WO2014098007A1 - Electrode material, electricity storage device provided with electrode material, and method for producing electrode material - Google Patents

Electrode material, electricity storage device provided with electrode material, and method for producing electrode material Download PDF

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WO2014098007A1
WO2014098007A1 PCT/JP2013/083568 JP2013083568W WO2014098007A1 WO 2014098007 A1 WO2014098007 A1 WO 2014098007A1 JP 2013083568 W JP2013083568 W JP 2013083568W WO 2014098007 A1 WO2014098007 A1 WO 2014098007A1
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electrode
electrode material
cobalt oxide
lithium cobalt
carbon material
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PCT/JP2013/083568
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French (fr)
Japanese (ja)
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智志 久保田
修一 石本
賢次 玉光
勝彦 直井
和子 直井
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日本ケミコン株式会社
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • 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
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • 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 an electrode material in which an electrode active material is supported on a carbon material, a method for producing the electrode material, and an electricity storage device including the electrode material.
  • lithium cobalt oxide is used as the electrode active material.
  • Lithium ion secondary batteries that use non-aqueous electrolytes with high energy density are widely used as the power source for information devices such as mobile phones and laptop computers.
  • the performance of these information devices and the amount of information handled In order to cope with an increase in power consumption associated with an increase in the energy consumption, an improvement in the energy density of the lithium ion secondary battery is desired.
  • low-emission vehicles such as electric vehicles and hybrid vehicles that replace gasoline and teal vehicles. Expectations are increasing, and it is desired to develop a large lithium ion secondary battery having a high energy density as a motor drive power source for these low-pollution vehicles.
  • Patent Document 1 discloses a secondary battery using LiCoO 2 as a positive electrode active material and carbon as a negative electrode.
  • Patent Document 2 discloses a lithium ion secondary battery in which lithium cobaltate powder has a particle size distribution of 1 to 40 ⁇ m and a specific range such as an average particle size of 5 to 15 ⁇ m in order to improve charge / discharge characteristics such as rate characteristics. It is disclosed.
  • lithium cobaltate which is a positive electrode active material as described above
  • the output characteristics of lithium cobaltate are not always satisfactory.
  • lithium cobaltate is made into fine particles and the particle size distribution and particle size are in a specific range, so that deterioration of charge / discharge characteristics can be suppressed by a homogeneous electrolytic reaction.
  • the output characteristics have not been improved only by adjusting the particle size of the particles.
  • an object of the present invention is to provide an electrode material that provides a lithium ion secondary battery having good output characteristics even when lithium cobalt oxide is used as a positive electrode active material, an electricity storage device including the electrode material, and an electrode material. It is to provide a manufacturing method.
  • the present invention provides an electrode material in which a lithium cobalt oxide is supported on a carbon material, and the electrode material has an electrode density in a range of 2.5 g / cc or less.
  • an electricity storage device including an electrode formed using this electrode material is also one embodiment of the present invention.
  • the manufacturing method of this invention includes the following processes. (1) A precursor supporting step of supporting a precursor of lithium cobalt oxide on a carbon material by applying shear stress and centrifugal force to a reaction liquid containing a material source of lithium cobalt oxide and a carbon material; (2) A heat treatment step in which a precursor of lithium cobalt oxide supported on the carbon material is subjected to heat treatment to obtain a lithium cobalt oxide supported on the carbon material and nanonized. An electrode material having an electrode density of 2.5 g / cc or less is manufactured by the above steps (1) and (2).
  • the heat treatment step is preferably performed in an atmosphere containing oxygen.
  • 3 is a flowchart showing a manufacturing process of an electrode material in which LiCoO 2 is supported on a carbon material (KB) according to Example 1; Is a SEM ( ⁇ 10k) image of the electrode material was supported LiCoO 2 carbon material (KB) in Example 3. Is a SEM ( ⁇ 50k) image of the electrode material was supported LiCoO 2 carbon material (KB) in Example 3.
  • Electrode material The lithium cobalt oxide contained in the electrode material according to the present invention is a material capable of occluding and releasing lithium, and examples include LiCo 2 and LiCo1-yNiyO 2 (0.1 ⁇ y ⁇ 0.5). . These lithium cobalt oxides may contain some subcomponent elements (transition metals such as Ti, Nb, Sn, and Mg).
  • any carbon material having conductivity can be used without any particular limitation.
  • Examples include carbon black such as ketjen black (hereinafter referred to as KB), acetylene black and channel black, fullerene, carbon nanotube, carbon nanofiber (hereinafter referred to as CNF), amorphous carbon, carbon fiber, natural graphite, artificial graphite, Examples thereof include graphitized ketjen black, activated carbon, and mesoporous carbon.
  • vapor grown carbon fiber can be used.
  • the carbon material may be used alone or in combination of two or more.
  • a fibrous carbon material and a spherical carbon material are used in combination in order to improve output characteristics. It is preferable to do. It is preferable that at least a part of the carbon material is a carbon nanotube or a carbon nanofiber. This is because a highly conductive electrode material can be obtained.
  • the particle diameter of the carbon material is preferably in the range of 10 nm to 300 nm, more preferably in the range of 10 to 100 nm, and particularly preferably in the range of 10 to 50 nm.
  • the lithium cobalt oxide is supported on the carbon material as nanoparticles.
  • the nanoparticle has nano-level primary particles. Nanoparticles are those having a diameter of 5 to 500 nm or less in a lump such as a circle, ellipse or polygon.
  • the lithium cobalt oxide has a lithium cobalt oxide primary particle size of 110 to 500 nm (large particles) and a particle size of less than 5 to 110 nm.
  • Lithium cobalt oxide (small particles) is supported on a carbon material. Small particles may be supported on the surface of large particles.
  • the size of the lithium cobalt oxide nanoparticles of the present invention is 5 to 500 nm, and large particles and small particles are distributed and mixed therein. That is, the particle size distribution is polydispersed. Large particles are distributed so that the particle size distribution has a maximum value in the range of 110 to 500 nm, and small particles have a maximum particle size distribution in the range of 5 to 110 nm. Distributed.
  • the lithium cobalt oxide having different particle size distribution is supported on the carbon material as the primary particles of the lithium cobalt oxide, whereby the density of the electrode layer can be increased and the capacity can be increased.
  • the particle size of the primary particles is a value obtained by observing the electrode material with an SEM, selecting randomly large particles and small particles, and measuring the particle size. In Examples described later, the particle diameter of the nanoparticles was determined by this method.
  • lithium cobalt oxide is contained in an amount of 60 wt% or more in the electrode material, and the carbon material is contained in 40 wt% or less.
  • a high energy density electrode material can be obtained by blending lithium cobalt oxide in a proportion of 70 wt% or more and a carbon material in a proportion of 30 wt% or less.
  • the carbon material a spherical carbon material and a fibrous carbon material may be mixed.
  • the capacity can be improved by mixing spherical KB and fibrous CNF.
  • This electrode material is obtained as a powder, and the electrode material powder is kneaded with a predetermined solvent and a binder to form an electrode that stores electrical energy.
  • This electrode can be used for an electrochemical capacitor or a battery using an electrolytic solution containing lithium. That is, an electrode made of this secondary battery or capacitor electrode material can occlude and desorb lithium ions and operates as a positive electrode.
  • An example of a manufacturing process of an electrode material in which lithium cobalt oxide is supported on the carbon material of the present embodiment includes the following steps a) to c).
  • a heat treatment step including a step of heat-treating a precursor of lithium cobalt oxide supported on the carbon material to obtain a nano cobaltized lithium cobalt oxide supported on the carbon material.
  • supported lithium cobalt oxide on the obtained carbon material is the range of 2.5 g / cc or less.
  • (A) Adjustment Step In the adjustment step, at least one compound containing a metal that is a material source of lithium cobalt oxide (hereinafter referred to as “material source”) and a carbon material are added to a solvent, and a material source is added. Is dissolved in a solvent to obtain a reaction solution.
  • material source a material source of lithium cobalt oxide
  • any liquid that does not adversely affect the reaction can be used without particular limitation, and water, methanol, ethanol, isopropyl alcohol, and the like can be preferably used. Two or more solvents may be mixed and used.
  • Examples of the compound containing a metal which is a material source of lithium cobalt oxide include the following.
  • Lithium source Lithium hydroxide (LiOH.H 2 O) can be used.
  • lithium compounds such as lithium acetate, lithium carbonate, and lithium nitrate can be used.
  • Cobalt source Cobalt acetate (Co (CH 3 COO) 2 .4H 2 O) can be used.
  • cobalt compounds such as cobalt nitrate, cobalt sulfate, and cobalt chloride can also be used.
  • the precursor supporting step is a step of supporting a precursor of lithium cobalt oxide on the surface of the carbon material.
  • the reactor shown in FIG. 2 is swirled to apply a shear stress and a centrifugal force to the reaction solution (hereinafter referred to as “UC treatment”). Load the source.
  • the reaction vessel comprises an outer cylinder 1 having a cough plate 1-2 at an opening and an inner cylinder 2 having a through hole 2-1 and turning.
  • the reaction solution is introduced into the inner cylinder 2 of the reactor, and the inner cylinder 2 is turned so that the cobalt source and the carbon material, which are the reactants in the inner cylinder 2 by the centrifugal force, pass through the through-hole 2-1 of the inner cylinder. And moves to the inner wall 1-3 of the outer cylinder.
  • the reaction product collides with the inner wall 1-3 of the outer cylinder by the centrifugal force of the inner cylinder 2, and forms a thin film and slides up to the upper part of the inner wall 1-3.
  • both the shear stress between the inner wall 1-3 and the centrifugal force from the inner cylinder are simultaneously applied to the reactant, and a large mechanical energy is applied to the thin-film reactant.
  • This mechanical energy seems to be converted into chemical energy required for the reaction, so-called activation energy, but the reaction proceeds in a short time.
  • shear stress and centrifugal force are applied to the cobalt source and the carbon material to adsorb at least a part of the cobalt source to the carbon material.
  • the thickness of the thin film is 5 mm or less, preferably 2.5 mm or less, more preferably 1.0 mm or less.
  • the thickness of the thin film can be set according to the width of the dam plate and the amount of the reaction solution.
  • the centrifugal force required to produce this thin film is 1500 N (kgms -2) or more, preferably 60000N (kgms -2) or more, more preferably 270000N (kgms -2) or more.
  • a lithium source is further added to the reaction solution, and a second UC treatment is performed to cause a mechanochemical reaction to generate a precursor of lithium cobalt oxide on the carbon material.
  • alkali metal hydroxide lithium hydroxide, sodium hydroxide, etc.
  • the cobalt source reacts to become a hydroxide, and the loading efficiency on the carbon material is improved.
  • the lithium source can be contained in the reaction solution and subjected to the UC treatment.
  • the lithium source may be mixed during the heat treatment step described later.
  • the mixing process of the lithium source can be simultaneously performed by the UC process, it is preferable to mix together at the precursor supporting step.
  • the heat treatment step is a step of synthesizing and crystallizing a precursor of lithium cobalt oxide supported on a carbon material.
  • a hydrothermal synthesis method which is a method for synthesizing a compound and growing a crystal in the presence of high-pressure steam, can be used.
  • This hydrothermal synthesis is carried out in saturated steam by charging the aqueous raw material solution into an autoclave, heating it under pressure.
  • the heating temperature is usually 110 to 300 ° C. although it depends on the type of metal salt used as a raw material. Pressurization is simultaneously performed by heating in a closed container.
