WO2013129423A1 - Lithium titanate particulate powder, negative electrode active material particulate powder for non-aqueous electrolyte secondary battery, and non-aqueous electrolyte secondary battery - Google Patents

Lithium titanate particulate powder, negative electrode active material particulate powder for non-aqueous electrolyte secondary battery, and non-aqueous electrolyte secondary battery Download PDF

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WO2013129423A1
WO2013129423A1 PCT/JP2013/055013 JP2013055013W WO2013129423A1 WO 2013129423 A1 WO2013129423 A1 WO 2013129423A1 JP 2013055013 W JP2013055013 W JP 2013055013W WO 2013129423 A1 WO2013129423 A1 WO 2013129423A1
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lithium titanate
particle powder
active material
lithium
secondary battery
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French (fr)
Japanese (ja)
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藤田　和也
一路 古賀
亮尚 梶山
森　幸治
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戸田工業株式会社
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G23/00—Compounds of titanium
    • C01G23/003—Titanates
    • C01G23/005—Alkali titanates
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/30—Three-dimensional structures
    • C01P2002/32—Three-dimensional structures spinel-type (AB2O4)
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
    • C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/64—Nanometer sized, i.e. from 1-100 nanometer
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/12—Surface area
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/40—Electric properties
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present invention relates to a lithium titanate particle powder that exhibits excellent initial discharge capacity and excellent gas generation suppression as a negative electrode active material for a non-aqueous electrolyte secondary battery, and a non-aqueous electrolyte using the material as a negative electrode active material A secondary battery is provided.
  • lithium titanate As a negative electrode active material.
  • Lithium titanate Li 4 Ti 5 O 12 is known as a highly reliable negative electrode active material with high structural stability because the crystal structure change in the lithium ion insertion / extraction reaction due to charge / discharge is very small. .
  • Li 4 Ti 5 O 12 As a manufacturing method for obtaining lithium titanate (Li 4 Ti 5 O 12 ), a mixed powder in which a lithium salt and a titanium oxide are dry or wet mixed so that a Li / Ti ratio is approximately 0.80.
  • a so-called solid phase reaction method (hereinafter referred to as a dry method) is known in which Li 4 Ti 5 O 12 is obtained by heating and baking (these are simply a mixture of a lithium salt and a titanium oxide) (patented) References 1, 2).
  • a liquid phase reaction + solid phase reaction method (hereinafter referred to as a wet method) is known, in which a mixture of titanium and lithium is hydrothermally treated and then heated and fired to obtain Li 4 Ti 5 O 12 (Patent Patent) References 3, 4).
  • lithium titanate particle powder made of Li 4 Ti 5 O 12 with high purity by reducing the impurity phase is used, a negative electrode active material having a high initial discharge capacity, excellent output characteristics, and capable of suppressing gas generation has not yet been obtained. It is not done. In particular, in a laminate type cell, contact failure occurs due to gas generation, and battery characteristics deteriorate. Therefore, lithium titanate that generates extremely little gas is desired.
  • the inventors of the present invention focused on the abundance of TiO 2 and Li 2 TiO 3 contained in the target product Li 4 Ti 5 O 12, and as a result of earnest and examination, as a result of the conventional knowledge, that is, Li 4 Ti Rather than increasing the purity of 5 O 12 , both Li 2 TiO 3 is present in a specific range, and the specific surface area by the BET method is adjusted to a specific range, so both initial discharge capacity and gas generation suppression are excellent. It was also found that the negative electrode active material can be obtained. Furthermore, the inventors have found that a negative electrode active material excellent in output characteristics can be obtained by making the crystal distortion below a specific range, and the present invention has been achieved.
  • lithium titanate particles having a spinel structure when lithium titanate particles having a spinel structure are indexed with Fd-3m by XRD, the amount of TiO 2 by Rietveld analysis is 1.5% or less, and the amount of Li 2 TiO 3 is In the range of 1% to 6%, the amount of Li 4 Ti 5 O 12 is 94% to 99%, the crystal distortion is 0.0015 or less, and the specific surface area by the BET method is 2 m 2 / g to 7 m 2.
  • Lithium titanate particle powder characterized by being in a range of not more than / g (Invention 1).
  • the present invention is the lithium titanate particle powder according to the present invention 1 having a Li / Ti ratio (molar ratio) in the range of 0.801 to 0.83 (present invention 2).
  • the present invention is a negative electrode active material particle powder comprising the lithium titanate particle powder according to the present invention 1 or the present invention 2 (Invention 3).
  • the initial discharge capacity is 165 mAh / g or more when the direction in which lithium is inserted is charged.
  • the present invention is a non-aqueous electrolyte secondary battery using the negative electrode active material particle powder according to the present invention 3 or 4 (invention 5).
  • the lithium titanate particle powder according to the present invention exhibits excellent initial discharge capacity and output characteristics when used in a non-aqueous electrolyte secondary battery as a negative electrode active material particle powder, and has a balance in which gas generation is suppressed. Since good battery characteristics are obtained, it is suitable as an active material particle powder for a non-aqueous electrolyte secondary battery.
  • FIG. 2 is an XRD pattern of lithium titanate particle powder obtained in Example 1.
  • FIG. 2 is a scanning electron micrograph of lithium titanate particle powder obtained in Example 2.
  • the lithium titanate particle powder according to the present invention has at least a spinel structure, is a compound that can be expressed as Li 4 Ti 5 O 12 in a general chemical formula, and contains at least Li 2 TiO 3 .
  • the presence state of Li 2 TiO 3 in the lithium titanate particle powder according to the present invention may be in a state of being coated on the particle surface or in an island shape as long as it is in an amount specified by the present invention, Any shape may be present in the grains.
  • diffraction between 10 to 90 degrees (2 ⁇ / ⁇ ) can be indexed with Fd-3m in XRD.
  • Fd-3m XRD
  • the abundance of TiO 2 is 1.5% or less, and the abundance of Li 2 TiO 3 is in the range of 1.0 to 6.0%.
  • the abundance of TiO 2 exceeds 1.5%, the output characteristics are deteriorated.
  • the abundance of Li 2 TiO 3 is less than 1.0%, the initial discharge capacity and output characteristics of the secondary battery produced using this lithium titanate particle powder as the negative electrode active material particle powder are good, but the gas Occurrence increases.
  • the abundance of TiO 2 is 1.0% or less, the abundance of Li 2 TiO 3 is 1.5 to 5.0%, more preferably the abundance of TiO 2 is 0.5% or less.
  • the abundance of Li 2 TiO 3 is 2.0 to 4.0%.
  • BET specific surface area of the lithium titanate particles according to the present invention is in the range of less 2m 2 / g or more 7m 2 / g. If the specific surface area is smaller than this range, the battery capacity becomes small and the practicality is lacking. If it is larger than this range, gas is likely to be generated and the battery swells significantly.
  • the lithium titanate particle powder is subjected to XRD measurement, and the crystal distortion of the lithium titanate particle powder can be obtained by Rietveld analysis.
  • the XRD measurement condition was 2 ⁇ / ⁇ , and a range of 10 to 90 degrees was scanned 0.02 degrees.
  • the range of crystal distortion in the present invention is suitable.
  • the crystal strain exceeds 0.0015, the output characteristics deteriorate.
  • a preferable range of crystal distortion is 0.0014 or less, and a more preferable range is 0.0001 to 0.0013.
  • the following effects are brought about by satisfying the conditions defined in the present invention by various characteristics such as Li 2 TiO 3 abundance, specific surface area and crystal distortion of the lithium titanate particle powder. Conceivable.
  • an active material can suppress gas generation due to its small specific surface area.
  • the specific surface area is too small, the initial capacity is also reduced.
  • the present inventors have found that it is also related to the amount of Li 2 TiO 3 in the lithium titanate powder. Although this effect is not clear, when Li 2 TiO 3 is present in the lithium titanate particles or in the surface layer, when lithium titanate becomes Li 7 Ti 5 O 12 by full charge, not Li The existence point of 2 TiO 3 remains, and as a result, gas generation is considered to be small.
  • a prescription for increasing the specific surface area for example, a method for making fine particles
  • damage to the particles occurs when making fine particles.
  • distortion remains in the particles. It has been found that when this distortion is larger than the range of the present invention, the output characteristics deteriorate rapidly.
  • Li 2 TiO 3 abundance, specific surface area, and crystal distortion of the lithium titanate particle powder within a specific range a balance can be obtained when used as an active material particle powder for a non-aqueous electrolyte secondary battery. Battery characteristics can be obtained.
  • the Li / Ti ratio (molar ratio) of the lithium titanate particles according to the present invention is preferably 0.801 to 0.83.
  • a more preferable Li / Ti ratio (molar ratio) is 0.803 to 0.828, more preferably 0.805 to 0.827, and still more preferably 0.807 to 0.826.
  • the production method of the lithium titanate particle powder according to the present invention is not particularly limited, and can be synthesized by a method such as a wet method / dry method.
  • lithium titanate particle powder is produced by a dry method.
  • lithium titanate particle powder is obtained.
  • the lithium compounds that can be used in the present invention include lithium carbonate, lithium hydroxide, lithium acetate, lithium nitrate, and lithium oxide, but inexpensive lithium carbonate is preferable.
  • TiO 2 used in the present invention is not particularly limited, water hydrates can also be used.
  • the TiO 2 to be used preferably has a crystallite size of 10 to 100 nm. In the case of TiO 2 hydrate, the thickness is preferably 1 to 20 nm. If it is larger than the crystallite size, a large amount of heterogeneous phase is generated in the synthesis, making it difficult to obtain the target lithium titanate particle powder of the present invention.
  • TiO 2 that can be used in the present invention has an anatase type, a rutile type, and a mixed phase thereof, and an anatase type is preferable.
  • the lithium compound and TiO 2 used for producing the lithium titanate particle powder according to the present invention are preferably adjusted and mixed so that the Li / Ti ratio after firing is 0.801 to 0.83.
