Classifications

• • 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
  • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
  • C01G51/00—Compounds of cobalt
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
  • C01G51/00—Compounds of cobalt
  • C01G51/40—Complex oxides containing cobalt and at least one other metal element
  • C01G51/42—Complex oxides containing cobalt and at least one other metal element containing alkali metals, e.g. LiCoO2
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/05—Accumulators with non-aqueous electrolyte
  • H01M10/052—Li-accumulators
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • 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
  • H01M4/04—Processes of manufacture in general
  • H01M4/0471—Processes of manufacture in general involving thermal treatment, e.g. firing, sintering, backing particulate active material, thermal decomposition, pyrolysis
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/13—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
• • 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
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
  • H01M2004/028—Positive electrodes
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/10—Energy storage using batteries

Definitions

• the present invention relates to a positive electrode active material for a lithium secondary battery, a method for producing the same, and a lithium secondary battery using the positive electrode active material.
• lithium-ion secondary batteries have been put into practical use as power sources for small electronic devices such as laptop computers, mobile phones, and video cameras.
• this lithium-ion secondary battery research and development on lithium-based composite oxides have been active since it was reported in 1980 that lithium cobalt oxide was useful as a positive electrode active material for lithium-ion secondary batteries by Mizushima et al. And many proposals have been made so far.
• a lithium secondary battery using lithium cobalt oxide has a problem of deterioration of cycle characteristics due to elution of cobalt atoms.
• Patent Document 1 proposes a lithium secondary battery in which a positive electrode active material is a lithium-cobalt-based composite oxide having a titanium content of 20% or more on the surface of lithium cobalt oxide particles.
• Patent Document 2 discloses a positive electrode active material for a lithium secondary battery, which comprises a lithium transition metal composite oxide containing 0.20 to 2.00% by weight of Ti atoms, and the Ti atoms are lithium transition metals. It has been proposed to use a lithium cobalt-based composite oxide that exists in the depth direction from the particle surface of the composite oxide and has the maximum concentration gradient on the particle surface as the positive electrode active material.
• Patent Document 3 and Patent Document 4 below propose that a lithium cobalt composite oxide containing Sr atoms and Ti atoms is used as a positive electrode active material.
• an object of the present invention is to provide a positive electrode active material for a lithium secondary battery, which has excellent cycle characteristics, a small decrease in average operating voltage, a high average operating voltage, and a high energy density retention rate.
• An object of the present invention is to provide a lithium secondary battery that is industrially advantageous, has excellent cycle characteristics and average operating voltage characteristics, and has a high energy density maintenance rate.
• the present inventors have conducted extensive studies in view of the above circumstances, and as a result, by using a mixture of titanium-containing lithium cobalt composite oxide particles and inorganic fluoride particles as a positive electrode active material of a lithium secondary battery, it was excellent.
• the inventors have found that the lithium secondary battery has cycle characteristics, a small decrease in average operating voltage, a high average operating voltage, and a high energy density maintenance rate.
• the present invention (1) provides a positive electrode active material for a lithium secondary battery, which comprises a mixture of titanium-containing lithium cobalt composite oxide particles and inorganic fluoride particles.
• the content of Ti in the titanium-containing lithium cobalt composite oxide particles is 0.05 to 2.0 mol in terms of Ti atoms with respect to Co atoms in the lithium cobalt composite oxide particles.
• the positive electrode active material for a lithium secondary battery according to (1) is provided.
• the titanium-containing lithium cobalt composite oxide particles are one or two selected from the group consisting of Ca, Mg, Sr, Zr, Al, Nb, B and W (M element).
• the present invention provides the positive electrode active material for a lithium secondary battery according to (1) or (2), which contains at least one species.
• the present invention (4) is characterized in that the titanium-containing lithium cobalt composite oxide particles contain, as the M element, at least one kind or two or more kinds selected from Ca, Mg, Sr, Zr and Al. (3) A positive electrode active material for lithium secondary batteries is provided.
• the present invention (5) is characterized in that the titanium-containing lithium cobalt composite oxide particles contain Mg, Sr, Zr and Al as M elements, the positive electrode active material for a lithium secondary battery according to (3). It provides a substance.
• the content of the inorganic fluoride particles is 0.05 to 2.0 mol% in terms of F atoms with respect to the Co atoms in the titanium-containing lithium cobalt composite oxide particles.
• the present invention provides the positive electrode active material for a lithium secondary battery according to any one of (1) to (5).
• the present invention (7) comprises the positive electrode active material for a lithium secondary battery according to any one of (1) to (6), characterized in that the inorganic fluoride particles contain MgF 2 and / or AlF 3. It is provided.
• this invention (8) is the 1st process of mixing the titanium-containing lithium cobalt composite oxide particles and the inorganic fluoride particles to obtain a mixture of the titanium-containing lithium cobalt composite oxide particles and the inorganic fluoride particles.
• the present invention provides a method for producing a positive electrode active material for a lithium secondary battery, which comprises:
• the present invention (9) also provides the method for producing a positive electrode active material for a lithium secondary battery according to (8), wherein the mixing treatment in the first step is performed by dry mixing.
• the present invention provides the method for producing a positive electrode active material for a lithium secondary battery according to (9), wherein the dry mixing treatment of the first step is performed in the presence of water. Is.
• the present invention (11) provides the method for producing a positive electrode active material for a lithium secondary battery according to (8), wherein the mixing treatment in the first step is performed by wet mixing.