  • the internal pressure of the autoclave is generally determined by the temperature, but it may be positively pressurized and is preferably about 1.1 to 84.8 atm.
  • a lithium cobalt oxide precursor is synthesized and crystallized.
  • a carbon material oxidizes and disappears when the temperature exceeds 300 ° C. in an atmosphere containing oxygen.
  • the precursor of lithium cobalt oxide can be synthesized and crystallized at 300 ° C. or lower, and thus can be performed in an atmosphere containing oxygen. This is particularly effective in lithium cobalt oxide that requires oxygen in the heat treatment step.
  • it is possible to synthesize and crystallize a lithium cobalt oxide precursor at a relatively low temperature of 300 ° C. or lower even a nano-level small precursor dispersed and supported on a carbon material by UC treatment can be crystallized. Thus, lithium cobalt oxide dispersed and supported on a carbon material as nanoparticles can be generated.
  • the carbon material does not disappear at a heating temperature of 110 to 300 ° C., which is a heating temperature in the hydrothermal synthesis method, and lithium cobalt oxide is dispersed and supported as nanoparticles on the surface of the carbon material.
  • an organic solvent such as alcohols (ethanol, methanol, isopropyl alcohol, etc.) or a mixed solution of these organic solvents and water is used in addition to water as a solvent to be charged into the autoclave. It can also be used.
  • the heat treatment step is performed at a relatively low temperature of 110 to 300 ° C. Therefore, even a lithium cobalt oxide precursor made of a thermodynamically unstable material can be crystallized. Similarly, a crystal having a small particle size that is more susceptible to heat than one having a large particle size can be crystallized at a low temperature.
  • the electrode material produced by this manufacturing method maintains lithium cobalt oxide as nanoparticles.
  • a battery using the electrode material as an electrode material for a lithium secondary battery or an electrical storage device such as an electrochemical capacitor achieves higher input / output and higher capacity.
  • the electrode material according to the present invention is an electrode material in which lithium cobalt oxide is supported on a carbon material, and the electrode density is increased to a range of 2.5 g / cc or less. Good results are obtained in energy density and output characteristics. In general, it is thought that increasing the electrode density increases the electrode capacity, resulting in an increase in energy density and output characteristics. However, an electrode material in which a lithium cobalt oxide is supported on a carbon material is used to increase the electrode capacity. Even if an electrode having a high density was prepared, the energy density and the rate characteristics were not improved, but it deteriorated.
  • the electrode material in which fine nano-level lithium cobalt oxide is supported on the carbon material as in the present invention has a high energy density by making the electrode density within a specific density range, and the output characteristics Gives good results. If the electrode density is less than 1.2 g / cc, the electrode density is not sufficient, and good energy density and output characteristics are not obtained. Therefore, the range of the electrode density of the present invention is preferably 1.2 g / cc or more and 2.5 g / cc or less.
  • electrode density refers to an electrode material in which lithium cobalt oxide is supported on a carbon material, N-methylpyrrolidone as a specific solvent, and polyvinylidene fluoride as a binder.
  • a slurry in which the solvent was 50 and the binder was formed at a weight ratio of 5 was applied onto an aluminum foil and dried to create an electrode layer on the aluminum foil, and the mass per unit volume of the electrode layer And Specifically, in the thickness region (volume) of the electrode layer at 1 cm 2 of the electrode layer, a value obtained by dividing the weight of the solid content including the electrode material by the volume.
  • the solid content includes polyvinylidene fluoride.
  • the electrode density of the electrode material according to the present invention is a change in the particle diameter of lithium cobalt oxide and the blending ratio of lithium cobalt oxide and carbon material (wt%), treatment conditions for hydrothermal synthesis, Other electrode materials obtained can be adjusted by performing ball milling or not.
  • the electrode material of this invention is suitable for the positive electrode of a lithium ion secondary battery. Accordingly, the present invention also provides a lithium ion secondary comprising a positive electrode having an electrode layer containing the electrode material of the present invention, a negative electrode, and a separator holding a non-aqueous electrolyte disposed between the negative electrode and the positive electrode. Provide batteries.
  • An electrode layer for the positive electrode is obtained by dispersing an electrode material in which a lithium cobalt oxide is supported on the carbon material of the present invention in a solvent (N-methylpyrrolidone, isopropyl alcohol, etc.) in which a binder is dissolved, if necessary.
  • the obtained dispersion can be prepared by coating on a current collector by a doctor blade method or the like and drying. Further, the obtained dispersion may be formed into a predetermined shape and may be pressure-bonded on the current collector.
  • a mixed material layer can also be formed by using a mixed solvent in which a metal oxide or a carbon material is further mixed and dispersed in the electrode material and binder-containing solvent of the present invention.
  • a conductive material such as platinum, gold, nickel, aluminum, titanium, steel, or carbon can be used.
  • shape of the current collector any shape such as a film shape, a foil shape, a plate shape, a net shape, an expanded metal shape, and a cylindrical shape can be adopted.
  • binder known binders such as polytetrafluoroethylene, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, polyvinyl fluoride, and carboxymethyl cellulose are used.
  • the binder content is preferably 1 to 30% by mass with respect to the total amount of the mixed material. If it is 1% by mass or less, the strength of the electrode layer is not sufficient, and if it is 30% by mass or more, the discharge capacity of the negative electrode is reduced and internal resistance becomes excessive.
  • a negative electrode provided with an electrode layer containing a known negative electrode active material can be used without any particular limitation.
  • the negative electrode active material include Fe 2 O 3 , MnO, MnO 2 , Mn 2 O 3 , Mn 3 O 4 , CoO, Co 3 O 4 , NiO, Ni 2 O 3 , TiO, TiO 2 , SnO, SnO 2 , oxides such as SiO 2 , RuO 2 , WO, WO 2 , ZnO, metals such as Sn, Si, Al, Zn, composite oxides such as LiVO 2 , Li 3 VO 4 , Li 4 Ti 5 O 12 , Examples thereof include nitrides such as Li 2.6 Co 0.4 N, Ge 3 N 4 , Zn 3 N 2 , and Cu 3 N.
  • the electrode layer for the negative electrode is dispersed on the current collector by the doctor blade method or the like by dispersing the negative electrode electrode material and the conductive agent in a solvent in which a binder is dissolved as necessary. It can be created by drying. Further, the obtained dispersion may be formed into a predetermined shape and may be pressure-bonded on the current collector.
  • the description of the current collector and binder for the positive electrode also applies to the negative electrode.
  • the conductive agent carbon powder such as carbon black, natural graphite, and artificial graphite can be used.
  • a polyolefin fiber nonwoven fabric or a glass fiber nonwoven fabric is preferably used.
  • an electrolytic solution in which an electrolyte is dissolved in a non-aqueous solvent is used, and a known non-aqueous electrolytic solution can be used without any particular limitation.
  • Examples of the solvent for the non-aqueous electrolyte include electrochemically stable ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, sulfolane, 3-methyl sulfolane, ⁇ -butyrolactone, acetonitrile, and dimethoxyethane, N-methyl-2-pyrrolidone, dimethylformamide or a mixture thereof can be preferably used.
  • a salt that generates lithium ions when dissolved in an organic electrolytic solution can be used without any particular limitation.
  • LiPF 6, LiBF 4, LiClO 4, LiN (CF 3 SO 2) 2, LiCF 3 SO 3, LiC (SO 2 CF 3) 3, LiN (SO 2 C 2 F 5) 2, LiAsF 6, LiSbF 6 Or a mixture thereof can be preferably used.
  • a solute of the nonaqueous electrolytic solution a quaternary ammonium salt or a quaternary phosphonium salt having a quaternary ammonium cation or a quaternary phosphonium cation can be used in addition to a salt that generates lithium ions.
  • Example 1 As shown in FIG. 3, first, a reaction liquid prepared by mixing ketjen black (KB), Co (CH 3 COO) 2 .4H 2 O, which is a cobalt source as a material source, and distilled water is prepared (adjusted). Then, the reaction solution was subjected to UC treatment for 5 minutes at a rotational speed of 50 m / s. The reaction solution that had been subjected to the UC treatment was added with LiHO.H 2 O as a lithium source, and further subjected to a UC treatment for 5 minutes at a rotational speed of 50 m / s. In this UC process, a centrifugal force of 66000 N (kgms ⁇ 2 ) is applied.
  • the first and second UC processes correspond to a precursor supporting process in which a LiCoO 2 precursor by UC process is supported on a carbon material.
  • the obtained solution is filtered and dried, further rapidly heated to 250 ° C. in an oxidizing atmosphere such as the air, and kept for 1 hour to perform a preheating treatment.
  • H 2 O the precursor prepared by the pre-heating treatment, and H 2 O 2 are added to the autoclave, hydrothermal synthesis is performed, and the mixture is held at 250 ° C. for 6 hours, and LiCoO 2 is supported on the KB.
  • An electrode material was obtained. The pressure at this time is 39.2 atmospheres. This hydrothermal synthesis corresponds to the heat treatment process. At this time, adjustment is made so that LiCoO 2 in the electrode material is 80 wt% and KB is 20 wt%.
  • an electrode material in which LiCoO 2 is supported on the obtained KB is used together with polyvinylidene fluoride (PVDF) as a binder and N-methylpyrrolidone (NMP) as a solvent (LiCoO 2 / KB / PVDF / NMP). 80: 20: 5: 50 / wt%) was dispersed to prepare an electrode slurry. This electrode slurry was put into a SUS mesh welded on a SUS plate and dried to form an electrode layer having an electrode thickness of 10 ⁇ m. E. It was.
  • PVDF polyvinylidene fluoride
  • NMP N-methylpyrrolidone
  • a value obtained by dividing the weight of the solid content in the thickness region (volume) at 1 cm 3 of this electrode layer by the volume was measured and shown as an electrode density in Table 1 (the electrode density shown in the following examples and comparative examples is the method) ).
  • a separator and a counter electrode C. are formed on the electrode layer.
  • E. In addition, a Li foil was placed as a reference electrode, and a 1M LiPF6 ethylene carbonate / diethyl carbonate 1: 1 solution was infiltrated as an electrolyte solution to obtain a battery cell.
  • Example 2 to Example 5 In Examples 2 to 5, in the electrode material in which LiCoO 2 was supported on the KB prepared in Example 1, the treatment temperature and treatment time of hydrothermal synthesis were changed, and the electrode materials having the electrode densities shown in Table 1 were obtained. Was made. Using the electrode material, batteries of Examples 2 to 5 were produced. In Examples 2 to 5, adjustment is made so that LiCoO 2 in the electrode material is 80 wt% and KB is 20 wt%.
  • Comparative Example 1 In order to further increase the electrode density, the electrode material in which LiCoO 2 was supported on KB prepared in Example 1 was examined by changing the treatment temperature and treatment time of hydrothermal synthesis. It was difficult to produce an electrode material having an electrode density of / cc. Instead, the electrode material in which LiCoO 2 was supported on the KB prepared in Example 1 was further ball milled to increase the electrode density, and the electrode material having an increased electrode density shown in Table 1 was obtained. It was. And the battery of the comparative example 1 was created using this electrode material. The battery of Comparative Example 1 was prepared by using the same method as in Example 1 except that the electrode material subjected to densification treatment was used for the electrode layer by a ball mill.
  • the rate characteristic indicates the maintenance rate (%) of the energy density of 10C with respect to the energy density of 0.1C.
  • the battery cell using the electrode material of Comparative Example 1 has a 10C compared to the battery cell using the electrode material of Examples 1 to 5 despite the high electrode density.
  • the energy density was remarkably small, and the rate characteristics were also low.