  • it can be done by adjusting the mixing ratio of the lithium compound and TiO 2.
  • the reason why Li / Ti is made larger than the theoretical ratio of 0.80 is to obtain lithium titanate having higher crystallinity and to leave Li 2 TiO 3 after firing. If it is larger than the above range, the initial discharge capacity is decreased, and the lithium titanate particles obtained by further increasing the Li 2 TiO 3 residue have a large residual alkali, resulting in gelation of the paint.
  • the mixture is fired at 700 to 900 ° C. to obtain the lithium titanate particle powder according to the present invention. If the firing temperature is less than 700 ° C., a large amount of TiO 2 remains. If the firing temperature is too high, the amount of lithium evaporation increases and a large amount of TiO 2 phase is generated.
  • the firing temperature is preferably 700 to 880 ° C. However, since the progress of the reaction varies depending on the characteristics of the TiO 2 used (BET specific surface area, crystallite diameter, etc.), the preferred temperature range of the firing temperature varies.
  • the atmosphere in firing may be an oxidizing atmosphere or a reducing atmosphere.
  • the lithium titanate particle powder obtained in the present invention may have oxygen deficiency or oxygen excess within the range of known techniques.
  • the particle size distribution can be adjusted by pulverizing the lithium titanate particle powder obtained by firing.
  • the shape of the particle size distribution may be sharp, broad, or bimodal.
  • a ball mill, a bead mill, a hammer mill or the like can be used for pulverization.
  • the target lithium titanate particle powder can be obtained by combining the Li / Ti ratio, firing temperature and firing time, and pulverization conditions of the raw material mixed powder. For example, when heat treatment is performed at a relatively high temperature, a product having a low specific surface area tends to be obtained, and when the pulverization time is increased, crystal strain tends to increase.
  • the lithium titanate particle powder according to the present invention can be used as a negative electrode active material particle powder for a non-aqueous electrolyte secondary battery.
  • a conductive agent and a binder are added and mixed according to a conventional method.
  • the conductive agent acetylene black, carbon black, graphite and the like are preferable
  • the binder polytetrafluoroethylene, polyvinylidene fluoride and the like are preferable.
  • the secondary battery manufactured using the negative electrode containing the negative electrode active material particle powder according to the present invention includes a positive electrode, a negative electrode, and an electrolyte.
  • lithium cobaltate lithium manganate, lithium nickelate or the like, which is a positive electrode material for a general non-aqueous electrolyte secondary battery, can be used.
  • an organic solvent containing at least one of carbonates such as propylene carbonate and dimethyl carbonate and ethers such as dimethoxyethane can be used as the solvent for the electrolytic solution.
  • At least one lithium salt such as lithium perchlorate and lithium tetrafluoroborate can be dissolved in the above solvent and used.
  • the non-aqueous electrolyte secondary battery manufactured using the electrode containing the negative electrode active material particle powder according to the present invention has an initial discharge capacity of 1.0 V or higher by an evaluation method described later of 165 mAh / g or higher.
  • the gas generation amount was 1.0 cc / cm 3 according to the evaluation method described later. Is less than.
  • the lithium titanate particle powder according to the present invention can also be used as a positive electrode active material.
  • the non-aqueous electrolyte secondary battery is composed of the above electrode, counter electrode and electrolyte, and the counter electrode (negative electrode) is metallic lithium, lithium alloy, or graphite. Carbonaceous materials such as coke are used.
  • the most important point in the present invention is the use of a lithium titanate particle powder having a specific surface area and crystal distortion within the range of the present invention, in which a specific amount of Li 2 TiO 3 according to the present invention is present. It is possible to obtain a non-aqueous electrolyte secondary battery that has excellent initial discharge capacity and output characteristics and can suppress gas generation.
  • the impurity phase has been reduced to obtain lithium titanate particle powder made of Li 4 Ti 5 O 12 having high purity.
  • simply making it high purity does not sufficiently satisfy the characteristics that the initial discharge capacity is high and gas generation can be suppressed.
  • the present inventors have quantified the impurity phase by Rietveld analysis, which can be more accurately quantified than the quantification by the peak intensity ratio of X-ray diffraction, the presence of a very small amount of Li 2 TiO 3 , and the BET specific surface area. By controlling the crystal strain, it is possible to obtain a negative electrode active material exhibiting high battery characteristics.
  • a typical embodiment of the present invention is as follows.
  • the BET specific surface area was measured by using a Macsorb HM Model-1208 manufactured by Mountech Co., Ltd. after drying and deaeration of the sample under nitrogen gas at 120 ° C. for 45 minutes.
  • the Li / Ti ratio was determined by preparing an adjustment liquid and quantifying each element using ICAP6500 Thermo Fisher Scientific Co., Ltd. for ICP measurement.
  • the X-ray diffraction of the sample was measured using a SmartLab manufactured by Rigaku Corporation (10 to 90 degrees, 0.02 degree step scan).
  • the amount of TiO 2 and the amount of Li 2 TiO 3 and the calculation of crystal distortion and crystallite size were calculated by performing Rietveld analysis using X-ray diffraction data.
  • Rietan2000 was used for Rietveld analysis.
  • the negative electrode active material particle powder according to the present invention was subjected to battery evaluation using a 2032 type coin cell.
  • lithium titanate which is an active material particle powder for a negative electrode according to the present invention
  • the amount of active material is 90% by weight
  • acetylene black is 2.5% by weight as a conductive material
  • graphite is 2%.
  • 5% by weight and 5% by weight of polyvinylidene fluoride dissolved in N-methylpyrrolidone as a binder were mixed, applied to an Al metal foil, and dried at 120 ° C. The sheet was punched out to 16 mm ⁇ , and then pressure-bonded at 3.0 t / cm 2 was used for the positive electrode.
  • the counter electrode was made of metallic lithium with a thickness of 500 ⁇ m punched to 16 mm ⁇ , and the electrolyte was a 2032 type coin cell using a solution in which EC and DMC in which 1 mol / L LiPF 6 was dissolved was mixed at a volume ratio of 1: 2. .
  • Charging / discharging characteristics were as follows: charging was performed at a current density of 0.1 C up to 1.0 V when charging was performed in a direction where Li was desorbed in an environment of a constant temperature bath at 25 ° C. (CC-CC operation) Thereafter, discharging was performed at a current density of 0.1 C up to 3.0 V (CC-CC operation).
  • the first charge capacity (1st-CH) and discharge capacity (1st-DCH) of this operation were measured. The measurement results are shown in Table 2. In Table 2, when the initial charge capacity was 165 mAh / g or more, “ ⁇ ”, and less than 165 mAh / g, “ ⁇ ”.
  • the output characteristics were as follows: discharging was performed at a current density of 0.1 C up to 1.0 V in a constant temperature bath at 25 ° C. (CC-CC operation), and charging was performed at a current density of 0.1 C up to 3.0 V (CC-CC operation). Let the discharge capacity at this time be a. Next, discharging was performed at a current density of 4 C up to 1.0 V (CC-CC operation), and charging was performed at a current density of 0.1 C up to 3.0 V (CC-CC operation). When the discharge capacity at this time is b, the output characteristic is (b / a ⁇ 100 (%)). The measurement results are shown in Table 2. In Table 2, when the output characteristic is 80 or more, “ ⁇ ” is set, and when the output characteristic is less than 80%, “X” is set.
  • the gas generation amount was evaluated by producing a laminate cell by the following method.
  • Li 1.07 Mn 1.83 Al 0.1 O 4 was 92% by weight, acetylene black was 2.5% by weight as a conductive material, graphite was 2.5% by weight, and dissolved in N-methylpyrrolidone as a binder. 3% by weight of polyvinylidene fluoride was mixed, applied to an Al metal foil, dried at 120 ° C., cut into a 40 mm ⁇ 100 mm square, and then consolidated at 3.0 t / cm 2 . It was.
  • a laminate cell was prepared by combining two sets of these electrodes so as to face each other.
  • the initial charge / discharge was performed at room temperature, and then charged to 2.7 V, and the volume of the laminate cell at this voltage was measured.
  • the volume of the laminate cell was measured again, and the amount of gas generated was evaluated from the volume change before and after high-temperature storage.
  • the measurement results are shown in Table 2.
  • the gas generation amount of 1.0 cc / g or less was designated as “ ⁇ ”, and the gas generation amount exceeding 1.0 cc / g was designated as “x”.
  • Example 1 TiO 2 having a specific surface area of 50 m 2 / g and lithium carbonate were adjusted to a molar ratio of Li / Ti ratio of 0.85, and mixed for 1 hr with Reiki.
  • the mixed powder was put into an alumina crucible and fired in a muffle furnace at a temperature of 850 ° C. for 6 hours in an air atmosphere to obtain lithium titanate particle powder.
  • This lithium titanate was pulverized with a ball mill for 1.5 hours to obtain a lithium titanate powder.
  • Comparative Example 1 Except having changed the molar ratio of Li / Ti ratio into 0.80, it processed similarly to Example 1 and obtained lithium titanate particle powder.
  • Example 2 A lithium titanate particle powder was obtained in the same manner as in Example 1 except that the pulverization time in the ball mill was changed to 3 hours.
  • Comparative Example 2 A lithium titanate particle powder was obtained in the same manner as in Example 1 except that the pulverization time in the ball mill was changed to 6 hours.
  • Example 3 TiO 2 having a specific surface area of 330 m 2 / g and lithium carbonate were adjusted to 0.82 at a molar ratio of Li / Ti ratio, and mixed for 1 hr with Reiki.
  • the mixed powder was put into an alumina crucible and fired in a muffle furnace at a temperature of 750 ° C. for 4 hours in an air atmosphere to obtain lithium titanate particle powder.
  • This lithium titanate was pulverized with a ball mill for 0.5 hours to obtain a lithium titanate powder.
  • Comparative Example 3 A lithium titanate particle powder was obtained in the same manner as in Example 3 except that the molar ratio of Li / Ti ratio was changed to 0.90.
