 리튬-전이금속 산화물.In Formula 2, M 1 is Ni, M 2 is Mn, and M 3 is Co—a lithium-transition metal oxide.
  18. 청구항 14 내지 청구항 17 중 어느 하나의 청구항에 정의된 리튬-전이금속 산화물인 양극활물질을 포함하는 양극;A positive electrode comprising a positive electrode active material that is a lithium-transition metal oxide as defined in any one of claims 14 to 17;
    음극활물질을 함유하는 음극; 및A negative electrode containing a negative electrode active material; And
    상기 양극과 상기 음극 사이에 배치된 전해질을 포함하는 리튬 이차 전지.A lithium secondary battery comprising an electrolyte disposed between the positive electrode and the negative electrode.
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