  • the battery cell using the electrode material of Example 1 has extremely good energy density and rate characteristics, and has an energy density exceeding 200 Wh / L even in Example 1 where the electrode density is low. It was.
  • FIG. 4 shows an SEM image ( ⁇ 10 k) of an electrode material in which LiCoO 2 is supported on a carbon material (KB) before electrode preparation in Example 3.
  • FIG. 5 further shows an SEM image ( ⁇ 50 k) of the electrode material in Example 3.
  • Example 3 fine nanoparticles can be seen. Further, in FIG. 5 was observed by increasing the magnification, when observing the electrode material of Example 3, a relatively particle size large LiCoO 2 particles (particle diameter 110 ⁇ 500 nm), relatively particle size small LiCoO 2 particles (Particle diameter 5 to less than 110 nm) is supported. Some of the LiCoO 2 particles having a relatively small particle diameter are supported on the surface of the LiCoO 2 particles having a large particle diameter. It can be seen that these LiCoO 2 particles are highly dispersed at the nano level.
  • Example 6 The conditions other than the ratio of the carbon material in the electrode material of Example 3 were the same, and CNF was mixed as a carbon material in addition to KB.
  • electrode materials were obtained by changing the blending ratio of LiCoO 2 and carbon materials (KB and CNF), and batteries of Examples 6 to 8 were made using these electrode materials.
  • the ratios of LiCoO 2 , KB, and CNF in the electrode materials of Examples 6 to 8 at this time are as shown in Table 2.
  • the batteries of Examples 6 to 8 were evaluated for energy density and rate characteristics at a 10 C rate, and the results are shown in Table 2.
  • the rate characteristic indicates the maintenance rate (%) of the energy density of 10C with respect to the energy density of 0.1C.
  • the batteries of Examples 6 to 8 all had an energy density at 10 C rate exceeding 200 Wh / L, and the rate characteristics had good values. Especially, the energy density of the battery cells of Example 7 and Example 8 in which 70% by weight or more of LiCoO 2 was blended was extremely good. Moreover, it became a result that the capacity

Abstract

Provided are: a method for producing an electrode material having improved output characteristics; and an electricity storage device which is provided with the electrode material. A method for producing an electrode material wherein a carbon material is loaded with lithium cobalt oxide, said method comprising: a preparation step wherein a reaction liquid containing the carbon material and material sources of lithium cobalt oxide is prepared; a precursor loading step wherein the carbon material is loaded with a precursor of lithium cobalt oxide by applying a shear stress and a centrifugal force to the reaction liquid; and a heat treatment step wherein the carbon material loaded with the precursor is subjected to a heat treatment, thereby obtaining nano-sized lithium cobalt oxide. The output characteristics are improved by setting the electrode density of the thus-obtained electrode material to 2.5 g/cc or less.

Description

電極材料、該電極材料を備えた蓄電デバイス及び電極材料の製造方法Electrode material, electric storage device provided with the electrode material, and method for producing electrode material
　本発明は、炭素材料に電極活物質を担持させた電極材料、該電極材料の製造方法および該電極材料を備えた蓄電デバイスに関する。本発明では、電極活物質として、リチウムコバルト酸化物を使用する。 The present invention relates to an electrode material in which an electrode active material is supported on a carbon material, a method for producing the electrode material, and an electricity storage device including the electrode material. In the present invention, lithium cobalt oxide is used as the electrode active material.
　携帯電話やノート型パソコンなどの情報機器の電源として、エネルギー密度が高い非水系電解液を使用したリチウムイオン二次電池が広く使用されているが、これらの情報機器の高性能化や取扱う情報量の増大に伴う消費電力の増加に対応するために、リチウムイオン二次電池のエネルギー密度の向上が望まれている。また、石油消費量の低減、大気汚染の緩和、地球温暖化の原因となる二酸化炭素の排出量の低減などの観点から、ガソリン車やティーゼル車に代わる電気自動車やハイブリッド自動車などの低公害車に対する期待が高まっており、これらの低公害車のモーター駆動電源として、高いエネルギー密度を有する大型のリチウムイオン二次電池の開発が望まれている。 Lithium ion secondary batteries that use non-aqueous electrolytes with high energy density are widely used as the power source for information devices such as mobile phones and laptop computers. The performance of these information devices and the amount of information handled In order to cope with an increase in power consumption associated with an increase in the energy consumption, an improvement in the energy density of the lithium ion secondary battery is desired. In addition, from the viewpoints of reducing oil consumption, mitigating air pollution, and reducing emissions of carbon dioxide, which causes global warming, we are working on low-emission vehicles such as electric vehicles and hybrid vehicles that replace gasoline and teal vehicles. Expectations are increasing, and it is desired to develop a large lithium ion secondary battery having a high energy density as a motor drive power source for these low-pollution vehicles.
　現在の非水系電解液を使用したリチウムイオン二次電池としては、高いエネルギー密度を有するものとして、コバルト酸リチウム（ＬｉＣｏＯ２）を正極活物質として用いるものが期待され、実用化が進んでいる。例えば特許文献１には、正極活物質としてＬｉＣｏＯ２を用い、カーボンを負極として用いる二次電池が開示されている。また特許文献２には、レート特性などの充放電特性を改善するべく、コバルト酸リチウム粉を１～４０μｍの粒度分布、かつ平均粒径５～１５μｍなどの特定範囲としたリチウムイオン二次電池が開示されている。 As a lithium ion secondary battery using a current non-aqueous electrolyte, one using lithium cobalt oxide (LiCoO 2 ) as a positive electrode active material is expected as a battery having a high energy density, and its practical application is progressing. For example, Patent Document 1 discloses a secondary battery using LiCoO 2 as a positive electrode active material and carbon as a negative electrode. Patent Document 2 discloses a lithium ion secondary battery in which lithium cobaltate powder has a particle size distribution of 1 to 40 μm and a specific range such as an average particle size of 5 to 15 μm in order to improve charge / discharge characteristics such as rate characteristics. It is disclosed.
特開昭６３－１２１２６０号公報Japanese Unexamined Patent Publication No. Sho 63-121260 特開２００１－１８５１４２号公報JP 2001-185142 A
　しかしながら、上述のような正極活物質であるコバルト酸リチウムに関しては、未だコバルト酸リチウムの出力特性は必ずしも満足のいくものでは無い。特許文献２のように、コバルト酸リチウムを微粒子化し、粒度分布や粒径を特定の範囲とすることで、均質な電解反応によって充放電特性の悪化を抑制することはできるが、コバルト酸リチウム粉の粒径などの調整だけでは、出力特性は未だ改善できていない。 However, with respect to lithium cobaltate, which is a positive electrode active material as described above, the output characteristics of lithium cobaltate are not always satisfactory. As described in Patent Document 2, lithium cobaltate is made into fine particles and the particle size distribution and particle size are in a specific range, so that deterioration of charge / discharge characteristics can be suppressed by a homogeneous electrolytic reaction. The output characteristics have not been improved only by adjusting the particle size of the particles.
　そこで、本発明の目的は、正極活物質としてリチウムコバルト酸化物を用いた場合でも、良好な出力特性を有するリチウムイオン二次電池をもたらす電極材料、該電極材料を備えた蓄電デバイス及び電極材料の製造方法を提供することである。 Accordingly, an object of the present invention is to provide an electrode material that provides a lithium ion secondary battery having good output characteristics even when lithium cobalt oxide is used as a positive electrode active material, an electricity storage device including the electrode material, and an electrode material. It is to provide a manufacturing method.
　前記の目的を達成するため、本発明は、炭素材料にリチウムコバルト酸化物を担持させた電極材料であって、前記電極材料は、その電極密度が２．５ｇ／ｃｃ以下の範囲であることを特徴とする。 In order to achieve the above object, the present invention provides an electrode material in which a lithium cobalt oxide is supported on a carbon material, and the electrode material has an electrode density in a range of 2.5 g / cc or less. Features.
また、この電極材料を用いて形成された電極を備えた蓄電デバイスも本発明の一態様である。 Further, an electricity storage device including an electrode formed using this electrode material is also one embodiment of the present invention.
また、前記の目的を達成しうるため、本発明の製造方法は、以下の工程を含むものである。
（１）リチウムコバルト酸化物の材料源と炭素材料とを含有する反応液にずり応力と遠心力とを加えることにより、炭素材料にリチウムコバルト酸化物の前駆体を担持させる前駆体担持工程と、
（２）前記炭素材料に担持させたリチウムコバルト酸化物の前駆体に加熱処理を行い、炭素材料に担持されるとともにナノ化したリチウムコバルト酸化物を得る熱処理工程。
　以上の（１）（２）の工程により、電極密度が２．５ｇ／ｃｃ以下の電極材料を製造する。 Moreover, since the said objective can be achieved, the manufacturing method of this invention includes the following processes.
(1) A precursor supporting step of supporting a precursor of lithium cobalt oxide on a carbon material by applying shear stress and centrifugal force to a reaction liquid containing a material source of lithium cobalt oxide and a carbon material;
(2) A heat treatment step in which a precursor of lithium cobalt oxide supported on the carbon material is subjected to heat treatment to obtain a lithium cobalt oxide supported on the carbon material and nanonized.
An electrode material having an electrode density of 2.5 g / cc or less is manufactured by the above steps (1) and (2).
なお、前記熱処理工程は、酸素を含む雰囲気下で処理を行うことが好適である。 Note that the heat treatment step is preferably performed in an atmosphere containing oxygen.
　本発明によれば、炭素材料にリチウムコバルト酸化物を担持させた電極材料であって、その電極材料の電極密度を２．５ｇ／ｃｃ以下の範囲とすることにより、出力特性が良好な電極を形成できる。 According to the present invention, an electrode material in which lithium cobalt oxide is supported on a carbon material, and the electrode density of the electrode material is in a range of 2.5 g / cc or less, an electrode having good output characteristics is obtained. Can be formed.
本実施形態に係る炭素素材にリチウムコバルト酸化物とリチウムコバルト酸化物を担持した電極材料の製造工程を示すフローチャートである。It is a flowchart which shows the manufacturing process of the electrode material which carry | supported lithium cobalt oxide and lithium cobalt oxide in the carbon raw material which concerns on this embodiment. 材料源担持工程のための装置を示す構成図である。It is a block diagram which shows the apparatus for a material source support process. 実施例１に係る炭素材料（ＫＢ）にＬｉＣｏＯ2を担持させた電極材料の製造工程を示すフローチャートである。3 is a flowchart showing a manufacturing process of an electrode material in which LiCoO 2 is supported on a carbon material (KB) according to Example 1; 実施例３における炭素材料（ＫＢ）にＬｉＣｏＯ2を担持させた電極材料のＳＥＭ（×１０ｋ）像である。Is a SEM (× 10k) image of the electrode material was supported LiCoO 2 carbon material (KB) in Example 3. 実施例３における炭素材料（ＫＢ）にＬｉＣｏＯ2を担持させた電極材料のＳＥＭ（×５０ｋ）像である。Is a SEM (× 50k) image of the electrode material was supported LiCoO 2 carbon material (KB) in Example 3.
　以下、本発明を実施する形態について、説明する。なお、本発明は、以下に説明する実施形態に限定されるものでない。 Hereinafter, embodiments for carrying out the present invention will be described. In addition, this invention is not limited to embodiment described below.