  • Example 4 TiO 2 having a specific surface area of 8 m 2 / g and lithium carbonate were adjusted to a molar ratio of Li / Ti ratio of 1.00, and mixed for 1 hr with Reiki.
  • the mixed powder was put into an alumina crucible and fired in an air atmosphere at a temperature of 880 ° C. for 10 hours in a muffle furnace to obtain lithium titanate particle powder.
  • This lithium titanate was pulverized with a ball mill for 4 hours to obtain a lithium titanate powder.
  • Comparative Example 4 A lithium titanate particle powder was obtained in the same manner as in Example 4 except that the firing temperature was changed to 750 ° C.
  • Example 5 TiO 2 having a specific surface area of 90 m 2 / g and lithium carbonate were adjusted to a molar ratio of Li / Ti ratio of 0.83, and mixed for 1 hr with Reiki.
  • the mixed powder was put into an alumina crucible, and baked in an air atmosphere at a temperature of 840 ° C. for 4 hours in a muffle furnace to obtain lithium titanate particle powder.
  • This lithium titanate was pulverized with a ball mill for 1.5 hours to obtain a lithium titanate powder.
  • Comparative Example 5 A lithium titanate particle powder was obtained in the same manner as in Example 5 except that the pulverization time in the ball mill was changed to 5 hours.
  • Example 6 TiO 2 having a specific surface area of 285 m 2 / g and lithium carbonate were adjusted to a molar ratio of Li / Ti ratio of 0.83, and mixed for 1 hr by Reiki.
  • the mixed powder was put into an alumina crucible and fired in an air atmosphere at a temperature of 800 ° C. for 3 hours in a muffle furnace to obtain lithium titanate particle powder.
  • This lithium titanate was pulverized with a ball mill for 1.5 hours to obtain a lithium titanate powder.
  • Comparative Example 6 A lithium titanate particle powder was obtained in the same manner as in Example 6 except that the firing temperature was changed to 850 ° C. and the firing time was changed to 4 hours. In Comparative Example 6, since the raw material TiO2 had a large BET specific surface area of 285 m 2 / g, the reaction was likely to proceed. By baking at 850 ° C., a low BET specific surface area was obtained.
  • Comparative Example 7 Except having changed the molar ratio of Li / Ti ratio into 0.82, it processed like Example 5 and obtained lithium titanate particle powder.
  • Tables 1 and 2 show characteristics and conditions of lithium titanate obtained in Examples and Comparative Examples.
  • the lithium titanate particle powder according to the present invention has an initial discharge capacity of 165 mAh / g or more and an output characteristic of 80% or more, and gas generation is suppressed to 1.0 cc / g or less. Therefore, it is suitable as an active material for a non-aqueous electrolyte secondary battery.
  • the lithium titanate particle powder according to the present invention exhibits excellent initial discharge capacity and output characteristics when used in a non-aqueous electrolyte secondary battery as a negative electrode active material particle powder, and has a balance in which gas generation is suppressed. Since good battery characteristics are obtained, it is suitable as an active material particle powder for a non-aqueous electrolyte secondary battery.

Abstract

Provided is a lithium titanate particulate powder that has a high initial discharge capacity as an active material for a non-aqueous electrolyte secondary battery, that is capable of minimizing the generation of gas, and that yields well-balanced battery characteristics. The lithium titanate particulate powder of the present invention has a spinel structure, and when an index is applied by Fd-3m in XRD, the TiO2 volume by Reitveld analysis is 1.5% or less, the Li2TiO3 volume is in the range of 1-6%, the Li4Ti5O12 volume is 94-99%, crystal distortion is 0.0015 or less, and the BET specific surface area is in the range of 2-7 m2/g.

Description

チタン酸リチウム粒子粉末、非水電解質二次電池用負極活物質粒子粉末並びに非水電解質二次電池Lithium titanate particle powder, negative electrode active material particle powder for non-aqueous electrolyte secondary battery, and non-aqueous electrolyte secondary battery
　本発明は、非水電解質二次電池用負極活物質として、優れた初期放電容量を示し、かつガス発生抑制に優れたチタン酸リチウム粒子粉末、並びに該材料を負極活物質として使用した非水電解質二次電池を提供する。 The present invention relates to a lithium titanate particle powder that exhibits excellent initial discharge capacity and excellent gas generation suppression as a negative electrode active material for a non-aqueous electrolyte secondary battery, and a non-aqueous electrolyte using the material as a negative electrode active material A secondary battery is provided.
　近年、ＡＶ機器やパソコン等の電子機器のポータブル化、コードレス化が急速に進んでおり、これらの駆動用電源として小型、軽量で高エネルギー密度を有する二次電池への要求が高くなっている。このような状況下において、充放電電圧が高く、充放電容量も大きいという長所を有するリチウムイオン二次電池が注目されている。 In recent years, electronic devices such as AV devices and personal computers are rapidly becoming portable and cordless, and there is an increasing demand for secondary batteries having a small size, light weight, and high energy density as power sources for driving these devices. Under such circumstances, a lithium ion secondary battery having advantages such as a high charge / discharge voltage and a large charge / discharge capacity has attracted attention.
　このリチウムイオン二次電池において、近年、負極活物質にチタン酸リチウムを使用することが知られている。 In this lithium ion secondary battery, in recent years, it is known to use lithium titanate as a negative electrode active material.
　チタン酸リチウム：Ｌｉ４Ｔｉ５Ｏ１２は、充放電によるリチウムイオン挿入・脱離反応における結晶構造変化が非常に小さいため、構造安定性が高く、信頼性の高い負極活物質として知られている。 Lithium titanate: Li 4 Ti 5 O 12 is known as a highly reliable negative electrode active material with high structural stability because the crystal structure change in the lithium ion insertion / extraction reaction due to charge / discharge is very small. .
　従来から、チタン酸リチウム（Ｌｉ４Ｔｉ５Ｏ１２）を得るための製造法としては、リチウム塩とチタン酸化物をＬｉ／Ｔｉ比がほぼ０．８０となるように乾式または湿式混合した混合粉末（これらは、単なるリチウム塩とチタン酸化物の混合物である）を加熱焼成してＬｉ４Ｔｉ５Ｏ１２を得る、いわゆる固相反応法（以下、乾式法と言う）が知られている（特許文献１、２）。 Conventionally, as a manufacturing method for obtaining lithium titanate (Li 4 Ti 5 O 12 ), a mixed powder in which a lithium salt and a titanium oxide are dry or wet mixed so that a Li / Ti ratio is approximately 0.80. A so-called solid phase reaction method (hereinafter referred to as a dry method) is known in which Li 4 Ti 5 O 12 is obtained by heating and baking (these are simply a mixture of a lithium salt and a titanium oxide) (patented) References 1, 2).
　一方、チタンとリチウムの混合物を水熱処理して、その後加熱焼成してＬｉ４Ｔｉ５Ｏ１２を得る、液相反応＋固相反応法（以下、湿式法と言う）が知られている（特許文献３、４）。 On the other hand, a liquid phase reaction + solid phase reaction method (hereinafter referred to as a wet method) is known, in which a mixture of titanium and lithium is hydrothermally treated and then heated and fired to obtain Li 4 Ti 5 O 12 (Patent Patent) References 3, 4).
特開２００１－１９２２０８号公報JP 2001-192208 A 特開２００１－２１３６２２号公報JP 2001-213622 A 特開平９－３０９７２７号公報JP-A-9-309727 特開２０１０－２２８９８０号公報JP 2010-228980 A
　これまでの報告では、最終組成物であるＬｉ４Ｔｉ５Ｏ１２の純度をより高めることを目標としており、この純度を高めるほど、電池特性が向上することが知られている。 Previous reports have aimed to further increase the purity of the final composition Li 4 Ti 5 O 12 , and it is known that the higher the purity, the better the battery characteristics.
　しかしながら、不純物相を低減して純度の高いＬｉ４Ｔｉ５Ｏ１２からなるチタン酸リチウム粒子粉末としても、初期放電容量が高く、出力特性に優れ、且つガス発生が抑制できる負極活物質は未だ得られていない。特に、ラミネートタイプのセルでは、ガス発生により、接触不良が起こり、電池特性が劣化するため、極めてガス発生が少ないチタン酸リチウムが望まれている。 However, even when the lithium titanate particle powder made of Li 4 Ti 5 O 12 with high purity by reducing the impurity phase is used, a negative electrode active material having a high initial discharge capacity, excellent output characteristics, and capable of suppressing gas generation has not yet been obtained. It is not done. In particular, in a laminate type cell, contact failure occurs due to gas generation, and battery characteristics deteriorate. Therefore, lithium titanate that generates extremely little gas is desired.
　本発明者らは、目的物であるＬｉ４Ｔｉ５Ｏ１２に含まれるＴｉＯ２とＬｉ２ＴｉＯ３の存在量に着目し、鋭意、検討を行った結果、従来の知見、即ち、Ｌｉ４Ｔｉ５Ｏ１２の純度をより高めるよりも、Ｌｉ２ＴｉＯ３を特定の範囲で存在させ、且つＢＥＴ法による比表面積を特定の範囲に調整することで、初期放電容量、及びガス発生抑制がともに優れた該負極活物質が得られることを見出した。更に、結晶歪みを特定の範囲以下にすることによって、出力特性にも優れた負極活物質を得ることを見出し、本発明に至った。 The inventors of the present invention focused on the abundance of TiO 2 and Li 2 TiO 3 contained in the target product Li 4 Ti 5 O 12, and as a result of earnest and examination, as a result of the conventional knowledge, that is, Li 4 Ti Rather than increasing the purity of 5 O 12 , both Li 2 TiO 3 is present in a specific range, and the specific surface area by the BET method is adjusted to a specific range, so both initial discharge capacity and gas generation suppression are excellent. It was also found that the negative electrode active material can be obtained. Furthermore, the inventors have found that a negative electrode active material excellent in output characteristics can be obtained by making the crystal distortion below a specific range, and the present invention has been achieved.
