WO2012147864A1 - チタン酸リチウム前駆体の製造方法、チタン酸リチウムの製造方法、チタン酸リチウム、電極活物質および蓄電デバイス - Google Patents
チタン酸リチウム前駆体の製造方法、チタン酸リチウムの製造方法、チタン酸リチウム、電極活物質および蓄電デバイス Download PDFInfo
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- lithium titanate
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D15/00—Lithium compounds
- C01D15/02—Oxides; Hydroxides
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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
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/485—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
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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
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/24—Electrodes for alkaline accumulators
- H01M4/26—Processes of manufacture
- H01M4/30—Pressing
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
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- 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
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- 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 precursor and a method for producing lithium titanate. Specifically, the present invention relates to a method for manufacturing lithium titanate that can be efficiently manufactured at low cost and is useful as a material for an electricity storage device. The present invention also relates to lithium titanate, an electrode active material containing the same, and an electricity storage device.
- Lithium titanate is being developed as a material for power storage devices, and is used as a negative electrode active material for power storage devices, particularly lithium secondary batteries, as an electrode active material with excellent safety and life characteristics.
- Lithium secondary batteries are rapidly spreading for small batteries such as portable device power supplies, and are also being developed for large-sized lithium secondary batteries for the electric power industry and automobiles. Electrode active materials for these large lithium secondary batteries are required to have long-term reliability and high input / output characteristics. Lithium titanate, which has excellent safety and life characteristics, is particularly promising for negative electrode active materials. Yes.
- lithium titanate there are several compounds as described in JP-A-6-275263 (Patent Document 1).
- Li x Ti y O 4 a compound in which 0.8 ⁇ x ⁇ 1.4 and 1.6 ⁇ y ⁇ 2.2 is described. Examples include LiTi 2 O 4 , Li 1.33 Ti 1.66 O 4, Li 0.8 Ti 2.2 O 4 , and the like.
- a wet method Japanese Patent Laid-Open No.
- Patent Document 2 in which a predetermined amount of a lithium compound and a titanium compound are mixed in a medium, dried and then fired, Among the wet methods, a spray drying method in which the drying is performed by spray drying (Japanese Patent Laid-Open No. 2001-192208: Patent Document 3), and a dry method in which a predetermined amount of a lithium compound and a titanium compound are mixed in a dry method and fired (Japanese Patent Laid-Open No. Hei. Japanese Patent Laid-Open No. 6-275263: Patent Document 1 and Japanese Patent Laid-Open No. 2000-302547: Patent Document 4) are known.
- Lithium titanate is produced by baking a lithium compound and a titanium compound also in the above-described dry method and wet method, but due to the solid phase diffusion reaction, the reactivity between these raw materials is low, and the target In addition to lithium titanate, by-products having different compositions and unreacted raw materials are likely to remain, and a sufficient electric capacity cannot be obtained when used in a battery. On the other hand, a higher firing temperature is advantageous in terms of reactivity, but lithium volatilization loss is likely to occur, and since lithium titanate particles shrink and sinter and grain growth proceeds, the specific surface area of lithium titanate particles And the rate characteristics are likely to deteriorate when used in a battery.
- a lithium titanate precursor (lithium A lithium titanate precursor by pulverizing at least a lithium compound and a titanium compound in a coexisting state in the production of a lithium titanate containing at least a compound and a titanium compound.
- a lithium titanate precursor lithium A lithium titanate precursor by pulverizing at least a lithium compound and a titanium compound in a coexisting state in the production of a lithium titanate containing at least a compound and a titanium compound.
- the characteristic configuration of the present invention is as follows. (1) A method for producing a lithium titanate precursor, comprising a step of pulverizing these compounds in a state where a lithium compound and a titanium compound coexist. (2) The pulverizing step includes adding a lithium titanate compound having the same crystal structure as the target lithium titanate in addition to the lithium compound and the titanium compound. Method for producing lithium acid precursor. (3) mixing a lithium compound and a titanium compound; A step of pulverizing these compounds in a state where the lithium compound and the titanium compound coexist by the mixing. Note that the mixing step and the pulverization step may be performed simultaneously, or the pulverization step may be performed after the mixing step.