（１）電極材料
　本発明に係る電極材料に含まれるリチウムコバルト酸化物は、リチウムの吸蔵放出できる材料であり、ＬｉＣｏ２やＬｉＣｏ１－ｙＮｉｙＯ２（０．１≦ｙ≦０．５）が挙げられる。なお、これらのリチウムコバルト酸化物には若干の副成分元素（Ｔｉ、Ｎｂ、Ｓｎ及びＭｇなどの遷移金属など）が含まれていても良い。 (1) Electrode material The lithium cobalt oxide contained in the electrode material according to the present invention is a material capable of occluding and releasing lithium, and examples include LiCo 2 and LiCo1-yNiyO 2 (0.1 ≦ y ≦ 0.5). . These lithium cobalt oxides may contain some subcomponent elements (transition metals such as Ti, Nb, Sn, and Mg).
　電極材料に含まれる炭素材料としては、導電性を有している炭素材料であれば特に限定なく使用することができる。例としては、ケッチェンブラック（以下、ＫＢ）、アセチレンブラック、チャネルブラックなどのカーボンブラック、フラーレン、カーボンナノチューブ、カーボンナノファイバ（以下、ＣＮＦ）、無定形炭素、炭素繊維、天然黒鉛、人造黒鉛、黒鉛化ケッチェンブラック、活性炭、メソポーラス炭素などを挙げることができる。また、気相法炭素繊維を使用することもできる。これらの炭素材料が繊維構造を有する場合は（例えば、カーボンナノチューブ、カーボンナノファイバや気相成長カーボンファイバ）、繊維状の分散及び均質化を目的として超高圧分散処理を施したものを使用しても良い。また、炭素材料は、単独で使用しても良く、２種以上を混合して使用しても良く、特には出力特性が向上させるため繊維状の炭素材料と球状の炭素材料を併用して使用することが好適である。炭素材料の少なくとも一部がカーボンナノチューブ又はカーボンナノファイバであるのが好ましい。導電性の高い電極材料が得られるからである。炭素材料の粒子径は、１０ｎｍ～３００ｎｍの範囲であるのが好ましく、１０～１００ｎｍの範囲であるのがより好ましく、１０～５０ｎｍの範囲であるのが特に好ましい。 As the carbon material included in the electrode material, any carbon material having conductivity can be used without any particular limitation. Examples include carbon black such as ketjen black (hereinafter referred to as KB), acetylene black and channel black, fullerene, carbon nanotube, carbon nanofiber (hereinafter referred to as CNF), amorphous carbon, carbon fiber, natural graphite, artificial graphite, Examples thereof include graphitized ketjen black, activated carbon, and mesoporous carbon. Also, vapor grown carbon fiber can be used. When these carbon materials have a fiber structure (for example, carbon nanotubes, carbon nanofibers or vapor-grown carbon fibers), use those that have been subjected to ultra-high pressure dispersion treatment for the purpose of fiber dispersion and homogenization. Also good. In addition, the carbon material may be used alone or in combination of two or more. In particular, a fibrous carbon material and a spherical carbon material are used in combination in order to improve output characteristics. It is preferable to do. It is preferable that at least a part of the carbon material is a carbon nanotube or a carbon nanofiber. This is because a highly conductive electrode material can be obtained. The particle diameter of the carbon material is preferably in the range of 10 nm to 300 nm, more preferably in the range of 10 to 100 nm, and particularly preferably in the range of 10 to 50 nm.
　リチウムコバルト酸化物は、ナノ粒子として炭素材料に担持されている。ここでナノ粒子とは、ナノレベルの一次粒子を有するものである。そして、ナノ粒子とは、その径が、円形や楕円形や多角形等の塊においてはその大きさが５～５００ｎｍ以下をいう。また、リチウムコバルト酸化物は、電極材料の表面をＳＥＭで観察すると、リチウムコバルト酸化物の一次粒子の粒子径が１１０～５００ｎｍのリチウムコバルト酸化物（大きい粒子）、及び粒子径が５～１１０ｎｍ未満のリチウムコバルト酸化物（小さい粒子）が炭素材料に担持されている。なお、小さい粒子は、大きい粒子の表面に担持されていてもよい。つまり、本発明のリチウムコバルト酸化物のナノ粒子の大きさは、５～５００ｎｍであり、この中に、大きい粒子と小さい粒子とが分布して混在している。つまり、粒径子の分布は、多分散となる。大きい粒子は、粒子径が１１０～５００ｎｍの範囲での粒度分布の値が極大となるように分布し、小さな粒子は、粒子径が５～１１０ｎｍの範囲での粒度分布の値が極大となるように分布する。このようにリチウムコバルト酸化物の一次粒子として、異なる粒子径分布のリチウムコバルト酸化物が炭素材料に担持されることで、電極層として密度を高めることができ、高容量化が得られる。なお、一次粒子の粒子径は、電極材料をＳＥＭにて観察し、その中から無作為に大きい粒子、小さい粒子を選定し、その粒子径を測定した値である。後述の実施例では、この方法によりナノ粒子の粒子径を求めた。 The lithium cobalt oxide is supported on the carbon material as nanoparticles. Here, the nanoparticle has nano-level primary particles. Nanoparticles are those having a diameter of 5 to 500 nm or less in a lump such as a circle, ellipse or polygon. In addition, when the surface of the electrode material is observed with an SEM, the lithium cobalt oxide has a lithium cobalt oxide primary particle size of 110 to 500 nm (large particles) and a particle size of less than 5 to 110 nm. Lithium cobalt oxide (small particles) is supported on a carbon material. Small particles may be supported on the surface of large particles. That is, the size of the lithium cobalt oxide nanoparticles of the present invention is 5 to 500 nm, and large particles and small particles are distributed and mixed therein. That is, the particle size distribution is polydispersed. Large particles are distributed so that the particle size distribution has a maximum value in the range of 110 to 500 nm, and small particles have a maximum particle size distribution in the range of 5 to 110 nm. Distributed. As described above, the lithium cobalt oxide having different particle size distribution is supported on the carbon material as the primary particles of the lithium cobalt oxide, whereby the density of the electrode layer can be increased and the capacity can be increased. The particle size of the primary particles is a value obtained by observing the electrode material with an SEM, selecting randomly large particles and small particles, and measuring the particle size. In Examples described later, the particle diameter of the nanoparticles was determined by this method.
　本実施形態の電極材料においては、リチウムコバルト酸化物は、電極材料中の６０ｗｔ％以上含有される共に、炭素材料は、４０ｗｔ％以下含有される。特に、リチウムコバルト酸化物を７０ｗｔ％以上とし、炭素材料を３０ｗｔ％以下の割合で配合することで、高いエネルギー密度の電極材料が得られる。さらに、炭素材料としては、球状の炭素材料と繊維状の炭素材料を混合させても良い。例えば、球状であるＫＢと繊維状のＣＮＦを混合させることでその容量が向上する。 In the electrode material of the present embodiment, lithium cobalt oxide is contained in an amount of 60 wt% or more in the electrode material, and the carbon material is contained in 40 wt% or less. In particular, a high energy density electrode material can be obtained by blending lithium cobalt oxide in a proportion of 70 wt% or more and a carbon material in a proportion of 30 wt% or less. Furthermore, as the carbon material, a spherical carbon material and a fibrous carbon material may be mixed. For example, the capacity can be improved by mixing spherical KB and fibrous CNF.
　この電極材料は、粉末として得られ、電極材料の粉末を所定の溶媒とバインダとで混錬して成型することで、電気エネルギーを貯蔵する電極となる。この電極は、リチウムを含有する電解液を用いる電気化学キャパシタや電池に用いることができる。すなわち、この二次電池やキャパシタ用電極材料により作成された電極は、リチウムイオンの吸蔵、脱着を行うことができ、正極として作動する。 This electrode material is obtained as a powder, and the electrode material powder is kneaded with a predetermined solvent and a binder to form an electrode that stores electrical energy. This electrode can be used for an electrochemical capacitor or a battery using an electrolytic solution containing lithium. That is, an electrode made of this secondary battery or capacitor electrode material can occlude and desorb lithium ions and operates as a positive electrode.
（２）製造方法
　本実施形態の炭素材料にリチウムコバルト酸化物を担持させた電極材料の製造工程の一例は、次のａ）～ｃ）の工程を備える。
　ａ）リチウムコバルト酸化物の材料源となる金属を含む少なくとも一種の化合物を溶解させた溶液に炭素材料を添加した反応液を、旋回可能な反応器内に導入する調製工程。
　ｂ）上記反応器を旋回させて上記反応液にずり応力と遠心力とを加えることにより、上記炭素材料にリチウムコバルト酸化物の前駆体を担持させる担持工程。
　ｃ）前記炭素材料に担持させたリチウムコバルト酸化物の前駆体に加熱処理を行い、炭素材料に担持されるとともにナノ化したリチウムコバルト酸化物を得る工程を含む熱処理工程。
　以上のａ）～ｃ）の工程を経ることでリチウムコバルト酸化物が炭素材料に担持されることになる。そして、得られた炭素材料にリチウムコバルト酸化物を担持させた電極材料の電極密度は、２．５ｇ／ｃｃ以下の範囲である。 (2) Manufacturing Method An example of a manufacturing process of an electrode material in which lithium cobalt oxide is supported on the carbon material of the present embodiment includes the following steps a) to c).
a) A preparation step of introducing a reaction solution in which a carbon material is added to a solution in which at least one compound containing a metal serving as a material source of lithium cobalt oxide is dissolved into a swirlable reactor.
b) A supporting step in which a lithium cobalt oxide precursor is supported on the carbon material by rotating the reactor and applying shear stress and centrifugal force to the reaction solution.
c) A heat treatment step including a step of heat-treating a precursor of lithium cobalt oxide supported on the carbon material to obtain a nano cobaltized lithium cobalt oxide supported on the carbon material.
Through the steps a) to c), lithium cobalt oxide is supported on the carbon material. And the electrode density of the electrode material which carry | supported lithium cobalt oxide on the obtained carbon material is the range of 2.5 g / cc or less.
　（ａ）調整工程
　調整工程では、溶媒に、リチウムコバルト酸化物の材料源である金属を含む化合物（以下、「材料源」という。）の少なくとも１種と、炭素材料とを添加し、材料源を溶媒に溶解させることによって、反応液を得ている。 (A) Adjustment Step In the adjustment step, at least one compound containing a metal that is a material source of lithium cobalt oxide (hereinafter referred to as “material source”) and a carbon material are added to a solvent, and a material source is added. Is dissolved in a solvent to obtain a reaction solution.
　溶媒としては、反応に悪影響を及ぼさない液であれば特に限定なく使用することができ、水、メタノール、エタノール、イソプロピルアルコールなどを好適に使用することができる。２種以上の溶媒を混合して使用しても良い。 As the solvent, any liquid that does not adversely affect the reaction can be used without particular limitation, and water, methanol, ethanol, isopropyl alcohol, and the like can be preferably used. Two or more solvents may be mixed and used.
　リチウムコバルト酸化物の材料源である金属を含む化合物は次のものが例示できる。
（リチウム源）
　水酸化リチウム（ＬｉＯＨ・Ｈ２Ｏ）を用いることができる。水酸化リチウム以外のリチウム源としては、酢酸リチウム、炭酸リチウム、硝酸リチウムなどのリチウム化合物を利用することができる。
（コバルト源）
　酢酸コバルト（Ｃｏ（ＣＨ３ＣＯＯ）２・４Ｈ２Ｏ）を用いることができる。酢酸コバルト以外にも、硝酸コバルト、硫酸コバルト、塩化コバルトなどのコバルト化合物も使用することもできる。 Examples of the compound containing a metal which is a material source of lithium cobalt oxide include the following.