　前記技術的課題は、次の通りの本発明によって達成できる。 The technical problem can be achieved by the present invention as follows.
　すなわち、本発明は、スピネル構造を有するチタン酸リチウム粒子粉末において、ＸＲＤにてＦｄ－３ｍで指数付けしたとき、リートベルト解析によるＴｉＯ２量が１．５％以下で、Ｌｉ２ＴｉＯ３量が１％以上６％以下の範囲で、Ｌｉ４Ｔｉ５Ｏ１２量が９４％以上９９％以下で、結晶歪みが０．００１５以下で、且つ、ＢＥＴ法による比表面積が２ｍ２／ｇ以上７ｍ２／ｇ以下の範囲であることを特徴とするチタン酸リチウム粒子粉末である（本発明１）。 That is, according to the present invention, when lithium titanate particles having a spinel structure are indexed with Fd-3m by XRD, the amount of TiO 2 by Rietveld analysis is 1.5% or less, and the amount of Li 2 TiO 3 is In the range of 1% to 6%, the amount of Li 4 Ti 5 O 12 is 94% to 99%, the crystal distortion is 0.0015 or less, and the specific surface area by the BET method is 2 m 2 / g to 7 m 2. Lithium titanate particle powder characterized by being in a range of not more than / g (Invention 1).
　また、本発明は、Ｌｉ／Ｔｉ比（モル比）が０．８０１～０．８３の範囲である本発明１に記載のチタン酸リチウム粒子粉末である（本発明２）。 Further, the present invention is the lithium titanate particle powder according to the present invention 1 having a Li / Ti ratio (molar ratio) in the range of 0.801 to 0.83 (present invention 2).
　また、本発明は、本発明１または本発明２に記載のチタン酸リチウム粒子粉末からなる負極活物質粒子粉末である（本発明３）。 Further, the present invention is a negative electrode active material particle powder comprising the lithium titanate particle powder according to the present invention 1 or the present invention 2 (Invention 3).
　また、本発明は、本発明３記載の負極活物質粒子粉末を使用し、対極をリチウム金属としたセルにおいて、リチウムが挿入される方向を充電としたときに、初期放電容量が１６５ｍＡｈ／ｇ以上で、且つ対極にマンガン酸リチウムを使用したラミネートタイプのセルによるガス発生量が１．０ｃｃ／ｇ以下である本発明３記載の非水電解質二次電池用負極活物質粒子粉末である（本発明４）。 Further, in the present invention, when the negative electrode active material particle powder according to the present invention 3 is used and the counter electrode is lithium metal, the initial discharge capacity is 165 mAh / g or more when the direction in which lithium is inserted is charged. And a negative electrode active material particle powder for a non-aqueous electrolyte secondary battery according to the present invention 3, wherein the amount of gas generated by a laminate type cell using lithium manganate as a counter electrode is 1.0 cc / g or less (the present invention). 4).
　また、本発明は、本発明３又は４に記載の負極活物質粒子粉末を使用した非水電解質二次電池である（本発明５）。 Further, the present invention is a non-aqueous electrolyte secondary battery using the negative electrode active material particle powder according to the present invention 3 or 4 (invention 5).
　本発明に係るチタン酸リチウム粒子粉末は、負極活物質粒子粉末として非水電解質二次電池に用いた場合に、優れた初期放電容量及び出力特性を示し、且つ、ガス発生が抑制されたバランスの良い電池特性が得られるので非水電解質二次電池用の活物質粒子粉末として好適である。 The lithium titanate particle powder according to the present invention exhibits excellent initial discharge capacity and output characteristics when used in a non-aqueous electrolyte secondary battery as a negative electrode active material particle powder, and has a balance in which gas generation is suppressed. Since good battery characteristics are obtained, it is suitable as an active material particle powder for a non-aqueous electrolyte secondary battery.
実施例１で得られたチタン酸リチウム粒子粉末のＸＲＤパターンである。2 is an XRD pattern of lithium titanate particle powder obtained in Example 1. FIG. 実施例２で得られたチタン酸リチウム粒子粉末の走査型電子顕微鏡写真である。2 is a scanning electron micrograph of lithium titanate particle powder obtained in Example 2. FIG.
　本発明の構成をより詳しく説明すれば次の通りである。 The configuration of the present invention will be described in more detail as follows.
　本発明に係るチタン酸リチウム粒子粉末は、少なくともスピネル構造であり、一般化学式でＬｉ４Ｔｉ５Ｏ１２と記載できる化合物であり、且つ、少なくともＬｉ２ＴｉＯ３を含有している。 The lithium titanate particle powder according to the present invention has at least a spinel structure, is a compound that can be expressed as Li 4 Ti 5 O 12 in a general chemical formula, and contains at least Li 2 TiO 3 .
　本発明に係るチタン酸リチウム粒子粉末におけるＬｉ２ＴｉＯ３の存在状態は、本発明で特定する範囲の量であれば、粒子表面に被覆された状態やアイランド状に存在していてもよく、また、粒内ではどのような形状で存在していてもよい。 The presence state of Li 2 TiO 3 in the lithium titanate particle powder according to the present invention may be in a state of being coated on the particle surface or in an island shape as long as it is in an amount specified by the present invention, Any shape may be present in the grains.
　本発明に係るチタン酸リチウム粒子粉末は、ＸＲＤで１０～９０度（２θ／θ）間の回折がＦｄ－３ｍで指数付けできる。ＸＲＤパターンからリートベルト解析を行うことで、残留したＴｉＯ２量とＬｉ２ＴｉＯ３量を定量することができる。 In the lithium titanate particle powder according to the present invention, diffraction between 10 to 90 degrees (2θ / θ) can be indexed with Fd-3m in XRD. By performing Rietveld analysis from the XRD pattern, the amount of residual TiO 2 and the amount of Li 2 TiO 3 can be quantified.
　本発明において、ＴｉＯ２の存在量は１．５％以下であり、Ｌｉ２ＴｉＯ３の存在量は１．０～６．０％の範囲である。ＴｉＯ２の存在量が１．５％を超えると、出力特性が悪くなる。Ｌｉ２ＴｉＯ３の存在量が１．０％未満の場合、このチタン酸リチウム粒子粉末を負極活物質粒子粉末として用いて作製した二次電池の初期放電容量、出力特性は良好であるが、ガス発生が多くなる。また、Ｌｉ２ＴｉＯ３の存在量が６．０％を超えると、このチタン酸リチウム粒子粉末を負極活物質粒子粉末として用いて作製した二次電池の初期放電容量が低くなり、１６５ｍＡｈ／ｇ以上の高容量を満たすことができなくなる。好ましくはＴｉＯ２の存在量は１．０％以下であり、Ｌｉ２ＴｉＯ３の存在量は１．５～５．０％であって、より好ましくはＴｉＯ２の存在量は０．５％以下であり、Ｌｉ２ＴｉＯ３の存在量は２．０～４．０％である。 In the present invention, the abundance of TiO 2 is 1.5% or less, and the abundance of Li 2 TiO 3 is in the range of 1.0 to 6.0%. When the amount of TiO 2 exceeds 1.5%, the output characteristics are deteriorated. When the abundance of Li 2 TiO 3 is less than 1.0%, the initial discharge capacity and output characteristics of the secondary battery produced using this lithium titanate particle powder as the negative electrode active material particle powder are good, but the gas Occurrence increases. Further, if the amount of Li 2 TiO 3 exceeds 6.0%, the initial discharge capacity of a secondary battery produced using this lithium titanate particle powder as the negative electrode active material particle powder becomes low, 165 mAh / g or more. The high capacity of can not be satisfied. Preferably, the abundance of TiO 2 is 1.0% or less, the abundance of Li 2 TiO 3 is 1.5 to 5.0%, more preferably the abundance of TiO 2 is 0.5% or less. And the abundance of Li 2 TiO 3 is 2.0 to 4.0%.
　本発明に係るチタン酸リチウム粒子粉末のＢＥＴ法による比表面積は２ｍ２／ｇ以上７ｍ２／ｇ以下の範囲である。比表面積がこの範囲より小さいと、電池容量が小さくなってしまい実用性に欠ける。この範囲より大きいとガスが発生しやすくなり電池の膨れが顕著になる。好ましい比表面積は２．２～６．８ｍ２／ｇであり、さらにより好ましくは２．４～６．６ｍ２／ｇである。 BET specific surface area of the lithium titanate particles according to the present invention is in the range of less 2m 2 / g or more 7m 2 / g. If the specific surface area is smaller than this range, the battery capacity becomes small and the practicality is lacking. If it is larger than this range, gas is likely to be generated and the battery swells significantly. Preferred specific surface area of 2.2 ~ 6.8m 2 / g, even more preferably 2.4 ~ 6.6m 2 / g.
　本発明ではチタン酸リチウム粒子粉末をＸＲＤ測定し、リートベルト解析によりチタン酸リチウム粒子粉末の結晶歪みを求めることができる。ＸＲＤ測定条件は２θ／θで１０～９０度の範囲を０．０２度ステップスキャンした。 In the present invention, the lithium titanate particle powder is subjected to XRD measurement, and the crystal distortion of the lithium titanate particle powder can be obtained by Rietveld analysis. The XRD measurement condition was 2θ / θ, and a range of 10 to 90 degrees was scanned 0.02 degrees.
　得られたＸＲＤ回折からリートベルト解析を行った結果、本発明にある結晶歪みの範囲が好適であることが分かった。本発明において、結晶歪みが０．００１５を超えると出力特性が悪くなる。結晶歪みの好ましい範囲は０．００１４以下であり、更に好ましい範囲は０．０００１～０．００１３である。 As a result of Rietveld analysis from the obtained XRD diffraction, it was found that the range of crystal distortion in the present invention is suitable. In the present invention, when the crystal strain exceeds 0.0015, the output characteristics deteriorate. A preferable range of crystal distortion is 0.0014 or less, and a more preferable range is 0.0001 to 0.0013.