- the method for producing a lithium titanate precursor according to (3) further comprising a step of pulverizing one of the lithium compound and the titanium compound prior to the mixing.
- the mixing step includes adding a lithium titanate compound having the same crystal structure as the target lithium titanate in addition to the lithium compound and the titanium compound,
- the pulverizing step includes pulverizing these compounds in the state where the lithium compound, the titanium compound, and the lithium titanate compound coexist, and the lithium titanate according to the above (3) or (4) A method for producing a precursor.
- (6) The method for producing a lithium titanate precursor according to any one of (1) to (5) above, wherein the pulverization is performed with an airflow pulverizer.
- (10) The method for producing a lithium titanate precursor according to any one of (7) to (9), wherein the pressure application step is performed under a condition that the bulk density of the mixed powder before pressure application is twice or more. .
- (11) A method for producing lithium titanate, comprising a step of heating a lithium titanate precursor obtained by the production method of any one of (1) to (10) above.
- (12) The method for producing lithium titanate as described in (11) above, wherein the heating temperature is 700 ° C. to 800 ° C.
- the method for producing lithium titanate according to the present invention at least a lithium compound and a titanium compound are pulverized in a state where they coexist to produce a lithium titanate precursor, whereby the reactivity between the titanium compound and the lithium compound is achieved.
- the target lithium titanate can be efficiently produced.
- the generation of subphases with different compositions and the remaining unreacted raw materials are small, and the intended lithium titanate with little progress of sintering and reduction in specific surface area is ensured even at a lower heating temperature than conventional production methods. Can be manufactured stably.
- lithium titanate manufactured by the above method when used as an electrode active material, an electricity storage device having excellent battery characteristics, particularly rate characteristics, can be manufactured.
- the reactivity between the lithium compound and the titanium compound can be further improved by producing a lithium titanate precursor by performing means for applying pressure to them simultaneously with and / or after the pulverization, and the precursor.
- a lithium titanate precursor by performing means for applying pressure to them simultaneously with and / or after the pulverization, and the precursor.
- the present invention relates to a method for producing a lithium titanate precursor which contains at least a titanium compound and a lithium compound and becomes lithium titanate by heating.
- the invention according to the first aspect is characterized by comprising a step of pulverizing these compounds in the state where the lithium compound and the titanium compound coexist.
- the invention according to the second aspect includes a step of mixing a lithium compound and a titanium compound, and a step of pulverizing these compounds in a state where the lithium compound and the titanium compound coexist by this mixing. It is characterized by.
- an inorganic titanium compound or an organic titanium compound such as titanium alkoxide can be used as the titanium compound.
- the inorganic titanium compound TiO (OH) 2 or TiO 2 ⁇ H metatitanic acid represented by 2 O, Ti (OH) 4 or titanate compounds such as ortho-titanate represented by TiO 2 ⁇ 2H 2 O, Titanium oxide (crystalline titanium oxide or amorphous titanium oxide such as rutile type, anatase type, brookite type, or bronze type), or a mixture thereof can be used.
- titanium oxide having an X-ray diffraction pattern having only a diffraction peak from a single crystal structure
- titanium oxide has a plurality of crystal structures such as those having an anatase type diffraction peak and a rutile type diffraction peak. It may have a diffraction peak.
- crystalline titanium oxide is preferable.
- the titanium compound is preferably fine in terms of reactivity with the lithium compound, and the average primary particle diameter (electron microscopy) is preferably in the range of 0.001 ⁇ m to 0.3 ⁇ m, and in the range of 0.005 ⁇ m to 0.3 ⁇ m. Is more preferable, the range of 0.01 ⁇ m to 0.3 ⁇ m is more preferable, and the range of 0.04 ⁇ m to 0.28 ⁇ m is even more preferable.
- the specific surface area is preferably greater value in terms of reactivity with the lithium compound of titanium compound is preferably 20 ⁇ 300m 2 / g, more preferably 50 ⁇ 300m 2 / g, 60 ⁇ 300m 2 / g is More preferred is 60 to 100 m 2 / g.
- the average secondary particle diameter is preferably 0.05 to 5 ⁇ m, more preferably 0.1 to 3.0 ⁇ m, More preferably, it is 0.5 to 2.0 ⁇ m.