(Lithium source)
Lithium hydroxide (LiOH.H 2 O) can be used. As a lithium source other than lithium hydroxide, lithium compounds such as lithium acetate, lithium carbonate, and lithium nitrate can be used.
(Cobalt source)
Cobalt acetate (Co (CH 3 COO) 2 .4H 2 O) can be used. Besides cobalt acetate, cobalt compounds such as cobalt nitrate, cobalt sulfate, and cobalt chloride can also be used.
　（ｂ）前駆体担持工程
前駆体担持工程は、炭素材料の表面にリチウムコバルト酸化物の前駆体を担持させる行程である。前駆体を炭素材料に担持させる方法としては、図２示す反応器を旋回させて反応液にずり応力と遠心力とを加える（以下、「ＵＣ処理」という。）ことにより、炭素材料上に材料源を担持させる。 (B) Precursor supporting step The precursor supporting step is a step of supporting a precursor of lithium cobalt oxide on the surface of the carbon material. As a method for supporting the precursor on the carbon material, the reactor shown in FIG. 2 is swirled to apply a shear stress and a centrifugal force to the reaction solution (hereinafter referred to as “UC treatment”). Load the source.
　図２に示すように、反応容器は、開口部にせき板１－２を有する外筒１と、貫通孔２－１を有し旋回する内筒２からなる。この反応器の内筒２内部に反応液を投入し、内筒２を旋回することによってその遠心力で内筒２内部の反応物となるコバルト源及び炭素材料が内筒の貫通孔２－１を通って外筒の内壁１－３に移動する。この時反応物は内筒２の遠心力によって外筒の内壁１－３に衝突し、薄膜状となって内壁１－３の上部へずり上がる。この状態では反応物には内壁１－３との間のずり応力と内筒からの遠心力の双方が同時に加わり、薄膜状の反応物に大きな機械的エネルギーが加わることになる。この機械的なエネルギーが反応に必要な化学エネルギー、いわゆる活性化エネルギーに転化するものと思われるが、短時間で反応が進行する。このようにコバルト源と炭素材料にずり応力と遠心力とを加え、コバルト源の少なくとも一部を炭素材料に吸着させる。 As shown in FIG. 2, the reaction vessel comprises an outer cylinder 1 having a cough plate 1-2 at an opening and an inner cylinder 2 having a through hole 2-1 and turning. The reaction solution is introduced into the inner cylinder 2 of the reactor, and the inner cylinder 2 is turned so that the cobalt source and the carbon material, which are the reactants in the inner cylinder 2 by the centrifugal force, pass through the through-hole 2-1 of the inner cylinder. And moves to the inner wall 1-3 of the outer cylinder. At this time, the reaction product collides with the inner wall 1-3 of the outer cylinder by the centrifugal force of the inner cylinder 2, and forms a thin film and slides up to the upper part of the inner wall 1-3. In this state, both the shear stress between the inner wall 1-3 and the centrifugal force from the inner cylinder are simultaneously applied to the reactant, and a large mechanical energy is applied to the thin-film reactant. This mechanical energy seems to be converted into chemical energy required for the reaction, so-called activation energy, but the reaction proceeds in a short time. In this way, shear stress and centrifugal force are applied to the cobalt source and the carbon material to adsorb at least a part of the cobalt source to the carbon material.
　この反応において、薄膜状であると反応物に加えられる機械的エネルギーは大きなものとなるため、薄膜の厚みは５ｍｍ以下、好ましくは２．５ｍｍ以下、さらに好ましくは１．０ｍｍ以下である。なお、薄膜の厚みはせき板の幅、反応液の量によって設定することができる。例えば、この薄膜を生成するために必要な遠心力は１５００Ｎ（ｋｇｍｓ－２）以上、好ましくは６００００Ｎ（ｋｇｍｓ－２）以上、さらに好ましくは２７００００Ｎ（ｋｇｍｓ－２）以上である。 In this reaction, since the mechanical energy applied to the reaction product is large when it is in the form of a thin film, the thickness of the thin film is 5 mm or less, preferably 2.5 mm or less, more preferably 1.0 mm or less. The thickness of the thin film can be set according to the width of the dam plate and the amount of the reaction solution. For example, the centrifugal force required to produce this thin film is 1500 N (kgms -2) or more, preferably 60000N (kgms -2) or more, more preferably 270000N (kgms -2) or more.
その後、反応液にさらにリチウム源を加え２回目のＵＣ処理を実施することで、メカノケミカル反応させ、炭素材料上でリチウムコバルト酸化物の前駆体を生成する。また、水にアルカリ金属の水酸化物（水酸化リチウム、水酸化ナトリウムなど）を添加し、反応液のｐＨを９～１１の範囲に調整してもよい。所定のｐＨとすることで、コバルト源が反応して水酸化物となるとともに炭素材料への担持効率が向上する。 Thereafter, a lithium source is further added to the reaction solution, and a second UC treatment is performed to cause a mechanochemical reaction to generate a precursor of lithium cobalt oxide on the carbon material. Alternatively, alkali metal hydroxide (lithium hydroxide, sodium hydroxide, etc.) may be added to water to adjust the pH of the reaction solution to a range of 9-11. By setting the pH to a predetermined value, the cobalt source reacts to become a hydroxide, and the loading efficiency on the carbon material is improved.
　なお、上述のとおりリチウム源はこの反応液中に含有させてＵＣ処理を行うこともできるが、さらに、後述する熱処理工程の際にリチウム源を混合するようにしてもよい。また、リチウム源は、後述する熱処理工程の際にのみ混合するようにしてもよい。但し、ＵＣ処理により同時にリチウム源の混合処理を実施できるため、当該前駆体担持工程の際に一緒に混合することが好適である。 Note that, as described above, the lithium source can be contained in the reaction solution and subjected to the UC treatment. However, the lithium source may be mixed during the heat treatment step described later. Moreover, you may make it mix a lithium source only in the case of the heat processing process mentioned later. However, since the mixing process of the lithium source can be simultaneously performed by the UC process, it is preferable to mix together at the precursor supporting step.
　なお、一段階のＵＣ処理によっても、炭素材料に担持させたリチウムコバルト酸化物の前駆体の生成は可能である。この場合は炭素材料、コバルト源及びリチウム源を含む反応液のｐＨを調整し（必要に応じてホモジナイザーなどで反応液を攪拌して材料源及び炭素材料を分散させる）、反応器の内筒の内部に投入して内筒を旋回して、これらを混合、分散すると共にずり応力と遠心力を加え化学反応を促進させる。反応終了と共に、炭素材料に担持させたリチウムコバルト酸化物の前駆体を得ることができる。 Note that it is possible to generate a lithium cobalt oxide precursor supported on a carbon material even by a one-step UC treatment. In this case, adjust the pH of the reaction solution containing the carbon material, cobalt source and lithium source (if necessary, stir the reaction solution with a homogenizer to disperse the material source and carbon material) It is put into the interior and the inner cylinder is swung to mix and disperse them, and to add a shear stress and centrifugal force to promote a chemical reaction. At the end of the reaction, a precursor of lithium cobalt oxide supported on a carbon material can be obtained.
　このように前駆体担持工程を経て、リチウムコバルト酸化物の材料源が含有された反応液にずり応力と遠心力が加えられることで、炭素材料に担持されたリチウムコバルト酸化物の前駆体を生成することができる。 In this way, through the precursor loading process, shear stress and centrifugal force are applied to the reaction solution containing the lithium cobalt oxide material source, thereby generating a lithium cobalt oxide precursor supported on the carbon material. can do.
　（ｃ）熱処理工程
　熱処理工程では、炭素材料に担持させたリチウムコバルト酸化物の前駆体を合成及び結晶化させる工程である。この前駆体を合成及び結晶化の方法としては、高圧の水蒸気の存在下で行われる化合物の合成及び結晶を成長させる方法である水熱合成法を利用することができる。 (C) Heat treatment step The heat treatment step is a step of synthesizing and crystallizing a precursor of lithium cobalt oxide supported on a carbon material. As a method for synthesizing and crystallizing this precursor, a hydrothermal synthesis method, which is a method for synthesizing a compound and growing a crystal in the presence of high-pressure steam, can be used.
　この水熱合成は原料水溶液をオートクレーブに装入し加圧下に加熱し、飽和水蒸気中にて行なう。加圧・加熱することにより常温常圧下では水に溶けにくい物質を溶解させ、反応速度を増大させて、結晶の成長を促進することができる。加熱温度は、原料となる金属塩の種類にもよるが通常は１１０～３００℃である。密閉容器中で加熱することにより加圧も同時に行なわれる。オートクレーブ内圧は一般には温度によって決まるが、積極的に加圧してもよく１．１～８４．８気圧程度が好ましい。 This hydrothermal synthesis is carried out in saturated steam by charging the aqueous raw material solution into an autoclave, heating it under pressure. By applying pressure and heating, a substance that is difficult to dissolve in water at normal temperature and pressure can be dissolved, the reaction rate can be increased, and crystal growth can be promoted. The heating temperature is usually 110 to 300 ° C. although it depends on the type of metal salt used as a raw material. Pressurization is simultaneously performed by heating in a closed container. The internal pressure of the autoclave is generally determined by the temperature, but it may be positively pressurized and is preferably about 1.1 to 84.8 atm.
　水熱合成では、リチウムコバルト酸化物の前駆体を合成及び結晶化させる。通常、炭素材料は、酸素を含む雰囲気中で、３００℃を超えると酸化し消失する。水熱合成では、３００℃以下で、リチウムコバルト酸化物の前駆体を合成及び結晶化させることが可能であるため、酸素を含む雰囲気下で行うことが可能となる。特に、熱処理工程で酸素を必要とするリチウムコバルト酸化物において有効である。また、３００℃以下という比較的低温でリチウムコバルト酸化物の前駆体を合成及び結晶化させることが可能であるため、ＵＣ処理にて炭素材料に分散担持させたナノレベルの小さな前駆体においても結晶を維持し、ナノ粒子として炭素材料に分散担持させたリチウムコバルト酸化物を生成できる。 In hydrothermal synthesis, a lithium cobalt oxide precursor is synthesized and crystallized. Usually, a carbon material oxidizes and disappears when the temperature exceeds 300 ° C. in an atmosphere containing oxygen. In the hydrothermal synthesis, the precursor of lithium cobalt oxide can be synthesized and crystallized at 300 ° C. or lower, and thus can be performed in an atmosphere containing oxygen. This is particularly effective in lithium cobalt oxide that requires oxygen in the heat treatment step. In addition, since it is possible to synthesize and crystallize a lithium cobalt oxide precursor at a relatively low temperature of 300 ° C. or lower, even a nano-level small precursor dispersed and supported on a carbon material by UC treatment can be crystallized. Thus, lithium cobalt oxide dispersed and supported on a carbon material as nanoparticles can be generated.
炭素材料は、水熱合成法での加熱温度である１１０～３００℃で消失しないものであり、この炭素材料の表面には、リチウムコバルト酸化物がナノ粒子として分散担持されている。なお、この水熱合成法においては、オートクレーブに投入する溶媒として水以外にも、例えばアルコール類（エタノール、メタノール、イソプロピルアルコール等）などの有機溶媒や、これらの有機溶媒と水との混合溶液を用いることもできる。 The carbon material does not disappear at a heating temperature of 110 to 300 ° C., which is a heating temperature in the hydrothermal synthesis method, and lithium cobalt oxide is dispersed and supported as nanoparticles on the surface of the carbon material. In this hydrothermal synthesis method, an organic solvent such as alcohols (ethanol, methanol, isopropyl alcohol, etc.) or a mixed solution of these organic solvents and water is used in addition to water as a solvent to be charged into the autoclave. It can also be used.