　本発明では、チタン酸リチウム粒子粉末のＬｉ２ＴｉＯ３存在量、比表面積及び結晶歪みなどの各種特性が本発明で規定する条件を満たすことで、下記のような効果をもたらされていると考えられる。 In the present invention, the following effects are brought about by satisfying the conditions defined in the present invention by various characteristics such as Li 2 TiO 3 abundance, specific surface area and crystal distortion of the lithium titanate particle powder. Conceivable.
　一般的に活物質は比表面積が小さいことでガス発生を抑制することができると考えられる。しかしながら、後述比較例６に示すように、比表面積を小さくしすぎると、初期容量も小さくなってしまう。本発明者らは、ガス発生について、比表面積以外の制御パラメータを検討した結果、チタン酸リチウム粉末中のＬｉ２ＴｉＯ３量にも関係していることを見出した。この作用は定かではないが、Ｌｉ２ＴｉＯ３がチタン酸リチウム粒子内若しくは表層に存在することで、チタン酸リチウムが満充電によりＬｉ７Ｔｉ５Ｏ１２となったときに、粒子全体ではなくＬｉ２ＴｉＯ３の存在ポイントが残り、その結果ガス発生が小さくなると考えている。 In general, it is considered that an active material can suppress gas generation due to its small specific surface area. However, as shown in Comparative Example 6 described later, if the specific surface area is too small, the initial capacity is also reduced. As a result of examining control parameters other than the specific surface area for gas generation, the present inventors have found that it is also related to the amount of Li 2 TiO 3 in the lithium titanate powder. Although this effect is not clear, when Li 2 TiO 3 is present in the lithium titanate particles or in the surface layer, when lithium titanate becomes Li 7 Ti 5 O 12 by full charge, not Li The existence point of 2 TiO 3 remains, and as a result, gas generation is considered to be small.
　一方、出力特性を大きくする手法として、比表面積を大きくする処方（例えば、微粒子化する方法）が行われるが、微粒子化に伴う際に粒子にダメージ（応力の残留や化学組成の変化）が発生するために粒子に歪みが残ってしまう。この歪みが本発明の範囲より大きいと急激に出力特性が悪化してしまうことが分かった。 On the other hand, as a method to increase the output characteristics, a prescription for increasing the specific surface area (for example, a method for making fine particles) is performed, but damage to the particles (residual stress or change in chemical composition) occurs when making fine particles. As a result, distortion remains in the particles. It has been found that when this distortion is larger than the range of the present invention, the output characteristics deteriorate rapidly.
　従って、チタン酸リチウム粒子粉末のＬｉ２ＴｉＯ３存在量と比表面積及び結晶歪みを特定の範囲に制御することで、非水電解質二次電池用の活物質粒子粉末として用いた場合、バランスのとれた電池特性を得ることが可能となる。 Therefore, by using the Li 2 TiO 3 abundance, specific surface area, and crystal distortion of the lithium titanate particle powder within a specific range, a balance can be obtained when used as an active material particle powder for a non-aqueous electrolyte secondary battery. Battery characteristics can be obtained.
　本発明に係るチタン酸リチウム粒子粉末のＬｉ／Ｔｉ比（モル比）は０．８０１～０．８３が好ましい。チタン酸リチウム粒子粉末のＬｉ／Ｔｉ比（モル比）が前記範囲外の場合、Ｌｉ２ＴｉＯ３などの不純物相が多量に生成し、その結果、非水電解質二次電池としたときに初期充電容量が小さくなるので、好ましくない。より好ましいＬｉ／Ｔｉ比（モル比）は０．８０３～０．８２８、更に好ましくは０．８０５～０．８２７、更により好ましくは０．８０７～０．８２６である。 The Li / Ti ratio (molar ratio) of the lithium titanate particles according to the present invention is preferably 0.801 to 0.83. When the Li / Ti ratio (molar ratio) of the lithium titanate particle powder is out of the above range, a large amount of impurity phase such as Li 2 TiO 3 is generated, and as a result, the initial charge is obtained when a non-aqueous electrolyte secondary battery is obtained. Since the capacity is small, it is not preferable. A more preferable Li / Ti ratio (molar ratio) is 0.803 to 0.828, more preferably 0.805 to 0.827, and still more preferably 0.807 to 0.826.
　次に、本発明に係るチタン酸リチウム粒子粉末の製造方法について述べる。 Next, a method for producing lithium titanate particle powder according to the present invention will be described.
　本発明に係るチタン酸リチウム粒子粉末の製造方法は、特に制限されるものではなく、湿式法／乾式法といった方法にて合成することができる。 The production method of the lithium titanate particle powder according to the present invention is not particularly limited, and can be synthesized by a method such as a wet method / dry method.
　以下にチタン酸リチウム粒子粉末を乾式法で製造した場合の一例を示す。 An example in the case where lithium titanate particle powder is produced by a dry method is shown below.
　例えば、少なくともリチウム化合物とＴｉＯ２とを所定の本発明にあるＬｉ／Ｔｉとなるように秤量して、均一混合することで混合物を得、当該混合物を７００～９００℃で焼成し、粉砕することによりチタン酸リチウム粒子粉末が得られる。 For example, at least a lithium compound and TiO 2 are weighed so as to be a predetermined Li / Ti in the present invention, and uniformly mixed to obtain a mixture, and the mixture is fired at 700 to 900 ° C. and pulverized. Thus, lithium titanate particle powder is obtained.
　本発明に用いることができるリチウム化合物は炭酸リチウム、水酸化リチウム、酢酸リチウム、硝酸リチウム、酸化リチウムといったものがあるが、安価な炭酸リチウムが好ましい。 The lithium compounds that can be used in the present invention include lithium carbonate, lithium hydroxide, lithium acetate, lithium nitrate, and lithium oxide, but inexpensive lithium carbonate is preferable.
　本発明に用いるＴｉＯ２は、特に制限はなく、含水和物も用いることが出来る。使用するＴｉＯ２は、結晶子サイズが１０～１００ｎｍであることが好ましい。また、ＴｉＯ２含水和物の場合は、１～２０ｎｍであることが好ましい。該結晶子サイズより大きい場合は、合成において異相が大きく生成してしまい、本発明の目的とするチタン酸リチウム粒子粉末を得ることが困難となる。また、本発明において用いることができるＴｉＯ２は、アナターゼ型とルチル型と、その混相があるが、アナターゼ型が好ましい。 TiO 2 used in the present invention is not particularly limited, water hydrates can also be used. The TiO 2 to be used preferably has a crystallite size of 10 to 100 nm. In the case of TiO 2 hydrate, the thickness is preferably 1 to 20 nm. If it is larger than the crystallite size, a large amount of heterogeneous phase is generated in the synthesis, making it difficult to obtain the target lithium titanate particle powder of the present invention. In addition, TiO 2 that can be used in the present invention has an anatase type, a rutile type, and a mixed phase thereof, and an anatase type is preferable.
　本発明に係るチタン酸リチウム粒子粉末の製造に用いるリチウム化合物とＴｉＯ２は、焼成後のＬｉ／Ｔｉ比で０．８０１～０．８３となるように調整し混合することが好ましい。前記範囲に調整するためには、リチウム化合物とＴｉＯ２との混合比を調整することによって行うことができる。Ｌｉ／Ｔｉを理論比の０．８０より大きくする理由は、より結晶性の高いチタン酸リチウムを得ると共に、焼成後にＬｉ２ＴｉＯ３を残留させることにある。上記範囲より大きすぎると、初期放電容量が低下し、尚且つＬｉ２ＴｉＯ３残留物が更に多くなることにより得られたチタン酸リチウム粒子粉末は残留アルカリが多くなり、塗料のゲル化が起こる。 The lithium compound and TiO 2 used for producing the lithium titanate particle powder according to the present invention are preferably adjusted and mixed so that the Li / Ti ratio after firing is 0.801 to 0.83. To adjust the range, it can be done by adjusting the mixing ratio of the lithium compound and TiO 2. The reason why Li / Ti is made larger than the theoretical ratio of 0.80 is to obtain lithium titanate having higher crystallinity and to leave Li 2 TiO 3 after firing. If it is larger than the above range, the initial discharge capacity is decreased, and the lithium titanate particles obtained by further increasing the Li 2 TiO 3 residue have a large residual alkali, resulting in gelation of the paint.
　該混合物は７００～９００℃で焼成することにより本発明にあるチタン酸リチウム粒子粉末が得られる。焼成温度が７００℃未満であるとＴｉＯ２が多量に残留してしまう。焼成温度が高すぎると、リチウムの蒸発量が多くなりＴｉＯ２相が多量に発生してしまう。焼成温度は好ましくは７００～８８０℃である。ただし、用いるＴｉＯ２の特性（ＢＥＴ比表面積、結晶子径等）に応じて反応の進行程度が異なるので、好ましい焼成温度の温度範囲は変動する。 The mixture is fired at 700 to 900 ° C. to obtain the lithium titanate particle powder according to the present invention. If the firing temperature is less than 700 ° C., a large amount of TiO 2 remains. If the firing temperature is too high, the amount of lithium evaporation increases and a large amount of TiO 2 phase is generated. The firing temperature is preferably 700 to 880 ° C. However, since the progress of the reaction varies depending on the characteristics of the TiO 2 used (BET specific surface area, crystallite diameter, etc.), the preferred temperature range of the firing temperature varies.
　焼成における雰囲気は、酸化性雰囲気であっても還元雰囲気であってもよい。本発明において得られたチタン酸リチウム粒子粉末は、公知な技術の範囲において酸素欠損若しくは酸素過剰があってもよい。 The atmosphere in firing may be an oxidizing atmosphere or a reducing atmosphere. The lithium titanate particle powder obtained in the present invention may have oxygen deficiency or oxygen excess within the range of known techniques.