• the present invention (12) is characterized by further comprising a second step of heat-treating the mixture of the titanium-containing lithium cobalt composite oxide particles obtained by performing the first step and the inorganic fluoride particles (8).
• )-(11) A method for producing a positive electrode active material for a lithium secondary battery is provided.
• the present invention (13) provides the method for producing a positive electrode active material for a lithium secondary battery according to (12), wherein the temperature of the heat treatment in the second step is 200 to 1100 ° C. is there.
• the titanium-containing lithium cobalt composite oxide particles are one kind or two kinds selected from the group of Ca, Mg, Sr, Zr, Al, Nb, B and W (M element).
• the present invention provides a lithium secondary battery, wherein the positive electrode active material for a lithium secondary battery according to any one of (1) to (7) is used as the positive electrode active material. Is.
• the positive electrode active material for lithium secondary batteries which is excellent in cycle characteristics, the average operating voltage is less decreased, the average operating voltage is maintained high, and the energy density retention rate can be further increased, and its industrial use. It is possible to provide a lithium secondary battery having an excellent manufacturing method, excellent cycle characteristics, and characteristics of average operating voltage and a high energy density retention rate.
• the positive electrode active material for a lithium secondary battery of the present invention is a positive electrode active material for a lithium secondary battery, which comprises a mixture of titanium-containing lithium cobalt composite oxide particles and inorganic fluoride particles.
• the titanium-containing lithium cobalt composite oxide forming the titanium-containing lithium cobalt composite oxide particles according to the positive electrode active material for a lithium secondary battery of the present invention is a composite oxide containing at least lithium, cobalt and titanium, and lithium cobalt It is a composite oxide in which titanium is added as an additional element to the composite oxide.
• the lithium-cobalt composite oxide contains titanium, the characteristics of average operating voltage are improved.
• the atomic ratio of Li to Co in atomic conversion is preferably 0.90 to 1.20, particularly preferably 0.95 to 1.15.
• the energy density of the positive electrode active material for a lithium secondary battery increases.
• the mol% of Ti with respect to Co in terms of atom ((Ti / Co) ⁇ 100) is preferably 0.05 to 2.0 mol%, particularly preferably 0.1 to 1. It is 5 mol%.
• the atomic% of Ti in terms of atom with respect to Co in the titanium-containing lithium-cobalt composite oxide ((Li / Co) ⁇ 100) is within the above range, the characteristics of the average operating voltage are improved.
• Ti may exist only inside the composite oxide particles or may exist inside and on the surface of the composite oxide particles. May exist inside the complex oxide particles or may exist on the surface of the complex oxide particles.
• the titanium-containing lithium cobalt composite oxide particles are those in which Ti is present as a solid solution at least inside the composite oxide particles, It is preferable in that the structure of the composite oxide is stabilized.
• the presence of Ti as a solid solution in at least the inside of the composite oxide particles means that Ti exists only inside the particles or both inside the particles and on the surface of the particles.
• the titanium-containing lithium-cobalt composite oxide contains Ti as an essential additional element of the lithium-cobalt composite oxide, but for the purpose of improving performance or physical properties, the titanium-containing lithium-cobalt composite oxide further contains M element shown below. Any one of them or two or more of them can be contained.
• the M element contained in the titanium-containing lithium cobalt composite oxide as required is Ca, Mg, Sr, Zr, Al, Nb, B and W.
• the titanium-containing lithium-cobalt composite oxide preferably contains Ca and / or Sr as the M element from the viewpoint that the battery characteristics are further enhanced, and Ca and / or Sr and Mg, Zr, Al, Nb, It is particularly preferable to contain one or more selected from B and W. Further, the titanium-containing lithium cobalt composite oxide particles preferably contain, as the M element, at least one kind or two or more kinds selected from Ca, Mg, Sr, Zr and Al. The titanium-containing lithium cobalt composite oxide particles preferably contain Mg, Sr, Zr and Al as the M element.
• the mol% ((M / Co) ⁇ 100) in atomic conversion of M element to Co atom in the titanium-containing lithium-cobalt composite oxide is preferably 0. It is from 01 to 3.0 mol%, particularly preferably from 0.05 to 2.0 mol%.
• the atomic% mol% of M element to Co atom in the titanium-containing lithium-cobalt composite oxide ((M / Co) ⁇ 100) is within the above range. Thereby, the battery characteristics can be improved without impairing the charge / discharge capacity.
• the number of moles of M element in terms of atom which is the basis of calculation of the above mol%, is the total number of moles of each M element. Point to.
• the atomic% mol% ((M / Co) ⁇ 100) of the M element with respect to the Co atom is preferably 0.01 to 2.0 mol%, particularly preferably 0.05 to 1.0 mol%.
• the titanium-containing lithium cobalt composite oxide contains two or more kinds selected from the group of Ca, Mg, Sr, Zr, Al, Nb, B and W as the M element, Co in the titanium-containing lithium cobalt composite oxide
• the mol% ((M / Co) ⁇ 100) of the element M in terms of atoms is within the above range, battery characteristics such as cycle performance, load characteristics, and safety can be satisfied at the same time.
• the atomic% of Ca in terms of Co atoms in the titanium-containing lithium cobalt composite oxide ((Ca / Co) ⁇ 100) is preferably 0. 0.01 to 2.0 mol%, particularly preferably 0.05 to 1.0 mol%.