　この水熱合成法により生じる現象は以下のように考えられる。まず、本発明では、１１０～３００℃という比較的低温で熱処理工程が行われる。そのため、熱力学的に不安定な材料からなるリチウムコバルト酸化物の前駆体でも、結晶化させることができる。同様に、粒子径が大きいものよりも、熱の影響を受けやすい粒子径が小さい結晶も、低温で結晶化することができると思われる。 The phenomenon caused by this hydrothermal synthesis method is considered as follows. First, in the present invention, the heat treatment step is performed at a relatively low temperature of 110 to 300 ° C. Therefore, even a lithium cobalt oxide precursor made of a thermodynamically unstable material can be crystallized. Similarly, a crystal having a small particle size that is more susceptible to heat than one having a large particle size can be crystallized at a low temperature.
　すなわち、熱処理の際に高温反応を用いると、炭素材料が消失してしまい、ナノレベルのリチウムコバルト酸化物を担持した炭素材料を得ることができず、また不安定な結晶となっていた。しかしながら、この水熱合成法を用いることで、低温での合成を行っているため、熱による影響が少なく、炭素材料が消失せず、ＵＣ処理によってナノ化したリチウムコバルト酸化物を担持した炭素材料が得られる。 That is, if a high temperature reaction is used during the heat treatment, the carbon material disappears, and a carbon material carrying nano-level lithium cobalt oxide cannot be obtained, and the crystal is unstable. However, since this hydrothermal synthesis method is used for synthesis at low temperatures, the carbon material is less affected by heat, the carbon material does not disappear, and carries a lithium cobalt oxide that is nano-sized by UC treatment. Is obtained.
　そして、この製造方法により作成された電極材料は、リチウムコバルト酸化物がナノ粒子として維持されている。それにより当該電極材料をリチウム二次電池用電極材料として用いた電池や電気化学キャパシタなどの蓄電デバイスは、その高入出力化及び高容量化が達成されることとなる。 And the electrode material produced by this manufacturing method maintains lithium cobalt oxide as nanoparticles. As a result, a battery using the electrode material as an electrode material for a lithium secondary battery or an electrical storage device such as an electrochemical capacitor achieves higher input / output and higher capacity.
　（３）電極材料の電極密度
　本発明に係る電極材料は、炭素材料にリチウムコバルト酸化物を担持させた電極材料であり、その電極密度を２．５ｇ／ｃｃ以下の範囲とすることにより、高エネルギー密度と出力特性において良好な結果が得られる。通常電極密度を向上させることで、電極容量が増えそれに伴いエネルギー密度や出力特性も増加すると考えられるが、炭素材料にリチウムコバルト酸化物を担持させた電極材料においては、この電極材料を用いて高密度の電極を作成してもエネルギー密度及びレート特性が向上せず、逆に悪化してしまっていた。しかし、本発明のような炭素材料に微細であるナノレベルのリチウムコバルト酸化物を担持させた電極材料においては、電極密度を特定の密度の範囲とすることで高エネルギー密度を有し、出力特性が良好な結果となる。尚、電極密度が１．２ｇ／ｃｃ未満では、電極密度が十分でなく、良好なエネルギー密度、出力特性とならない。そのため、本発明の電極密度の範囲としては、１．２ｇ／ｃｃ以上、且つ２．５ｇ／ｃｃ以下の範囲が好ましい。 (3) Electrode Density of Electrode Material The electrode material according to the present invention is an electrode material in which lithium cobalt oxide is supported on a carbon material, and the electrode density is increased to a range of 2.5 g / cc or less. Good results are obtained in energy density and output characteristics. In general, it is thought that increasing the electrode density increases the electrode capacity, resulting in an increase in energy density and output characteristics. However, an electrode material in which a lithium cobalt oxide is supported on a carbon material is used to increase the electrode capacity. Even if an electrode having a high density was prepared, the energy density and the rate characteristics were not improved, but it deteriorated. However, in the electrode material in which fine nano-level lithium cobalt oxide is supported on the carbon material as in the present invention, it has a high energy density by making the electrode density within a specific density range, and the output characteristics Gives good results. If the electrode density is less than 1.2 g / cc, the electrode density is not sufficient, and good energy density and output characteristics are not obtained. Therefore, the range of the electrode density of the present invention is preferably 1.2 g / cc or more and 2.5 g / cc or less.
　なお、本願明細書に記載の「電極密度」とは、炭素材料にリチウムコバルト酸化物を担持させた電極材料を、特定の溶媒としてＮ－メチルピロリドン、バインダとしてポリフッ化ビニリデンを用い、電極材料を１００としたときに溶媒を５０、バインダを５の重量割合にて形成したスラリーをアルミニウム箔上に塗布して乾燥し、アルミニウム箔上に電極層を作成し、この電極層の単位体積当たりの質量とする。具体的には、電極層の１ｃｍ2における電極層の厚み領域（体積）において、電極材料を含む固形分の重さを該体積で除した値とする。なお、前記固形分には、電極材料に加え、ポリフッ化ビニリデンも含めるものとする。 As used herein, “electrode density” refers to an electrode material in which lithium cobalt oxide is supported on a carbon material, N-methylpyrrolidone as a specific solvent, and polyvinylidene fluoride as a binder. A slurry in which the solvent was 50 and the binder was formed at a weight ratio of 5 was applied onto an aluminum foil and dried to create an electrode layer on the aluminum foil, and the mass per unit volume of the electrode layer And Specifically, in the thickness region (volume) of the electrode layer at 1 cm 2 of the electrode layer, a value obtained by dividing the weight of the solid content including the electrode material by the volume. In addition to the electrode material, the solid content includes polyvinylidene fluoride.
　本発明に係る電極材料の電極密度は、その製造工程において、リチウムコバルト酸化物の粒子径及びリチウムコバルト酸化物と炭素材料の配合比（ｗｔ％）、水熱合成の処理条件等の変更や、その他得られた電極材料をボールミルを行いまたは行わない等により調整できる。 In the production process, the electrode density of the electrode material according to the present invention is a change in the particle diameter of lithium cobalt oxide and the blending ratio of lithium cobalt oxide and carbon material (wt%), treatment conditions for hydrothermal synthesis, Other electrode materials obtained can be adjusted by performing ball milling or not.
（４）リチウムイオン二次電池
　本発明の電極材料は、リチウムイオン二次電池の正極のために好適である。したがって、本発明はまた、本発明の電極材料を含む電極層を有する正極と、負極と、負極と正極との間に配置された非水系電解液を保持したセパレータとを備えたリチウムイオン二次電池を提供する。 (4) Lithium ion secondary battery The electrode material of this invention is suitable for the positive electrode of a lithium ion secondary battery. Accordingly, the present invention also provides a lithium ion secondary comprising a positive electrode having an electrode layer containing the electrode material of the present invention, a negative electrode, and a separator holding a non-aqueous electrolyte disposed between the negative electrode and the positive electrode. Provide batteries.
　正極のための電極層は、必要に応じてバインダを溶解した溶媒（Ｎ－メチルピロリドンやイソプロピルアルコールなど）に、本発明の炭素材料にリチウムコバルト酸化物を担持させた電極材料を分散させ、得られた分散物をドクターブレード法などによって集電体上に塗工し、乾燥することにより作成することができる。また、得られた分散物を所定形状に成形し、集電体上に圧着しても良い。なお、本発明の電極材料、バインダを含む溶媒に、さらに金属酸化物や炭素材料を混合・分散させた混合溶媒を用い、混合物質層を形成することもできる。 An electrode layer for the positive electrode is obtained by dispersing an electrode material in which a lithium cobalt oxide is supported on the carbon material of the present invention in a solvent (N-methylpyrrolidone, isopropyl alcohol, etc.) in which a binder is dissolved, if necessary. The obtained dispersion can be prepared by coating on a current collector by a doctor blade method or the like and drying. Further, the obtained dispersion may be formed into a predetermined shape and may be pressure-bonded on the current collector. Note that a mixed material layer can also be formed by using a mixed solvent in which a metal oxide or a carbon material is further mixed and dispersed in the electrode material and binder-containing solvent of the present invention.
　集電体としては、白金、金、ニッケル、アルミニウム、チタン、鋼、カーボンなどの導電材料を使用することができる。集電体の形状は、膜状、箔状、板状、網状、エキスパンドメタル状、円筒状などの任意の形状を採用することができる。 As the current collector, a conductive material such as platinum, gold, nickel, aluminum, titanium, steel, or carbon can be used. As the shape of the current collector, any shape such as a film shape, a foil shape, a plate shape, a net shape, an expanded metal shape, and a cylindrical shape can be adopted.
　バインダとしては、ポリテトラフルオロエチレン、ポリフッ化ビニリデン、テトラフルオロエチレン－ヘキサフルオロプロピレンコポリマー、ポリフッ化ビニル、カルボキシメチルセルロースなどの公知のバインダが使用される。バインダの含有量は、混合材料の総量に対して１～３０質量％であるのが好ましい。１質量％以下であると電極層の強度が十分でなく、３０質量％以上であると、負極の放電容量が低下する、内部抵抗が過大になるなどの不都合が生じる。 As the binder, known binders such as polytetrafluoroethylene, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, polyvinyl fluoride, and carboxymethyl cellulose are used. The binder content is preferably 1 to 30% by mass with respect to the total amount of the mixed material. If it is 1% by mass or less, the strength of the electrode layer is not sufficient, and if it is 30% by mass or more, the discharge capacity of the negative electrode is reduced and internal resistance becomes excessive.
　負極としては、一般的なリチウムイオン二次電池において使用されている黒鉛電極の他、公知の負極活物質を含む電極層を備えた負極を特に限定無く使用することができる。負極活物質の例としては、Ｆｅ２Ｏ３、ＭｎＯ、ＭｎＯ２、Ｍｎ２Ｏ３、Ｍｎ３Ｏ４、ＣｏＯ、Ｃｏ３Ｏ４、ＮｉＯ、Ｎｉ２Ｏ３、ＴｉＯ、ＴｉＯ２、ＳｎＯ、ＳｎＯ２、ＳｉＯ２、ＲｕＯ２、ＷＯ、ＷＯ２、ＺｎＯ等の酸化物、Ｓｎ、Ｓｉ、Ａｌ、Ｚｎ等の金属、ＬｉＶＯ２、Ｌｉ３ＶＯ４、Ｌｉ４Ｔｉ５Ｏ１２などの複合酸化物、Ｌｉ２．６Ｃｏ０．４Ｎ、Ｇｅ３Ｎ４、Ｚｎ３Ｎ２、Ｃｕ３Ｎなどの窒化物を挙げることができる。 As the negative electrode, in addition to the graphite electrode used in a general lithium ion secondary battery, a negative electrode provided with an electrode layer containing a known negative electrode active material can be used without any particular limitation. Examples of the negative electrode active material include Fe 2 O 3 , MnO, MnO 2 , Mn 2 O 3 , Mn 3 O 4 , CoO, Co 3 O 4 , NiO, Ni 2 O 3 , TiO, TiO 2 , SnO, SnO 2 , oxides such as SiO 2 , RuO 2 , WO, WO 2 , ZnO, metals such as Sn, Si, Al, Zn, composite oxides such as LiVO 2 , Li 3 VO 4 , Li 4 Ti 5 O 12 , Examples thereof include nitrides such as Li 2.6 Co 0.4 N, Ge 3 N 4 , Zn 3 N 2 , and Cu 3 N.