　焼成して得られたチタン酸リチウム粒子粉末は、粉砕することで粒度分布を整えることもできる。その粒度分布の形状は、シャープでもブロードでも、バイモーダルでもよい。粉砕には、ボールミル、ビーズミル、ハンマーミルなどが使用できる。 The particle size distribution can be adjusted by pulverizing the lithium titanate particle powder obtained by firing. The shape of the particle size distribution may be sharp, broad, or bimodal. A ball mill, a bead mill, a hammer mill or the like can be used for pulverization.
　本発明においては、原料混合粉のＬｉ／Ｔｉ比、焼成温度及び焼成時間、粉砕条件をそれぞれ組みわせることによって目的とするチタン酸リチウム粒子粉末を得ることができる。例えば、比較的高温で熱処理した場合には比表面積が低いものが得られる傾向にあり、また、粉砕時間が長くなれば、結晶歪が大きくなる傾向にある。 In the present invention, the target lithium titanate particle powder can be obtained by combining the Li / Ti ratio, firing temperature and firing time, and pulverization conditions of the raw material mixed powder. For example, when heat treatment is performed at a relatively high temperature, a product having a low specific surface area tends to be obtained, and when the pulverization time is increased, crystal strain tends to increase.
　本発明に係るチタン酸リチウム粒子粉末は、非水電解質二次電池用負極活物質粒子粉末として用いることができる。 The lithium titanate particle powder according to the present invention can be used as a negative electrode active material particle powder for a non-aqueous electrolyte secondary battery.
　次に、本発明に係る負極活物質粒子粉末を含有する負極、並びに非水電解質二次電池について述べる。 Next, the negative electrode containing the negative electrode active material particle powder and the nonaqueous electrolyte secondary battery according to the present invention will be described.
　本発明に係る負極活物質粒子粉末を含有する負極を製造する場合には、常法に従って、導電剤と結着剤とを添加混合する。導電剤としてはアセチレンブラック、カーボンブラック、黒鉛等が好ましく、結着剤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等が好ましい。 In the case of producing a negative electrode containing the negative electrode active material particle powder according to the present invention, a conductive agent and a binder are added and mixed according to a conventional method. As the conductive agent, acetylene black, carbon black, graphite and the like are preferable, and as the binder, polytetrafluoroethylene, polyvinylidene fluoride and the like are preferable.
　本発明に係る負極用活物質粒子粉末を含有する負極を用いて製造される二次電池は、正極、負極及び電解質から構成される。 The secondary battery manufactured using the negative electrode containing the negative electrode active material particle powder according to the present invention includes a positive electrode, a negative electrode, and an electrolyte.
　正極活物質としては、一般的な非水電解質二次電池用の正極材であるコバルト酸リチウム、マンガン酸リチウム、ニッケル酸リチウム等を用いることができる。 As the positive electrode active material, lithium cobaltate, lithium manganate, lithium nickelate or the like, which is a positive electrode material for a general non-aqueous electrolyte secondary battery, can be used.
　また、電解液の溶媒としては、炭酸エチレンと炭酸ジエチルの組み合わせ以外に、炭酸プロピレン、炭酸ジメチル等のカーボネート類や、ジメトキシエタン等のエーテル類の少なくとも１種類を含む有機溶媒を用いることができる。 In addition to the combination of ethylene carbonate and diethyl carbonate, an organic solvent containing at least one of carbonates such as propylene carbonate and dimethyl carbonate and ethers such as dimethoxyethane can be used as the solvent for the electrolytic solution.
　さらに、電解質としては、六フッ化リン酸リチウム以外に、過塩素酸リチウム、四フッ化ホウ酸リチウム等のリチウム塩の少なくとも１種類を上記溶媒に溶解して用いることができる。 Further, as the electrolyte, in addition to lithium hexafluorophosphate, at least one lithium salt such as lithium perchlorate and lithium tetrafluoroborate can be dissolved in the above solvent and used.
　本発明に係る負極用活物質粒子粉末を含有する電極を用いて製造した非水電解質二次電池は、後述する評価法で１．０Ｖ以上の初期放電容量が１６５ｍＡｈ／ｇ以上である。 The non-aqueous electrolyte secondary battery manufactured using the electrode containing the negative electrode active material particle powder according to the present invention has an initial discharge capacity of 1.0 V or higher by an evaluation method described later of 165 mAh / g or higher.
　また、本発明に係る負極用活物質粒子粉末を負極とし、正極にマンガン酸リチウムを用いて製造した非水電解質二次電池にて、後述する評価法でガス発生量は１．０ｃｃ／ｃｍ３未満である。 Moreover, in the nonaqueous electrolyte secondary battery manufactured using the negative electrode active material particle powder according to the present invention as the negative electrode and using lithium manganate as the positive electrode, the gas generation amount was 1.0 cc / cm 3 according to the evaluation method described later. Is less than.
　なお、本発明に係るチタン酸リチウム粒子粉末は、正極活物質として用いることも可能である。 The lithium titanate particle powder according to the present invention can also be used as a positive electrode active material.
　本発明に係るチタン酸リチウム粒子粉末を正極活物質として用いる場合、非水電解質二次電池は、前記の電極、対極および電解質からなり、対極（負極）には金属リチウム、リチウム合金等、あるいはグラファイト、コークスなどの炭素系材料が用いられる。 When the lithium titanate particle powder according to the present invention is used as a positive electrode active material, the non-aqueous electrolyte secondary battery is composed of the above electrode, counter electrode and electrolyte, and the counter electrode (negative electrode) is metallic lithium, lithium alloy, or graphite. Carbonaceous materials such as coke are used.
　　＜作用＞
　本発明において最も重要な点は、本発明に係る特定量のＬｉ２ＴｉＯ３が存在し、且つ本発明範囲にある比表面積や結晶歪みを有するチタン酸リチウム粒子粉末を用いることで、二次電池として優れた初期放電容量や出力特性を有し、且つガス発生を抑制できる非水電解質二次電池を得ることができるという点である。 <Action>
The most important point in the present invention is the use of a lithium titanate particle powder having a specific surface area and crystal distortion within the range of the present invention, in which a specific amount of Li 2 TiO 3 according to the present invention is present. It is possible to obtain a non-aqueous electrolyte secondary battery that has excellent initial discharge capacity and output characteristics and can suppress gas generation.
　従来は、Ｘ線回折によるピーク強度比を基準として、不純物相を低減して純度の高いＬｉ４Ｔｉ５Ｏ１２からなるチタン酸リチウム粒子粉末を得ることが行われてきた。しかしながら、単に、高純度にすることだけでは、初期放電容量が高く、且つガス発生が抑制できるという特性を十分に満たせるものではなかった。 Conventionally, on the basis of the peak intensity ratio by X-ray diffraction, the impurity phase has been reduced to obtain lithium titanate particle powder made of Li 4 Ti 5 O 12 having high purity. However, simply making it high purity does not sufficiently satisfy the characteristics that the initial discharge capacity is high and gas generation can be suppressed.
　本発明者らは、Ｘ線回折のピーク強度比による定量よりも、より正確に定量できるリートベルト解析によって不純物相を定量するとともに、ごく微量のＬｉ２ＴｉＯ３が存在させ、しかも、ＢＥＴ比表面積と結晶歪みを制御することによって、高い電池特性を示す負極活物質を得ることが可能となった。 The present inventors have quantified the impurity phase by Rietveld analysis, which can be more accurately quantified than the quantification by the peak intensity ratio of X-ray diffraction, the presence of a very small amount of Li 2 TiO 3 , and the BET specific surface area. By controlling the crystal strain, it is possible to obtain a negative electrode active material exhibiting high battery characteristics.
　本発明の代表的な実施の形態は、次の通りである。 A typical embodiment of the present invention is as follows.
　ＢＥＴ比表面積は試料を窒素ガス下で１２０℃、４５分間乾燥脱気した後、マックソーブＨＭ　Ｍｏｄｅｌ－１２０８　マウンテック（株）製を用いて測定した。 The BET specific surface area was measured by using a Macsorb HM Model-1208 manufactured by Mountech Co., Ltd. after drying and deaeration of the sample under nitrogen gas at 120 ° C. for 45 minutes.
　Ｌｉ／Ｔｉ比は、調整液を作製し、ＩＣＰ測定には、ｉＣＡＰ６５００　サーモフィッシャーサイエンティフィック（株）製を用いて各元素を定量して決定した。 The Li / Ti ratio was determined by preparing an adjustment liquid and quantifying each element using ICAP6500 Thermo Fisher Scientific Co., Ltd. for ICP measurement.
　試料のＸ線回折は、株式会社リガク製　ＳｍａｒｔＬａｂを用いて測定した（１０～９０度、０．０２度ステップスキャン）。また、ＴｉＯ２量とＬｉ２ＴｉＯ３量の定量や結晶歪みと結晶子サイズの計算には、Ｘ線回折のデータを用いてリートベルト解析を行うことで算出した。リートベルト解析には、ＲＩＥＴＡＮ２０００を使用した。 The X-ray diffraction of the sample was measured using a SmartLab manufactured by Rigaku Corporation (10 to 90 degrees, 0.02 degree step scan). The amount of TiO 2 and the amount of Li 2 TiO 3 and the calculation of crystal distortion and crystallite size were calculated by performing Rietveld analysis using X-ray diffraction data. Rietan2000 was used for Rietveld analysis.
　本発明に係る負極活物質粒子粉末については、２０３２型コインセルを用いて電池評価を行った。 The negative electrode active material particle powder according to the present invention was subjected to battery evaluation using a 2032 type coin cell.