• the mol% ((Mg / Co) ⁇ 100) of Mg in terms of Co atoms in the titanium-containing lithium-cobalt composite oxide is preferably 0. 0.01 to 2.0 mol%, particularly preferably 0.05 to 1.0 mol%.
• the atomic% mol% of Sr to Co atom in the titanium-containing lithium cobalt composite oxide ((Sr / Co) ⁇ 100) is preferably 0. 0.01 to 2.0 mol%, particularly preferably 0.05 to 1.0 mol%.
• the mol% ((Zr / Co) ⁇ 100) of Zr with respect to Co atoms in the titanium-containing lithium cobalt composite oxide is preferably 0. 0.01 to 2.0 mol%, particularly preferably 0.05 to 1.0 mol%.
• the atomic percentage of Al in terms of Co atoms in the titanium-containing lithium-cobalt composite oxide ((Al / Co) ⁇ 100) is preferably 0. 0.01 to 2.0 mol%, particularly preferably 0.05 to 1.0 mol%.
• the mol% ((Nb / Co) ⁇ 100) of Nb with respect to Co atoms in the titanium-containing lithium-cobalt composite oxide is preferably 0. 0.01 to 2.0 mol%, particularly preferably 0.05 to 1.0 mol%.
• the atomic percentage of B atom relative to Co atoms in the titanium-containing lithium-cobalt composite oxide ((B / Co) ⁇ 100) is preferably 0. 0.01 to 2.0 mol%, particularly preferably 0.05 to 1.0 mol%.
• the atomic% of W in terms of Co atom in the titanium-containing lithium-cobalt composite oxide ((W / Co) ⁇ 100) is preferably 0. 0.01 to 2.0 mol%, particularly preferably 0.05 to 1.0 mol%.
• the element M may be present inside the titanium-containing lithium cobalt composite oxide particles or may be present on the surface of the titanium-containing lithium cobalt composite oxide particles, and is a particle of the titanium-containing lithium cobalt composite oxide particles. It may be present both inside and on the surface of the particles.
• the M element When the M element is present on the particle surface of the titanium-containing lithium cobalt composite oxide, the M element may be present in the form of oxide, composite oxide, sulfate, phosphate or the like.
• the titanium-containing lithium cobalt composite oxide particles are particles of the titanium-containing lithium cobalt composite oxide.
• the average particle size of the titanium-containing lithium cobalt composite oxide particles is a particle size (D50) of 50% in volume integration in the particle size distribution determined by a laser diffraction / scattering method, preferably 0.5 to 30 ⁇ m, and particularly preferably 3 to It is 25 ⁇ m.
• the BET specific surface area of the titanium-containing lithium cobalt composite oxide particles is preferably 0.05 to 1.0 m 2 / g, particularly preferably 0.15 to 0.6 m 2 / g. When the average particle diameter or BET specific surface area of the titanium-containing lithium cobalt composite oxide particles is within the above range, preparation of the positive electrode mixture and coatability are facilitated, and an electrode having a high filling property is obtained.
• Titanium-containing lithium cobalt composite oxide particles for example, a raw material mixing step of preparing a raw material mixture containing a lithium compound, a cobalt compound, and a titanium compound, and then performing a firing step of firing the resulting raw material mixture.
• a raw material mixing step of preparing a raw material mixture containing a lithium compound, a cobalt compound, and a titanium compound, and then performing a firing step of firing the resulting raw material mixture.
• the lithium compound according to the raw material mixing step is not particularly limited as long as it is a lithium compound used as a raw material for producing a lithium cobalt composite oxide, and is not particularly limited, and a lithium oxide, a hydroxide, a carbonate, a nitrate, a sulfuric acid. Examples thereof include salts and organic acid salts.
• Cobalt compound according to the raw material mixing step is not particularly limited, as long as it is a cobalt compound used as a raw material for producing a lithium cobalt-based composite oxide, cobalt oxide, oxyhydroxide, hydroxide, Examples thereof include carbonates, nitrates, sulfates and organic acid salts.
• the titanium compound relating to the raw material mixing step is not particularly limited as long as it is a titanium compound used as a raw material for producing a lithium cobalt composite oxide to which an element of titanium is added, and is not particularly limited, and an oxide of titanium, a hydroxide. , Carbonates, nitrates, sulfates, organic acid salts and the like. Of these, titanium dioxide is preferable as the titanium compound.
• the mixing ratio of the lithium compound and the cobalt compound is such that the molar ratio of lithium atoms to the molar number of cobalt atoms (Li / Co mixed molar ratio) is preferably 0.90 to 1.20, particularly preferably 0.
• the mixing ratio is from 0.95 to 1.15.
• the mixing ratio of the titanium compound is preferably 0.05 to 2.0 mol% and particularly preferably 0.1 to 1.5 mol% in terms of titanium atom with respect to cobalt atom. Is.
• the mixing ratio of the titanium compound is within the above range, the effect of improving performance such as cycle characteristics, average operating voltage characteristics, energy density retention rate, etc. is enhanced without impairing the original charge / discharge capacity of the lithium cobalt composite oxide. .
• a compound containing an M element can be mixed with the raw material mixture.
• Examples of the compound containing the M element include oxides, hydroxides, carbonates, nitrates and organic acid salts containing the M element.