　負極のための電極層は、必要に応じてバインダを溶解した溶媒に、上記負極電極質と導電剤とを分散させ、得られた分散物をドクターブレード法などによって集電体上に塗工し、乾燥することにより作成することができる。また、得られた分散物を所定形状に成形し、集電体上に圧着しても良い。 The electrode layer for the negative electrode is dispersed on the current collector by the doctor blade method or the like by dispersing the negative electrode electrode material and the conductive agent in a solvent in which a binder is dissolved as necessary. It can be created by drying. Further, the obtained dispersion may be formed into a predetermined shape and may be pressure-bonded on the current collector.
　集電体及びバインダについては、正極のための集電体及びバインダについての記載が負極においてもあてはまる。導電剤としては、カーボンブラック、天然黒鉛、人造黒鉛などの炭素粉末を使用することができる。 For the current collector and binder, the description of the current collector and binder for the positive electrode also applies to the negative electrode. As the conductive agent, carbon powder such as carbon black, natural graphite, and artificial graphite can be used.
　セパレータとしては、例えばポリオレフィン繊維不織布、ガラス繊維不織布などが好適に使用される。セパレータに保持される電解液は、非水系溶媒に電解質を溶解させた電解液が使用され、公知の非水系電解液を特に制限なく使用することができる。 As the separator, for example, a polyolefin fiber nonwoven fabric or a glass fiber nonwoven fabric is preferably used. As the electrolytic solution retained in the separator, an electrolytic solution in which an electrolyte is dissolved in a non-aqueous solvent is used, and a known non-aqueous electrolytic solution can be used without any particular limitation.
　非水系電解液の溶媒としては、電気化学的に安定なエチレンカーボネート、プロピレンカーボネート、ブチレンカーボネート、ジメチルカーボネート、エチルメチルカーボネート、ジエチルカーボネート、スルホラン、３－メチルスルホラン、γ－ブチロラクトン、アセトニトリル及びジメトキシエタン、Ｎ－メチル－２－ピロリドン、ジメチルホルムアミド又はこれらの混合物を好適に使用することができる。 Examples of the solvent for the non-aqueous electrolyte include electrochemically stable ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, sulfolane, 3-methyl sulfolane, γ-butyrolactone, acetonitrile, and dimethoxyethane, N-methyl-2-pyrrolidone, dimethylformamide or a mixture thereof can be preferably used.
　非水系電解液の溶質としては、有機電解液に溶解したときにリチウムイオンを生成する塩を、特に限定なく使用することができる。例えば、ＬｉＰＦ６、ＬｉＢＦ４、ＬｉＣｌＯ４、ＬｉＮ（ＣＦ３ＳＯ２）２、ＬｉＣＦ３ＳＯ３、ＬｉＣ（ＳＯ２ＣＦ３）３、ＬｉＮ（ＳＯ２Ｃ２Ｆ５）２、ＬｉＡｓＦ６、ＬｉＳｂＦ６、又はこれらの混合物を好適に使用することができる。非水系電解液の溶質として、リチウムイオンを生成する塩に加えて、第４級アンモニウムカチオン又は第４級ホスホニウムカチオンを有する第４級アンモニウム塩又は第４級ホスホニウム塩を使用することができる。例えば、Ｒ１Ｒ２Ｒ３Ｒ４Ｎ＋又はＲ１Ｒ２Ｒ３Ｒ４Ｐ＋で表されるカチオン（ただし、Ｒ１、Ｒ２、Ｒ３、Ｒ４は炭素数１～６のアルキル基を表す）と、ＰＦ６ －、ＢＦ４ －、ＣｌＯ４ －、Ｎ（ＣＦ３ＳＯ３）２ －、ＣＦ３ＳＯ３ －、Ｃ（ＳＯ２ＣＦ３）３ －、Ｎ（ＳＯ２Ｃ２Ｆ５）２ －、ＡｓＦ６ －又はＳｂＦ６ －からなるアニオンとからなる塩、又はこれらの混合物を好適に使用することができる。 As a solute of the nonaqueous electrolytic solution, a salt that generates lithium ions when dissolved in an organic electrolytic solution can be used without any particular limitation. For example, LiPF 6, LiBF 4, LiClO 4, LiN (CF 3 SO 2) 2, LiCF 3 SO 3, LiC (SO 2 CF 3) 3, LiN (SO 2 C 2 F 5) 2, LiAsF 6, LiSbF 6 Or a mixture thereof can be preferably used. As a solute of the nonaqueous electrolytic solution, a quaternary ammonium salt or a quaternary phosphonium salt having a quaternary ammonium cation or a quaternary phosphonium cation can be used in addition to a salt that generates lithium ions. For example, a cation represented by R 1 R 2 R 3 R 4 N + or R 1 R 2 R 3 R 4 P + (where R 1 , R 2 , R 3 and R 4 are alkyls having 1 to 6 carbon atoms) Group), PF 6 − , BF 4 − , ClO 4 − , N (CF 3 SO 3 ) 2 − , CF 3 SO 3 − , C (SO 2 CF 3 ) 3 − , N (SO 2 C 2 A salt composed of an anion composed of F 5 ) 2 − , AsF 6 — or SbF 6 — , or a mixture thereof can be preferably used.
［特性比較（ＬｉＣｏＯ２／ＫＢ）］
　本製造方法で得られた二次電池用電極材料の特性を確認する。本実施例及び比較例では、以下の条件により電極材料を作成し、当該電極材料を二次電池用電極材料として用いた電池を作成してエネルギー密度及びレート特性を測定した。 [Characteristic comparison (LiCoO 2 / KB)]
The characteristic of the electrode material for secondary batteries obtained by this manufacturing method is confirmed. In this example and comparative example, an electrode material was prepared under the following conditions, a battery using the electrode material as an electrode material for a secondary battery was prepared, and energy density and rate characteristics were measured.
（実施例１）
　図３に示すように、まず、ケッチェンブラック（ＫＢ）と、材料源となるコバルト源であるＣｏ（ＣＨ３ＣＯＯ）２・４Ｈ２Ｏと、蒸留水とを混合した反応液を調整（調整工程）し、この反応液に対して５０ｍ／ｓの回転速度で５分間のＵＣ処理を行った。ＵＣ処理を終えた反応液に対しては、リチウム源としてＬｉＨＯ・Ｈ２Ｏを加えて、さらに５０ｍ／ｓの回転速度で５分間のＵＣ処理を行った。このＵＣ処理では、６６０００Ｎ（ｋｇｍｓ－２）の遠心力が加わっている。この第１，２回目のＵＣ処理は、ＵＣ処理によるＬｉＣｏＯ2の前駆体を炭素材料に担持させる前駆体担持工程に対応する。 (Example 1)
As shown in FIG. 3, first, a reaction liquid prepared by mixing ketjen black (KB), Co (CH 3 COO) 2 .4H 2 O, which is a cobalt source as a material source, and distilled water is prepared (adjusted). Then, the reaction solution was subjected to UC treatment for 5 minutes at a rotational speed of 50 m / s. The reaction solution that had been subjected to the UC treatment was added with LiHO.H 2 O as a lithium source, and further subjected to a UC treatment for 5 minutes at a rotational speed of 50 m / s. In this UC process, a centrifugal force of 66000 N (kgms −2 ) is applied. The first and second UC processes correspond to a precursor supporting process in which a LiCoO 2 precursor by UC process is supported on a carbon material.
　そして、得られた溶液を濾過・乾燥し、さらに大気中などの酸化雰囲気中で２５０℃まで急速加熱し、１時間の間保持することで予備加熱処理を行う。予備熱処理後、オートクレーブ内にＨ２Ｏと、予備加熱処理によって作製した前駆体と、Ｈ２Ｏ２とを加えて、水熱合成を行い２５０℃で６時間保持し、ＫＢにＬｉＣｏＯ2を担持させた電極材料を得た。このときの圧力は３９．２気圧である。この水熱合成は、熱処理行程に対応する。なお、このとき、電極材料中のＬｉＣｏＯ2が８０ｗｔ％、ＫＢが２０ｗｔ％となるように調整している。 Then, the obtained solution is filtered and dried, further rapidly heated to 250 ° C. in an oxidizing atmosphere such as the air, and kept for 1 hour to perform a preheating treatment. After the preliminary heat treatment, H 2 O, the precursor prepared by the pre-heating treatment, and H 2 O 2 are added to the autoclave, hydrothermal synthesis is performed, and the mixture is held at 250 ° C. for 6 hours, and LiCoO 2 is supported on the KB. An electrode material was obtained. The pressure at this time is 39.2 atmospheres. This hydrothermal synthesis corresponds to the heat treatment process. At this time, adjustment is made so that LiCoO 2 in the electrode material is 80 wt% and KB is 20 wt%.
その後、得られたＫＢにＬｉＣｏＯ2を担持させた電極材料（粉体）をバインダとしてのポリフッ化ビニリデン（ＰＶＤＦ）、溶媒としてのＮ－メチルピロリドン（ＮＭＰ）と共に（ＬｉＣｏＯ2／ＫＢ／ＰＶＤＦ／ＮＭＰ　８０：２０：５：５０／ｗｔ％）分散して、電極スラリーを作成した。この電極スラリーをＳＵＳ板上に溶接されたＳＵＳメッシュ中に投入して乾燥し、１０μｍの電極厚みの電極層を形成し、作用電極Ｗ．Ｅ．とした。この電極層の１ｃｍ３におけるその厚み領域（体積）における固形分の重さを体積で除した値を測定し電極密度として表１に示す（以下の実施例及び比較例で示す電極密度はこの手法で測定している）。そして、前記電極層上にセパレータと対極Ｃ．Ｅ．及び参照極としてＬｉフォイルを乗せ、電解液として、１ＭのＬｉＰＦ６のエチレンカーボネート／ジエチルカーボネート１：１溶液を浸透させて、電池セルとした。 Thereafter, an electrode material (powder) in which LiCoO 2 is supported on the obtained KB is used together with polyvinylidene fluoride (PVDF) as a binder and N-methylpyrrolidone (NMP) as a solvent (LiCoO 2 / KB / PVDF / NMP). 80: 20: 5: 50 / wt%) was dispersed to prepare an electrode slurry. This electrode slurry was put into a SUS mesh welded on a SUS plate and dried to form an electrode layer having an electrode thickness of 10 μm. E. It was. A value obtained by dividing the weight of the solid content in the thickness region (volume) at 1 cm 3 of this electrode layer by the volume was measured and shown as an electrode density in Table 1 (the electrode density shown in the following examples and comparative examples is the method) ). A separator and a counter electrode C. are formed on the electrode layer. E. In addition, a Li foil was placed as a reference electrode, and a 1M LiPF6 ethylene carbonate / diethyl carbonate 1: 1 solution was infiltrated as an electrolyte solution to obtain a battery cell.
（実施例２～実施例５）
実施例２～実施例５では、実施例１で作成したＫＢにＬｉＣｏＯ2を担持させた電極材料において、水熱合成の処理温度及び処理時間を変更し、表１に示す電極密度となる電極材料を作製した。その電極材料を用いて実施例２～実施例５の電池を作成した。実施例２～実施例５では、電極材料中のＬｉＣｏＯ2が８０ｗｔ％、ＫＢが２０ｗｔ％となるように調整している。 (Example 2 to Example 5)
In Examples 2 to 5, in the electrode material in which LiCoO 2 was supported on the KB prepared in Example 1, the treatment temperature and treatment time of hydrothermal synthesis were changed, and the electrode materials having the electrode densities shown in Table 1 were obtained. Was made. Using the electrode material, batteries of Examples 2 to 5 were produced. In Examples 2 to 5, adjustment is made so that LiCoO 2 in the electrode material is 80 wt% and KB is 20 wt%.