　電池評価に係るコインセルについては、本発明による負極用活物質粒子粉末であるチタン酸リチウムを正極として用い、活物質量を９０重量％、導電材としてアセチレンブラックを２．５重量％、グラファイトを２．５重量％、バインダーとしてＮ－メチルピロリドンに溶解したポリフッ化ビニリデン５重量％とを混合した後、Ａｌ金属箔に塗布し１２０℃にて乾燥した。このシートを１６ｍｍΦに打ち抜いた後、３．０ｔ／ｃｍ２で圧着した物を正極に用いた。対極は１６ｍｍΦに打ち抜いた厚さが５００μｍの金属リチウムとし、電解液は１ｍｏｌ／ＬのＬｉＰＦ６を溶解したＥＣとＤＭＣを体積比で１：２で混合した溶液を用いて２０３２型コインセルを作製した。 For coin cells related to battery evaluation, lithium titanate, which is an active material particle powder for a negative electrode according to the present invention, is used as a positive electrode, the amount of active material is 90% by weight, acetylene black is 2.5% by weight as a conductive material, and graphite is 2%. Then, 5% by weight and 5% by weight of polyvinylidene fluoride dissolved in N-methylpyrrolidone as a binder were mixed, applied to an Al metal foil, and dried at 120 ° C. The sheet was punched out to 16 mmΦ, and then pressure-bonded at 3.0 t / cm 2 was used for the positive electrode. The counter electrode was made of metallic lithium with a thickness of 500 μm punched to 16 mmΦ, and the electrolyte was a 2032 type coin cell using a solution in which EC and DMC in which 1 mol / L LiPF 6 was dissolved was mixed at a volume ratio of 1: 2. .
　充放電特性は、恒温槽で２５℃とした環境下で、充電をＬｉが脱離される方向としたときに、充電は１．０Ｖまで０．１Ｃの電流密度にて行った（ＣＣ－ＣＣ操作）後、放電を３．０Ｖまで０．１Ｃの電流密度にて行った（ＣＣ－ＣＣ操作）。本操作の１回目の充電容量（１ｓｔ－ＣＨ）、放電容量（１ｓｔ－ＤＣＨ）を測定した。測定結果を表２に示す。表２において、初期充電容量が１６５ｍＡｈ／ｇ以上を「〇」、１６５ｍＡｈ／ｇ未満を「×」とした。 Charging / discharging characteristics were as follows: charging was performed at a current density of 0.1 C up to 1.0 V when charging was performed in a direction where Li was desorbed in an environment of a constant temperature bath at 25 ° C. (CC-CC operation) Thereafter, discharging was performed at a current density of 0.1 C up to 3.0 V (CC-CC operation). The first charge capacity (1st-CH) and discharge capacity (1st-DCH) of this operation were measured. The measurement results are shown in Table 2. In Table 2, when the initial charge capacity was 165 mAh / g or more, “◯”, and less than 165 mAh / g, “×”.
　出力特性は、恒温槽で２５℃とした環境下で放電は１．０Ｖまで０．１Ｃの電流密度にて行った（ＣＣ－ＣＣ操作）後、充電は３．０Ｖまで０．１Ｃの電流密度にて行った（ＣＣ－ＣＣ操作）。このときの放電容量をａとする。次に、放電は１．０Ｖまで４Ｃの電流密度にて行った（ＣＣ－ＣＣ操作）後、充電は３．０Ｖまで０．１Ｃの電流密度にて行った（ＣＣ－ＣＣ操作）。このときの放電容量をｂとするとき、出力特性は（ｂ／ａ×１００（％））とした。測定結果を表２に示す。表２において、出力特性が８０以上を「〇」、８０％未満を「×」とした。 The output characteristics were as follows: discharging was performed at a current density of 0.1 C up to 1.0 V in a constant temperature bath at 25 ° C. (CC-CC operation), and charging was performed at a current density of 0.1 C up to 3.0 V (CC-CC operation). Let the discharge capacity at this time be a. Next, discharging was performed at a current density of 4 C up to 1.0 V (CC-CC operation), and charging was performed at a current density of 0.1 C up to 3.0 V (CC-CC operation). When the discharge capacity at this time is b, the output characteristic is (b / a × 100 (%)). The measurement results are shown in Table 2. In Table 2, when the output characteristic is 80 or more, “◯” is set, and when the output characteristic is less than 80%, “X” is set.
　ガス発生量の評価は、以下のとおりの方法でラミネートセルを作製して評価した。 The gas generation amount was evaluated by producing a laminate cell by the following method.
　本発明による負極用活物質粒子粉末であるチタン酸リチウムを９０重量％、導電材としてアセチレンブラックを２．５重量％、グラファイトを２．５重量％、バインダーとしてＮ－メチルピロリドンに溶解したポリフッ化ビニリデン５重量％とを混合した後、Ａｌ金属箔に塗布し１２０℃にて乾燥した。このシートを４０ｍｍ×１００ｍｍ角に切り取った後、３．０ｔ／ｃｍ２で圧密し、負極に用いた。 90% by weight of lithium titanate as negative electrode active material powder according to the present invention, 2.5% by weight of acetylene black as a conductive material, 2.5% by weight of graphite, and polyfluoride dissolved in N-methylpyrrolidone as a binder After mixing with 5% by weight of vinylidene, it was applied to an Al metal foil and dried at 120 ° C. This sheet was cut into a 40 mm × 100 mm square, and then consolidated at 3.0 t / cm 2 to be used as a negative electrode.
　対極にはＬｉ１．０７Ｍｎ１．８３Ａｌ０．１Ｏ４を９２重量％、導電材としてアセチレンブラックを２．５重量％、グラファイトを２．５重量％、バインダーとしてＮ－メチルピロリドンに溶解したポリフッ化ビニリデン３重量％とを混合した後、Ａｌ金属箔に塗布し１２０℃にて乾燥し、このシートを４０ｍｍ×１００ｍｍ角に切り取った後、３．０ｔ／ｃｍ２で圧密したものを用いた。 At the counter electrode, Li 1.07 Mn 1.83 Al 0.1 O 4 was 92% by weight, acetylene black was 2.5% by weight as a conductive material, graphite was 2.5% by weight, and dissolved in N-methylpyrrolidone as a binder. 3% by weight of polyvinylidene fluoride was mixed, applied to an Al metal foil, dried at 120 ° C., cut into a 40 mm × 100 mm square, and then consolidated at 3.0 t / cm 2 . It was.
　これらの電極を２セット対向するように組み合わせてラミネートセルを作成した。 A laminate cell was prepared by combining two sets of these electrodes so as to face each other.
　上記ラミネートセルにおいて、まず室温で初期の充放電を行った後、２．７Ｖまで充電を行い、この電圧でのラミネートセルの容積を測定した。次に、測定後のセルを６０℃環境下で２４時間保存した後、再度、ラミネートセルの容積を測定し、高温保存前後の容積変化からガス発生量を評価した。測定結果を表２に示す。表２において、ガス発生量が１．０ｃｃ／ｇ以下を「〇」、１．０ｃｃ／ｇを超えるものを「×」とした。 In the above laminate cell, the initial charge / discharge was performed at room temperature, and then charged to 2.7 V, and the volume of the laminate cell at this voltage was measured. Next, after storing the cell after measurement for 24 hours in an environment of 60 ° C., the volume of the laminate cell was measured again, and the amount of gas generated was evaluated from the volume change before and after high-temperature storage. The measurement results are shown in Table 2. In Table 2, the gas generation amount of 1.0 cc / g or less was designated as “◯”, and the gas generation amount exceeding 1.0 cc / g was designated as “x”.
　実施例１：
　比表面積５０ｍ２／ｇのＴｉＯ２と炭酸リチウムをＬｉ／Ｔｉ比のモル比で０．８５に調整し、ライカイキにて１ｈｒ混合した。該混合粉末をアルミナるつぼに入れ、マッフル炉で、温度８５０℃で６時間、空気雰囲気中で焼成を行い、チタン酸リチウム粒子粉末を得た。このチタン酸リチウムをボールミルで１．５時間粉砕してチタン酸リチウム粉末を得た。 Example 1:
TiO 2 having a specific surface area of 50 m 2 / g and lithium carbonate were adjusted to a molar ratio of Li / Ti ratio of 0.85, and mixed for 1 hr with Reiki. The mixed powder was put into an alumina crucible and fired in a muffle furnace at a temperature of 850 ° C. for 6 hours in an air atmosphere to obtain lithium titanate particle powder. This lithium titanate was pulverized with a ball mill for 1.5 hours to obtain a lithium titanate powder.
　比較例１：
　Ｌｉ／Ｔｉ比のモル比を０．８０に変えた以外は、実施例１と同様に処理して、チタン酸リチウム粒子粉末を得た。 Comparative Example 1:
Except having changed the molar ratio of Li / Ti ratio into 0.80, it processed similarly to Example 1 and obtained lithium titanate particle powder.
　実施例２：
　ボールミルでの粉砕時間を３時間に変えた以外は、実施例１と同様に処理して、チタン酸リチウム粒子粉末を得た。 Example 2:
A lithium titanate particle powder was obtained in the same manner as in Example 1 except that the pulverization time in the ball mill was changed to 3 hours.
　比較例２：
　ボールミルでの粉砕時間を６時間に変えた以外は、実施例１と同様に処理して、チタン酸リチウム粒子粉末を得た。 Comparative Example 2:
A lithium titanate particle powder was obtained in the same manner as in Example 1 except that the pulverization time in the ball mill was changed to 6 hours.
　実施例３：
　比表面積３３０ｍ２／ｇのＴｉＯ２と炭酸リチウムをＬｉ／Ｔｉ比のモル比で０．８２に調整し、ライカイキにて１ｈｒ混合した。該混合粉末をアルミナるつぼに入れ、マッフル炉で、温度７５０℃で４時間、空気雰囲気中で焼成を行い、チタン酸リチウム粒子粉末を得た。このチタン酸リチウムをボールミルで０．５時間粉砕してチタン酸リチウム粉末を得た。 Example 3:
TiO 2 having a specific surface area of 330 m 2 / g and lithium carbonate were adjusted to 0.82 at a molar ratio of Li / Ti ratio, and mixed for 1 hr with Reiki. The mixed powder was put into an alumina crucible and fired in a muffle furnace at a temperature of 750 ° C. for 4 hours in an air atmosphere to obtain lithium titanate particle powder. This lithium titanate was pulverized with a ball mill for 0.5 hours to obtain a lithium titanate powder.