• a compound containing two or more kinds of the M element may be used, or a compound containing the Ti element such as strontium titanate and the M element may be used.
• the raw material lithium compound, cobalt compound, Ti-containing compound, and M-element-containing compound may be produced in any production history, but may be used in order to produce high-purity titanium-containing lithium-cobalt composite oxide particles. It is preferable that the content of impurities is as small as possible.
• the raw material mixing step as a method of mixing the lithium compound, the cobalt compound, the titanium compound, and the compound containing the M element used as needed, for example, a ribbon mixer, a Henschel mixer, a super mixer, and Now A mixing method using a tar mixer or the like can be mentioned. At the laboratory level, a household mixer is sufficient as a mixing method.
• the firing step is a step of obtaining a titanium-containing lithium cobalt composite oxide by firing the raw material mixture obtained by performing the raw material mixing step.
• the firing temperature for firing the raw material mixture and reacting the raw materials is 800 to 1150 ° C, preferably 900 to 1100 ° C.
• the firing temperature is within the above range, it is possible to reduce the production of unreacted cobalt oxide or overheat decomposition product of the lithium-cobalt composite oxide, which causes the capacity reduction of the titanium-containing lithium-cobalt composite oxide.
• the firing time in the firing step is 1 to 30 hours, preferably 5 to 20 hours.
• the firing atmosphere in the firing step is an oxidizing atmosphere such as air or oxygen gas.
• the titanium-containing lithium-cobalt composite oxide thus obtained may be subjected to a plurality of firing steps if necessary.
• the inorganic fluoride particles relating to the positive electrode active material for a lithium secondary battery of the present invention are insoluble or sparingly soluble in water.
• the inorganic fluoride include MgF 2 , AlF 3 , TiF 4 , ZrF 4 , CaF 2 , BaF 2 , SrF 2 , ZnF 2 and LiF.
• MgF 2 and / or AlF 3 are preferable.
• the inorganic fluoride particles may be used alone or in combination of two or more.
• Inorganic foot particles are granular inorganic fluoride.
• the average particle size of the inorganic fluoride particles is an average particle size determined by a laser diffraction / scattering method, and is preferably 0.01 to 30 ⁇ m, particularly preferably 0.1 to 20 ⁇ m. Since the average particle diameter of the inorganic fluoride particles is in the above range, it is difficult for problems to occur in the kneading step when preparing the positive electrode mixture or in the coating step of applying the obtained positive electrode mixture to the positive electrode current collector. Become.
• the content of the inorganic fluoride particles is preferably 0.05 to 5.0 mol%, particularly preferably 0.1 to 2. mol% in terms of F atom with respect to the Co atom in the titanium-containing lithium cobalt composite oxide particles. 0 mol%.
• the content of the inorganic fluoride particles is within the above range, the effect of improving the cycle characteristics at high voltage is enhanced while suppressing the decrease in charge / discharge capacity of the titanium-containing lithium cobalt composite oxide.
• the ratio of Co atoms in the titanium-containing lithium cobalt composite oxide particles is 2
• the total amount of F atoms in terms of F atoms of the inorganic fluoride particles of at least one kind is adjusted to preferably 0.05 to 5.0 mol%, particularly preferably 0.1 to 2.0 mol%.
• the total content of F atoms in terms of F atoms of the two or more kinds of inorganic fluoride particles is within the above range, so that the titanium-containing lithium cobalt composite is obtained.
• the effect of improving the characteristics such as the cycle characteristics at high voltage, the characteristics of the average operating voltage, the energy density retention rate, etc. is enhanced while suppressing the decrease in the charge / discharge capacity of the oxide.
• the inorganic fluoride particles may be present on the particle surface of the titanium-containing lithium cobalt composite oxide particles, and are simply mixed with the titanium-containing lithium cobalt composite oxide particles. May exist, or both of them may exist. That is, the positive electrode active material for a lithium secondary battery of the present invention comprises titanium-containing lithium cobalt composite oxide particles, and inorganic fluoride particles present on the surface of the titanium-containing lithium cobalt composite oxide particles. Alternatively, it may be a simple mixture of titanium-containing lithium cobalt composite oxide particles and inorganic fluoride particles, or a mixture of both forms.
• the inorganic fluoride particles When the inorganic fluoride particles are present on the particle surface of the titanium-containing lithium cobalt composite oxide particles, the inorganic fluoride particles may be partially present on the titanium-containing lithium cobalt composite oxide particle surface. It is preferable in that the insertion and removal of lithium on the surface of the titanium-containing lithium cobalt composite oxide is not hindered.
• the positive electrode active material for a lithium secondary battery of the present invention is preferably prepared by a production method having a first step of mixing titanium-containing lithium cobalt composite oxide particles shown below and inorganic fluoride particles in a predetermined amount. Manufactured.
• the method for producing a positive electrode active material for a lithium secondary battery of the present invention is a titanium-containing lithium cobalt composite oxide particle and an inorganic fluoride particle are mixed and treated, and the titanium-containing lithium cobalt composite oxide particle and the inorganic fluoride particle.
• the method for producing a positive electrode active material for a lithium secondary battery comprising: a first step of obtaining a mixture of
• the titanium-containing lithium cobalt composite oxide particles according to the first step are the same as the titanium-containing lithium cobalt composite oxide particles according to the positive electrode active material for a lithium secondary battery of the present invention. That is, the titanium-containing lithium-cobalt composite oxide according to the first step is a composite oxide containing lithium, cobalt, and titanium, or any one or more of lithium, cobalt, titanium, and M element. It is a composite oxide containing and.