（比較例１）
　電極密度をさらに高密度化するため、実施例１で作成したＫＢにＬｉＣｏＯ2を担持させた電極材料において、水熱合成の処理温度及び処理時間を変更して検討を行ったが、２．８ｇ／ｃｃの電極密度の電極材料を作製するのは困難であった。代わりに、実施例１で作成したＫＢにＬｉＣｏＯ2を担持させた電極材料を、さらに、電極密度を高密度化するためにボールミルを行い、表１に記載の電極密度を高めた電極材料を得た。そして、この電極材料を用いて比較例１の電池を作成した。比較例１の電池は、ボールミルによって、高密度化処理した電極材料を電極層に用いた以外は実施例１と同様の手法を用いて比較例１の電池を作成している。 (Comparative Example 1)
In order to further increase the electrode density, the electrode material in which LiCoO 2 was supported on KB prepared in Example 1 was examined by changing the treatment temperature and treatment time of hydrothermal synthesis. It was difficult to produce an electrode material having an electrode density of / cc. Instead, the electrode material in which LiCoO 2 was supported on the KB prepared in Example 1 was further ball milled to increase the electrode density, and the electrode material having an increased electrode density shown in Table 1 was obtained. It was. And the battery of the comparative example 1 was created using this electrode material. The battery of Comparative Example 1 was prepared by using the same method as in Example 1 except that the electrode material subjected to densification treatment was used for the electrode layer by a ball mill.
　（結果）
実施例１～実施例５の電池及び比較例１の電池について、１０Ｃレートでのエネルギー密度及びレート特性を評価し、その結果を表１に示す。なお、レート特性は、０．１Ｃのエネルギー密度に対する１０Ｃのエネルギー密度の維持率（％）を示す。 (result)
Regarding the batteries of Examples 1 to 5 and the battery of Comparative Example 1, the energy density and rate characteristics at 10 C rate were evaluated, and the results are shown in Table 1. The rate characteristic indicates the maintenance rate (%) of the energy density of 10C with respect to the energy density of 0.1C.
Figure JPOXMLDOC01-appb-T000001
  
Figure JPOXMLDOC01-appb-T000001
  
表１に示すとおり、比較例１の電極材料を用いた電池セルは、電極密度が高いにも関わらず実施例１～実施例５の電極材料を用いた電池セルに比較して、１０Ｃでのエネルギー密度著しく小さい値を示し、レート特性も低い値を示した。これに対し、実施例１の電極材料を用いた電池セルは、エネルギー密度及びレート特性が極めて良好であり、電極密度が低い実施例１であっても２００Ｗｈ／Ｌを超えるエネルギー密度を有していた。 As shown in Table 1, the battery cell using the electrode material of Comparative Example 1 has a 10C compared to the battery cell using the electrode material of Examples 1 to 5 despite the high electrode density. The energy density was remarkably small, and the rate characteristics were also low. On the other hand, the battery cell using the electrode material of Example 1 has extremely good energy density and rate characteristics, and has an energy density exceeding 200 Wh / L even in Example 1 where the electrode density is low. It was.
また、図４には、実施例３において、電極作成前の炭素材料（ＫＢ）にＬｉＣｏＯ2を担持させた電極材料のＳＥＭ像（×１０ｋ）を示す。また図５には、さらに実施例３における電極材料のＳＥＭ像（×５０ｋ）を示す。 FIG. 4 shows an SEM image (× 10 k) of an electrode material in which LiCoO 2 is supported on a carbon material (KB) before electrode preparation in Example 3. FIG. 5 further shows an SEM image (× 50 k) of the electrode material in Example 3.
　図４に示すように、実施例３では、微細なナノ粒子を見て取ることができる。また、倍率を上げて観察した図５においては、実施例３の電極材料を観察すると、比較的粒子径の大きなＬｉＣｏＯ２粒子（粒子径１１０～５００ｎｍ）と、比較的粒子径の小さなＬｉＣｏＯ２粒子（粒子径５～１１０ｎｍ未満）とが担持されていることがわかる。なお、この比較的粒子径の小さなＬｉＣｏＯ２粒子は、粒子径の大きなＬｉＣｏＯ２粒子の表面に担持されていているものもある。これらのＬｉＣｏＯ２粒子がナノレベルで高分散されていることが分かる。 As shown in FIG. 4, in Example 3, fine nanoparticles can be seen. Further, in FIG. 5 was observed by increasing the magnification, when observing the electrode material of Example 3, a relatively particle size large LiCoO 2 particles (particle diameter 110 ~ 500 nm), relatively particle size small LiCoO 2 particles (Particle diameter 5 to less than 110 nm) is supported. Some of the LiCoO 2 particles having a relatively small particle diameter are supported on the surface of the LiCoO 2 particles having a large particle diameter. It can be seen that these LiCoO 2 particles are highly dispersed at the nano level.
［ＬｉＣｏＯ2とＫＢ+ＣＮＦとの配合割合］
　炭素材料にＬｉＣｏＯ2を担持させた電極材料について、ＬｉＣｏＯ2と炭素材料の配合割合（ｗｔ％）について検討した。 [Mixing ratio of LiCoO 2 and KB + CNF]
Regarding the electrode material in which LiCoO 2 is supported on the carbon material, the mixing ratio (wt%) of LiCoO 2 and the carbon material was examined.
（実施例６～実施例８）
　実施例３の電極材料の電極材料中の炭素材料の割合以外を同条件とし、炭素材料として、ＫＢに加えＣＮＦを混合した。また、ＬｉＣｏＯ2と炭素材料（ＫＢとＣＮＦ）との配合割合を変更して電極材料を得、これらの電極材料を用いて実施例６～実施例８の電池を作成した。この時の、実施例６～実施例８の電極材料中のＬｉＣｏＯ2、ＫＢ、ＣＮＦの割合は、表２に示すとおりである。 (Examples 6 to 8)
The conditions other than the ratio of the carbon material in the electrode material of Example 3 were the same, and CNF was mixed as a carbon material in addition to KB. In addition, electrode materials were obtained by changing the blending ratio of LiCoO 2 and carbon materials (KB and CNF), and batteries of Examples 6 to 8 were made using these electrode materials. The ratios of LiCoO 2 , KB, and CNF in the electrode materials of Examples 6 to 8 at this time are as shown in Table 2.
　（結果）
実施例６～実施例８の電池について、１０Ｃレートでのエネルギー密度及びレート特性を評価し、その結果を表２に示す。なお、レート特性は、０．１Ｃのエネルギー密度に対する１０Ｃのエネルギー密度の維持率（％）を示す。 (result)
The batteries of Examples 6 to 8 were evaluated for energy density and rate characteristics at a 10 C rate, and the results are shown in Table 2. The rate characteristic indicates the maintenance rate (%) of the energy density of 10C with respect to the energy density of 0.1C.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
表２に示すとおり、実施例６～実施例８の電池は、１０Ｃレートでのエネルギー密度がいずれも２００Ｗｈ／Ｌを超え、且つレート特性も良好な値を有していた。なかでも、ＬｉＣｏＯ2を７０ｗｔ％以上配合した実施例７及び実施例８の電池セルは、エネルギー密度が極めて良好であった。また炭素材料として、球状であるＫＢと繊維状のＣＮＦを混合させることでその容量が向上する結果となった。 As shown in Table 2, the batteries of Examples 6 to 8 all had an energy density at 10 C rate exceeding 200 Wh / L, and the rate characteristics had good values. Especially, the energy density of the battery cells of Example 7 and Example 8 in which 70% by weight or more of LiCoO 2 was blended was extremely good. Moreover, it became a result that the capacity | capacitance improved by mixing spherical KB and fibrous CNF as a carbon material.
１…外筒
１－２…せき板
１－３…内壁
２…内筒
２－１…貫通孔 DESCRIPTION OF SYMBOLS 1 ... Outer cylinder 1-2 ... Baffle 1-3 ... Inner wall 2 ... Inner cylinder 2-1 ... Through-hole

Claims (8)

  1. 　炭素材料にリチウムコバルト酸化物を担持させた電極材料であって、
    　電極密度が２．５ｇ／ｃｃ以下の範囲であることを特徴とする電極材料。     An electrode material in which a lithium cobalt oxide is supported on a carbon material,
    An electrode material having an electrode density in the range of 2.5 g / cc or less.
  2. 　前記リチウムコバルト酸化物は、電極材料中の７０ｗｔ％以上含有され、また炭素材料は、電極材料中の３０ｗｔ％以下含有されていることを特徴とする請求項１に記載の電極材料。 2. The electrode material according to claim 1, wherein the lithium cobalt oxide is contained in an amount of 70 wt% or more in the electrode material, and the carbon material is contained in an amount of 30 wt% or less in the electrode material.
  3. 　前記炭素材料は、繊維状炭素と球状炭素とが混合されていることを特徴とする請求項１又は２に記載の電極材料。 The electrode material according to claim 1 or 2, wherein the carbon material is a mixture of fibrous carbon and spherical carbon.
  4. 　前記リチウムコバルト酸化物は、２つの粒子径分布を有することを特徴とする請求項１乃至３のいずれか１項に記載の電極材料。 The electrode material according to any one of claims 1 to 3, wherein the lithium cobalt oxide has two particle size distributions.
  5. 　前記リチウムコバルト酸化物は、５～１１０ｎｍ未満の粒子径分布と、１１０～５００ｎｍの粒子径分布を有することを特徴とする請求項４に記載の電極材料。 5. The electrode material according to claim 4, wherein the lithium cobalt oxide has a particle size distribution of 5 to less than 110 nm and a particle size distribution of 110 to 500 nm.
  6. 　請求項１乃至５のいずれかに記載の電極材料を用いて形成された電極を備えた蓄電デバイス。 An electricity storage device comprising an electrode formed using the electrode material according to any one of claims 1 to 5.
  7. 　炭素材料にリチウムコバルト酸化物を担持させた電極材料の製造方法であって、
    　リチウムコバルト酸化物の材料源と炭素材料を含有する反応液にずり応力と遠心力とを加えることにより、炭素材料にリチウムコバルト酸化物の前駆体を担持させる前駆体担持工程と、
    　前記炭素材料に担持させたリチウムコバルト酸化物の前駆体に加熱処理を行い、炭素材料に担持させたナノ化したリチウムコバルト酸化物を得る熱処理工程と、を有し
    　得られた電極材料の電極密度が２．５ｇ／ｃｃ以下の範囲であることを特徴とする電極材料の製造方法。     A method for producing an electrode material in which a lithium cobalt oxide is supported on a carbon material,
    A precursor supporting step of supporting a precursor of lithium cobalt oxide on the carbon material by applying shear stress and centrifugal force to the reaction solution containing the material source of lithium cobalt oxide and the carbon material;
    A heat treatment step of performing a heat treatment on the precursor of the lithium cobalt oxide supported on the carbon material to obtain a nanolithium lithium cobalt oxide supported on the carbon material, and an electrode density of the obtained electrode material Is in the range of 2.5 g / cc or less.
  8. 　前記熱処理工程は、
    　酸素を含む雰囲気下で処理を行うことを特徴とする請求項７に記載の電極材料の製造方法。     The heat treatment step includes
    The method for producing an electrode material according to claim 7, wherein the treatment is performed in an atmosphere containing oxygen.
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