　比較例３：
　Ｌｉ／Ｔｉ比のモル比を０．９０に変えた以外は、実施例３と同様に処理して、チタン酸リチウム粒子粉末を得た。 Comparative Example 3:
A lithium titanate particle powder was obtained in the same manner as in Example 3 except that the molar ratio of Li / Ti ratio was changed to 0.90.
　実施例４：
　比表面積８ｍ２／ｇのＴｉＯ２と炭酸リチウムをＬｉ／Ｔｉ比のモル比で１．００に調整し、ライカイキにて１ｈｒ混合した。該混合粉末をアルミナるつぼに入れ、マッフル炉で、温度８８０℃で１０時間、空気雰囲気中で焼成を行い、チタン酸リチウム粒子粉末を得た。このチタン酸リチウムをボールミルで４時間粉砕してチタン酸リチウム粉末を得た。 Example 4:
TiO 2 having a specific surface area of 8 m 2 / g and lithium carbonate were adjusted to a molar ratio of Li / Ti ratio of 1.00, and mixed for 1 hr with Reiki. The mixed powder was put into an alumina crucible and fired in an air atmosphere at a temperature of 880 ° C. for 10 hours in a muffle furnace to obtain lithium titanate particle powder. This lithium titanate was pulverized with a ball mill for 4 hours to obtain a lithium titanate powder.
　比較例４：
　焼成温度を７５０℃に変えた以外は、実施例４と同様に処理して、チタン酸リチウム粒子粉末を得た。 Comparative Example 4:
A lithium titanate particle powder was obtained in the same manner as in Example 4 except that the firing temperature was changed to 750 ° C.
　実施例５：
　比表面積９０ｍ２／ｇのＴｉＯ２と炭酸リチウムをＬｉ／Ｔｉ比のモル比で０．８３に調整し、ライカイキにて１ｈｒ混合した。該混合粉末をアルミナるつぼに入れ、マッフル炉で、温度８４０℃で４時間、空気雰囲気中で焼成を行い、チタン酸リチウム粒子粉末を得た。このチタン酸リチウムをボールミルで１．５時間粉砕してチタン酸リチウム粉末を得た。 Example 5:
TiO 2 having a specific surface area of 90 m 2 / g and lithium carbonate were adjusted to a molar ratio of Li / Ti ratio of 0.83, and mixed for 1 hr with Reiki. The mixed powder was put into an alumina crucible, and baked in an air atmosphere at a temperature of 840 ° C. for 4 hours in a muffle furnace to obtain lithium titanate particle powder. This lithium titanate was pulverized with a ball mill for 1.5 hours to obtain a lithium titanate powder.
　比較例５：
　ボールミルでの粉砕時間を５時間に変えた以外は、実施例５と同様に処理して、チタン酸リチウム粒子粉末を得た。 Comparative Example 5:
A lithium titanate particle powder was obtained in the same manner as in Example 5 except that the pulverization time in the ball mill was changed to 5 hours.
　実施例６：
　比表面積２８５ｍ２／ｇのＴｉＯ２と炭酸リチウムをＬｉ／Ｔｉ比のモル比で０．８３に調整し、ライカイキにて１ｈｒ混合した。該混合粉末をアルミナるつぼに入れ、マッフル炉で、温度８００℃で３時間、空気雰囲気中で焼成を行い、チタン酸リチウム粒子粉末を得た。このチタン酸リチウムをボールミルで１．５時間粉砕してチタン酸リチウム粉末を得た。 Example 6:
TiO 2 having a specific surface area of 285 m 2 / g and lithium carbonate were adjusted to a molar ratio of Li / Ti ratio of 0.83, and mixed for 1 hr by Reiki. The mixed powder was put into an alumina crucible and fired in an air atmosphere at a temperature of 800 ° C. for 3 hours in a muffle furnace to obtain lithium titanate particle powder. This lithium titanate was pulverized with a ball mill for 1.5 hours to obtain a lithium titanate powder.
　比較例６：
　焼成温度を８５０℃、焼成時間を４時間に変えた以外は、実施例６と同様に処理して、チタン酸リチウム粒子粉末を得た。比較例６では原料のＴｉＯ２のＢＥＴ比表面積が２８５ｍ２／ｇと大きいため反応が進行しやすく、８５０℃の焼成によって、ＢＥＴ比表面積が低いものが得られた。 Comparative Example 6:
A lithium titanate particle powder was obtained in the same manner as in Example 6 except that the firing temperature was changed to 850 ° C. and the firing time was changed to 4 hours. In Comparative Example 6, since the raw material TiO2 had a large BET specific surface area of 285 m 2 / g, the reaction was likely to proceed. By baking at 850 ° C., a low BET specific surface area was obtained.
　比較例７：
　Ｌｉ／Ｔｉ比のモル比を０．８２に変えた以外は、実施例５と同様に処理して、チタン酸リチウム粒子粉末を得た。 Comparative Example 7:
Except having changed the molar ratio of Li / Ti ratio into 0.82, it processed like Example 5 and obtained lithium titanate particle powder.
　実施例及び比較例で得られたチタン酸リチウムの特性と条件を表１、表２に示す。 Tables 1 and 2 show characteristics and conditions of lithium titanate obtained in Examples and Comparative Examples.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　実施例に示すとおり、本発明に係るチタン酸リチウム粒子粉末は、初期放電容量が１６５ｍＡｈ／ｇ以上、出力特性が８０％以上と、ともに高く、しかもガス発生が１．０ｃｃ／ｇ以下と抑制されているので、非水電解質二次電池用の活物質として好適である。 As shown in the examples, the lithium titanate particle powder according to the present invention has an initial discharge capacity of 165 mAh / g or more and an output characteristic of 80% or more, and gas generation is suppressed to 1.0 cc / g or less. Therefore, it is suitable as an active material for a non-aqueous electrolyte secondary battery.
　なお、前記実施例においては、本発明に係るチタン酸リチウム粒子粉末を正極活物質として用いた例を示しているが、本発明に係るチタン酸リチウム粒子粉末を負極活物質として用いた場合にも、非水電解質二次電池の活物質として、優れた特性を発揮できるものである。 In addition, in the said Example, although the example which used the lithium titanate particle powder which concerns on this invention as a positive electrode active material is shown, also when the lithium titanate particle powder which concerns on this invention is used as a negative electrode active material, As an active material of a nonaqueous electrolyte secondary battery, it can exhibit excellent characteristics.
　本発明に係るチタン酸リチウム粒子粉末は、負極活物質粒子粉末として非水電解質二次電池に用いた場合に、優れた初期放電容量及び出力特性を示し、且つ、ガス発生が抑制されたバランスの良い電池特性が得られるので非水電解質二次電池用の活物質粒子粉末として好適である。 The lithium titanate particle powder according to the present invention exhibits excellent initial discharge capacity and output characteristics when used in a non-aqueous electrolyte secondary battery as a negative electrode active material particle powder, and has a balance in which gas generation is suppressed. Since good battery characteristics are obtained, it is suitable as an active material particle powder for a non-aqueous electrolyte secondary battery.

Claims (5)

  1. 　スピネル構造を有するチタン酸リチウム粒子粉末において、ＸＲＤにてＦｄ－３ｍで指数付けしたとき、リートベルト解析によるＴｉＯ２量が１．５％以下で、Ｌｉ２ＴｉＯ３量が１％以上６％以下の範囲で、Ｌｉ４Ｔｉ５Ｏ１２量が９４％以上９９％以下で、結晶歪みが０．００１５以下で、且つ、ＢＥＴ法による比表面積が２ｍ２／ｇ以上７ｍ２／ｇ以下の範囲であることを特徴とするチタン酸リチウム粒子粉末。 In a lithium titanate particle powder having a spinel structure, when indexed with Fd-3m by XRD, the amount of TiO 2 by Rietveld analysis is 1.5% or less, and the amount of Li 2 TiO 3 is 1% or more and 6% or less In this range, the amount of Li 4 Ti 5 O 12 is 94% or more and 99% or less, the crystal strain is 0.0015 or less, and the specific surface area by the BET method is 2 m 2 / g or more and 7 m 2 / g or less. Lithium titanate particle powder characterized by being.
  2. 　Ｌｉ／Ｔｉ比（モル比）が０．８０１～０．８３の範囲である請求項１に記載のチタン酸リチウム粒子粉末。 The lithium titanate particle powder according to claim 1, wherein the Li / Ti ratio (molar ratio) is in the range of 0.801 to 0.83.
  3. 　請求項１または請求項２に記載のチタン酸リチウム粒子粉末からなる負極活物質粒子粉末。 Negative electrode active material particle powder comprising the lithium titanate particle powder according to claim 1 or 2.
  4. 　請求項３記載の負極活物質粒子粉末を使用し、対極をリチウム金属としたセルにおいて、リチウムが挿入される方向を充電としたときに、初期放電容量が１６５ｍＡｈ／ｇ以上で、且つ対極にマンガン酸リチウムを使用したラミネートタイプのセルによるガス発生量が１．０ｃｃ／ｇ以下である請求項３記載の非水電解質二次電池用負極活物質粒子粉末。 In a cell using the negative electrode active material powder according to claim 3 and having a counter electrode made of lithium metal, when the charging direction is lithium, the initial discharge capacity is 165 mAh / g or more and manganese is used as the counter electrode. The negative electrode active material particle powder for a non-aqueous electrolyte secondary battery according to claim 3, wherein a gas generation amount by a laminate type cell using lithium acid is 1.0 cc / g or less.
  5. 　請求項３又は４に記載の負極活物質粒子粉末を使用した非水電解質二次電池。 A non-aqueous electrolyte secondary battery using the negative electrode active material particle powder according to claim 3 or 4.
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