• the inorganic fluoride particles according to the first step are the same as the inorganic fluoride particles according to the positive electrode active material for a lithium secondary battery of the present invention.
• the mixing process can be performed either dry or wet.
• the device used for dry mixing is not particularly limited as long as a uniform mixture can be obtained, for example, a high speed mixer, a super mixer, a turbosphere mixer, an Eyrich mixer, a Henschel mixer, a Nauter mixer, a ribbon. Blenders, V-type mixers, conical blenders, jet mills, cosmizers, paint shakers, bead mills, ball mills and the like can be mentioned. At the laboratory level, a household mixer is sufficient.
• the dry mixing treatment can be performed in the presence of a small amount of water.
• the mixing state of the titanium-containing lithium cobalt composite oxide particles and the inorganic fluoride particles is more uniform than when performing the dry mixing treatment in the absence of any water. It becomes easy to become.
• the first step when a dry mixing treatment is carried out in the presence of a small amount of water, it is necessary to dry the mixture after the mixing treatment and to carry out the second step of heat-treating the obtained mixture to sufficiently remove water. It is preferable in that the deterioration of characteristics such as the decrease of discharge capacity and the deterioration of cycle characteristics hardly occurs.
• the amount of water added is preferably 1 to 10% by mass based on the mixture of titanium-containing lithium cobalt composite oxide particles and inorganic fluoride particles. And particularly preferably 2 to 5% by mass.
• the dry mixing treatment is carried out in the presence of water in the first step, it is preferable to carry out the second step of drying the mixture at 80 to 200 ° C. and then heat treating the obtained mixture after the mixing treatment.
• titanium-containing lithium cobalt composite oxide particles and inorganic fluoride particles are added to a water solvent in a solid content of 10 to 80% by mass, preferably 20 to 70% by mass is added, and this is mixed by mechanical means to prepare a slurry, and then the slurry is dried in a state where it is allowed to stand, or alternatively, the slurry is spray-dried and dried. And the like to obtain a mixture of lithium cobalt composite oxide particles and inorganic fluoride particles.
• the apparatus used for wet mixing is not particularly limited as long as it can obtain a uniform slurry.
• Equipment such as a mill, an attritor and a powerful stirrer can be mentioned.
• the wet mixing process is not limited to the mixing process by the mechanical means exemplified above.
• a surfactant may be added to the slurry to carry out the mixing process.
• the dry mixing treatment when the dry mixing treatment is performed in the presence of a small amount of water or when the wet mixing treatment is performed, it is necessary to perform the second step after the first step to reduce the charge / discharge capacity due to moisture or the cycle. It is preferable in that it is possible to make it difficult to cause deterioration of characteristics such as deterioration of characteristics.
• the mixture of the titanium-containing lithium cobalt composite oxide particles and the inorganic fluoride particles obtained in the first step is heat-treated.
• the temperature of the heat treatment in the second step is preferably 200 to 1100 ° C, particularly preferably 500 to 1000 ° C. When the temperature of the heat treatment is within the above range, moisture can be sufficiently removed, and it is possible to prevent the deterioration of characteristics such as decrease of charge / discharge capacity and deterioration of cycle characteristics.
• the heat treatment time in the second step is preferably 1 to 10 hours, particularly preferably 2 to 7 hours.
• the atmosphere for the heat treatment in the second step is preferably an oxidizing atmosphere such as air or oxygen gas.
• the lithium secondary battery of the present invention uses the positive electrode active material for a lithium secondary battery of the present invention as the positive electrode active material.
• the lithium secondary battery of the present invention comprises a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte containing a lithium salt.
• the positive electrode of the lithium secondary battery of the present invention is formed, for example, by applying a positive electrode mixture on a positive electrode current collector and drying.
• the positive electrode mixture is composed of a positive electrode active material, a conductive agent, a binder, and a filler added if necessary.
• the positive electrode active material for a lithium secondary battery of the present invention is uniformly applied to the positive electrode. For this reason, the lithium secondary battery of the present invention has high battery performance, particularly excellent cycle characteristics, maintains a high reduction in average operating voltage, and maintains a high energy density retention rate.
• the content of the positive electrode active material contained in the positive electrode mixture for the lithium secondary battery of the present invention is 70 to 100% by mass, preferably 90 to 98% by mass.
• the positive electrode current collector for the lithium secondary battery of the present invention is not particularly limited as long as it is an electron conductor that does not undergo a chemical change in the constructed battery, and examples thereof include stainless steel, nickel, aluminum and titanium. Examples include fired carbon, aluminum and stainless steel whose surfaces are surface-treated with carbon, nickel, titanium and silver. The surface of these materials may be oxidized and used, or the surface of the current collector may be made uneven by surface treatment. Examples of the form of the current collector include a foil, a film, a sheet, a net, a punched product, a lath body, a porous body, a foam body, a fiber group, and a non-woven fabric molded body. The thickness of the current collector is not particularly limited, but is preferably 1 to 500 ⁇ m.
• the conductive agent for the lithium secondary battery of the present invention is not particularly limited as long as it is an electron conductive material that does not cause a chemical change in the constructed battery.
• graphite such as natural graphite and artificial graphite, carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, carbon black such as thermal black, conductive fibers such as carbon fiber and metal fiber, Fluorinated carbon, aluminum, metal powders such as nickel powder, conductive whiskers such as zinc oxide and potassium titanate, conductive metal oxides such as titanium oxide, or conductive materials such as polyphenylene derivatives.
• Examples of graphite include scaly graphite, scaly graphite, and earthy graphite. These can be used alone or in combination of two or more.
• the mixing ratio of the conductive agent in the positive electrode mixture is 1 to 50% by mass, preferably 2 to 30% by mass.
• binder for the lithium secondary battery of the present invention examples include starch, polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, regenerated cellulose, diacetyl cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene.
• Ethylene-propylene-diene terpolymer EPDM
• sulfonated EPDM styrene-butadiene rubber
• fluororubber tetrafluoroethylene-hexafluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perm Fluoroalkyl vinyl ether copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene Copolymer, ethylene-tetrafluoroethylene copolymer, polychlorotrifluoroethylene, vinylidene fluoride-pentafluoropropylene copolymer, propylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer, fluorine Vinylidene fluoride-hexa
• the compounding ratio of the binder is 1 to 50% by mass, preferably 5 to 15% by mass in the positive electrode mixture.
• the filler for the lithium secondary battery of the present invention suppresses volume expansion of the positive electrode in the positive electrode mixture, and is added as necessary.
• any fibrous material that does not cause a chemical change in the constructed battery can be used.
• olefin polymers such as polypropylene and polyethylene, fibers such as glass and carbon are used.
• the amount of the filler added is not particularly limited, but is preferably 0 to 30% by mass in the positive electrode mixture.
• the negative electrode of the lithium secondary battery of the present invention is formed by applying a negative electrode material on the negative electrode current collector and drying it.
• the negative electrode current collector according to the lithium secondary battery of the present invention is not particularly limited as long as it is an electron conductor that does not undergo a chemical change in the constructed battery, and examples thereof include stainless steel, nickel, copper and titanium. , Aluminum, calcined carbon, copper or stainless steel whose surface is treated with carbon, nickel, titanium, silver, and an aluminum-cadmium alloy. Further, the surface of these materials may be used after being oxidized, or the surface of the current collector may be made uneven by surface treatment.
• Examples of the form of the current collector include a foil, a film, a sheet, a net, a punched product, a lath body, a porous body, a foam body, a fiber group, and a non-woven fabric molded body.
• the thickness of the current collector is not particularly limited, but is preferably 1 to 500 ⁇ m.
• the negative electrode material for the lithium secondary battery of the present invention is not particularly limited, and examples thereof include carbonaceous materials, metal composite oxides, lithium metals, lithium alloys, silicon alloys, tin alloys, and metal oxides. Materials, conductive polymers, chalcogen compounds, Li—Co—Ni-based materials, Li 4 Ti 5 O 12 , lithium niobate, silicon oxide (SiOx: 0.5 ⁇ x ⁇ 1.6) and the like. Examples of carbonaceous materials include non-graphitizable carbon materials and graphite-based carbon materials.
• Examples of the metal composite oxide include Sn p (M 1 ) 1 -p (M 2 ) q O r (wherein, M 1 represents one or more elements selected from Mn, Fe, Pb and Ge, M 2 represents one or more kinds of elements selected from Al, B, P, Si, Group 1, Group 2, Group 3 and halogen elements of the periodic table, and 0 ⁇ p ⁇ 1, 1 ⁇ q ⁇ 3 1 ⁇ r ⁇ 8), Li t Fe 2 O 3 (0 ⁇ t ⁇ 1), Li t WO 2 (0 ⁇ t ⁇ 1), and the like.
• Examples of the metal oxide include GeO, GeO 2 , SnO, SnO 2 , PbO, PbO 2 , Pb 2 O 3 , Pb 3 O 4 , Sb 2 O 3 , Sb 2 O 4 , Sb 2 O 5 , Bi 2 O 3. , Bi 2 O 4 , Bi 2 O 5 and the like.
• Examples of the conductive polymer include polyacetylene and poly-p-phenylene.
• an insulating thin film having a large ion permeability and a predetermined mechanical strength is used as the separator for the lithium secondary battery of the present invention.
• a sheet or non-woven fabric made of an olefin polymer such as polypropylene or glass fiber or polyethylene is used because of its resistance to organic solvents and hydrophobicity.
• the pore size of the separator may be in a range generally useful for batteries, and is, for example, 0.01 to 10 ⁇ m.
• the thickness of the separator may be in the range for general batteries, and is, for example, 5 to 300 ⁇ m.
• the solid electrolyte such as a polymer is used as the electrolyte described below, the solid electrolyte may also serve as the separator.
• the non-aqueous electrolyte containing the lithium salt according to the lithium secondary battery of the present invention is composed of the non-aqueous electrolyte and the lithium salt.
• a non-aqueous electrolytic solution As the non-aqueous electrolyte relating to the lithium secondary battery of the present invention, a non-aqueous electrolytic solution, an organic solid electrolyte, or an inorganic solid electrolyte is used.
• the non-aqueous electrolytic solution include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ⁇ -butyrolactone, 1,2-dimethoxyethane, tetrahydroxyfuran and 2-methyl.
• aprotic organic solvents such as ethyl propionate.
• Examples of the organic solid electrolyte relating to the lithium secondary battery of the present invention include polyethylene derivatives, polyethylene oxide derivatives or polymers containing them, polypropylene oxide derivatives or polymers containing them, phosphate ester polymers, polyphosphazenes, polyaziridines, polyethylenes.
• Examples thereof include polymers having an ionic dissociative group such as sulfide, polyvinyl alcohol, polyvinylidene fluoride, and polyhexafluoropropylene, and a mixture of the polymer having an ionic dissociative group and the above nonaqueous electrolytic solution.
• Li nitride, halide, oxyacid salt, sulfide and the like can be used, and for example, Li 3 N, LiI, Li 5 NI 2 , Li 3 N-LiI-LiOH, LiSiO 4 , LiSiO 4 -LiI-LiOH, Li 2 SiS 3 , Li 4 SiO 4 , Li 4 SiO 4 -LiI-LiOH, P 2 S 5 , Li 2 S or Li 2 SP 2 S 5 , Li 2 S-SiS 2 , Li 2 S-GeS 2 , Li 2 S-Ga 2 S 3 , Li 2 S-B 2 S 3 , Li 2 S-P 2 S 5 -X, Li 2 S --SiS 2 --X, Li 2 S--GeS 2 --X, Li 2 S--Ga 2 S 3 --X, Li 2 S--B 2 S 3 --X, (wherein
• the inorganic solid electrolyte is amorphous (glass), lithium phosphate (Li 3 PO 4 ), lithium oxide (Li 2 O), lithium sulfate (Li 2 SO 4 ), phosphorus oxide (P 2 O 5).
• a compound containing oxygen such as lithium borate (Li 3 BO 3 ), Li 3 PO 4-u N 2u / 3 (u is 0 ⁇ u ⁇ 4), Li 4 SiO 4-u N 2u / 3 (u is Nitrogen such as 0 ⁇ u ⁇ 4), Li 4 GeO 4-u N 2u / 3 (u is 0 ⁇ u ⁇ 4), Li 3 BO 3-u N 2u / 3 (u is 0 ⁇ u ⁇ 3)
• the compound containing can be contained in the inorganic solid electrolyte.
• lithium salt relating to the lithium secondary battery of the present invention those which are dissolved in the above non-aqueous electrolyte are used, and for example, LiCl, LiBr, LiI, LiClO 4 , LiBF 4 , LiB 10 Cl 10 , LiPF 6 , LiCF 3 are used.
• the following compounds can be added to the non-aqueous electrolyte for the purpose of improving discharge, charging characteristics and flame retardancy.
• pyridine triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivative, sulfur, quinoneimine dye, N-substituted oxazolidinone and N, N-substituted imidazolidine, ethylene glycol dialkyl ether.
• a halogen-containing solvent such as carbon tetrachloride or ethylene trifluoride can be contained in the electrolytic solution.
• the electrolytic solution may contain carbon dioxide gas in order to have suitability for high temperature storage.
• the lithium secondary battery of the present invention is a lithium secondary battery having a high capacity per volume, excellent safety, cycle characteristics and operating voltage, and the shape of the battery is a button, a sheet, a cylinder, a corner, a coin type, etc. It may have any shape.
• the application of the lithium secondary battery of the present invention is not particularly limited, and examples thereof include laptop computers, laptop computers, pocket word processors, mobile phones, cordless handsets, portable CD players, radios, LCD TVs, backup power supplies, electric shavers, Examples include electronic devices such as memory cards and video movies, and consumer electronic devices such as automobiles, electric vehicles, game machines, and electric tools.
• ⁇ LCO particles 1a> Weigh lithium carbonate (average particle size 5.7 ⁇ m), tricobalt tetraoxide (average particle size 2.5 ⁇ m), titanium dioxide (average particle size 0.4 ⁇ m) and calcium sulfate (average particle size 7.3 ⁇ m). After sufficiently mixing with a household mixer, a raw material mixture having a Li / Co molar ratio of 1.04, a Ti / Co molar ratio of 0.01, and a Ca / Co molar ratio of 0.0006 was obtained. Next, the obtained raw material mixture was baked in an alumina pot at 1050 ° C. for 5 hours in the air. After firing, the fired product was crushed and classified to obtain lithium cobalt composite oxide particles containing 1.0 mol% of Ti and 0.06 mol% of Ca with respect to Co.
• ⁇ LCO particles 1b> Weigh lithium carbonate (average particle size 5.7 ⁇ m), tricobalt tetraoxide (average particle size 3.3 ⁇ m), titanium dioxide (average particle size 0.4 ⁇ m) and calcium sulfate (average particle size 7.3 ⁇ m). After sufficiently mixing with a household mixer, a raw material mixture having a Li / Co molar ratio of 1.04, a Ti / Co molar ratio of 0.01, and a Ca / Co molar ratio of 0.0006 was obtained. Next, the obtained raw material mixture was baked in an alumina pot at 1050 ° C. for 5 hours in the air. After firing, the fired product was crushed and classified to obtain lithium cobalt composite oxide particles containing 1.0 mol% of Ti and 0.06 mol% of Ca with respect to Co.
• the ratio is 1.05, the Ti / Co molar ratio is 0.00175, the Sr / Co molar ratio is 0.00125, the Mg / Co molar ratio is 0.00125, and the Zr / Co molar ratio is 0.00125.
• a raw material mixture having an Al / Co molar ratio of 0.008 was obtained. Then, the obtained raw material mixture was fired in an alumina pot at 1080 ° C. for 5 hours in the atmosphere. After firing, the fired product is crushed and classified to have Ti of 0.175 mol%, Mg of 0.125 mol%, Sr of 0.125 mol%, and Zr of 0.125 mol% with respect to Co. Lithium cobalt composite oxide particles containing 0.8 mol% of Al were obtained.
• the physical properties of the lithium-cobalt composite oxide sample (LCO sample) obtained above are shown in Table 1.
• the average particle size was determined by the laser diffraction / scattering method.
• Inorganic fluoride particles Commercially available inorganic fluoride particles were pulverized as the inorganic fluoride particles, and the inorganic fluoride particles having the physical properties shown in Table 2 below were used.
• Examples 1 to 9 Using LCO particles 1a or 1b described in Table 1, LCO particles 1a or 2b and the above-mentioned MgF 2 , AlF 3 were weighed so that the inorganic fluoride particles had the addition amount shown in the first step of Table 3, Mix well with a mixing mixer. Then, the mixture was subjected to heat treatment (at 600 ° C. for 5 hours) shown in the second step of Table 3 in the atmosphere to prepare a positive electrode active material sample.
• Example 10 Using the LCO particles 1b described in Table 1, the LCO particles 1b and the above MgF 2 and AlF 3 were weighed so that the inorganic fluoride particles had the addition amounts shown in the first step of Table 3, and water was further added. A 40 mass% slurry was prepared and thoroughly mixed with a stirrer. Then, the slurry was spray-dried with a spray dryer adjusted to an exhaust air temperature of 120 ° C. to obtain a dry powder. Then, the dry powder was subjected to a heat treatment (at 600 ° C. for 5 hours) shown in the second step of Table 3 in the atmosphere to prepare a positive electrode active material sample.
• a heat treatment at 600 ° C. for 5 hours
• Example 11 Using LCO particles 2 shown in Table 1, LCO particles 1a or 2b and the above-mentioned MgF 2 and AlF 3 were weighed so that the inorganic fluoride particles had the addition amount shown in the first step of Table 3, and a household mixer was used. And mixed well. Then, the mixture was subjected to heat treatment (at 600 ° C. for 5 hours) shown in the second step of Table 3 in the atmosphere to prepare a positive electrode active material sample.
• Example 12 Using LCO particles 2 described in Table 1, LCO particles 2 and the above MgF 2 and AlF 3 were weighed so that the inorganic fluoride particles had the addition amounts shown in the first step of Table 3, and water was further added. A 32 mass% slurry was prepared and sufficiently stirred and mixed with a stirrer. Then, the slurry was spray-dried with a spray dryer adjusted to an exhaust air temperature of 120 ° C. to obtain a dry powder. Then, the dry powder was subjected to a heat treatment (at 600 ° C. for 5 hours) shown in the second step of Table 3 in the atmosphere to prepare a positive electrode active material sample.
• a heat treatment at 600 ° C. for 5 hours
• the added amount of the inorganic fluoride particles was expressed in mol% as the F atom amount in terms of F atom with respect to the Co atom in the lithium cobalt composite oxide particles.
• a battery performance test was conducted as follows. ⁇ Preparation of lithium secondary battery> 95% by mass of the positive electrode active material obtained in Examples and Comparative Examples, 2.5% by mass of graphite powder, and 2.5% by mass of polyvinylidene fluoride were mixed to obtain a positive electrode agent, which was converted into N-methyl-2-pyrrolidinone. The mixture was dispersed to prepare a kneading paste. The kneading paste was applied to an aluminum foil, dried, pressed and punched into a disk having a diameter of 15 mm to obtain a positive electrode plate.
• a coin-type lithium secondary battery was manufactured by using each member such as a separator, a negative electrode, a positive electrode, a current collecting plate, a fitting, an external terminal, and an electrolytic solution.
• a metal lithium foil was used for the negative electrode, and an electrolyte prepared by dissolving 1 mol of LiPF 6 in 1 liter of a 1: 1 kneading solution of ethylene carbonate and methyl ethyl carbonate was used. Then, the performance evaluation of the obtained lithium secondary battery was performed. The results are shown in Tables 4 to 6.
• Capacity retention rate was calculated by the following formula from the discharge capacity (per active material weight) of each of the first cycle and the 20th cycle in the cycle characteristic evaluation.
• Capacity retention rate (%) (20th cycle discharge capacity / 1st cycle discharge capacity) x 100 (4)
• Initial average operating voltage The average operating voltage at the time of discharging in the first cycle in the cycle characteristic evaluation was defined as the initial average operating voltage.
• Average Operating Voltage Reduction Amount The average operating voltage reduction ( ⁇ V) was calculated by the following formula from the average operating voltage at the time of discharging in each of the first cycle and the 20th cycle in the cycle characteristic evaluation.
• Average operating voltage decrease amount (V) average operating voltage at 1st cycle ⁇ average operating voltage at 20th cycle (6)
• Energy density maintenance rate (%) (Discharge Wh capacity at 20th cycle / Discharge Wh capacity at 1st cycle) ⁇ 100
• the average operating voltage at the 20th cycle was increased by 0.02 V as compared with the average operating voltage at the first time.
• the average operating voltage at the 20th cycle was increased by 0.04V as compared with the average operating voltage at the first time.

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