- the titanium compound preferably has a high purity, and usually has a purity of 90% by weight or more, more preferably 99% by weight or more.
- the impurity Cl or SO 4 is preferably 0.5% by weight or less. Moreover, the following ranges are more preferable as other elements. Silicon (1000 ppm or less), calcium (1000 ppm or less), iron (1000 ppm or less), niobium (0.3 wt% or less), zirconium (0.2 wt% or less).
- lithium compound used in the present invention hydroxides, salts, oxides and the like can be used without particular limitation, and examples thereof include lithium hydroxide, lithium carbonate, lithium nitrate, lithium sulfate, and lithium oxide. These 1 type can be used and 2 or more types may be used together.
- lithium compounds lithium hydroxide, lithium carbonate, and lithium oxide are preferably used in order to avoid remaining acidic roots in lithium titanate, and lithium hydroxide and lithium carbonate are preferably used because of easy pulverization. More preferred is lithium carbonate.
- the acidic root means a sulfate group (SO 4 ) and a chlorine group (Cl).
- the lithium compound preferably has a high purity, and usually a purity of 98.0% by weight or more is good.
- Li 2 CO 3 is 98.0% by weight or more, preferably 99.0% by weight or more
- an impurity metal element such as Na, Ca, K, or Mg is present.
- 1000 ppm or less, preferably 500 ppm or less, and Cl and SO 4 are 1000 ppm or less, preferably 500 ppm or less.
- the volume average particle diameter of the lithium compound is not particularly limited, and generally available ones can be used. In the case of lithium carbonate, one having a volume average particle size in the range of 10 to 100 ⁇ m is common. Alternatively, the lithium compound may be refined alone in advance. When the volume average particle size is 5 ⁇ m or less, the miniaturization is preferable because the reactivity of the lithium titanate precursor is increased, and 4 ⁇ m or less is more preferable. A known method can be used for the refining treatment. Among them, the volume average particle size of the lithium compound is preferably 5 ⁇ m or less by pulverization, more preferably 0.5 to 5 ⁇ m, and even more preferably 1 to 5 ⁇ m. Further, the volume average particle diameter may be reduced to 4 ⁇ m or less, preferably in the range of 0.5 to 4 ⁇ m, more preferably in the range of 1 to 4 ⁇ m by pulverization.
- a known pulverizer can be used for the refining treatment, and examples include a flake crusher, a hammer mill, a pin mill, a bantam mill, a jet mill, a fret mill, a pan mill, an edge runner, a roller mill, a mix muller, and a vibration mill. .
- D90 cumulative frequency 90% diameter
- the thickness is preferably 7 ⁇ m or less.
- a high specific surface area is preferable because the reactivity of the lithium titanate precursor is increased.
- lithium carbonate 0.8 m 2 / g or more is preferable, and 1.0 to 3.0 m 2 / g is more preferable. preferable.
- pulverization is performed in a state where at least the titanium compound and the lithium compound coexist (hereinafter, this method may be referred to as “mixed pulverization”).
- this method may be referred to as “mixed pulverization”.
- both the titanium compound and the lithium compound may be charged into a pulverizer. Either one of the pulverizations may be started first, the other may be added later, both may be added and then pulverization may be started, and both may be mixed in advance using a known mixer such as a Henschel mixer. May be put into a pulverizer and pulverized.
- the degree of mixing of the titanium compound and the lithium compound becomes higher than when only the fine particles are mixed.
- a lithium titanate precursor containing a lithium compound and a titanium compound having a uniform particle size and a narrow particle size distribution can be obtained. Thereby, the lithium titanate precursor with high reactivity of a lithium compound and a titanium compound is obtained.
- pulverizers can be used for pulverization, for example, dry pulverizers such as flake crusher, hammer mill, pin mill, bantam mill, jet mill, fret mill, pan mill, edge runner, roller mill, mix muller, and vibration mill. preferable.
- dry pulverizers such as flake crusher, hammer mill, pin mill, bantam mill, jet mill, fret mill, pan mill, edge runner, roller mill, mix muller, and vibration mill.
- the use of an airflow pulverizer is preferable because the pulverization efficiency is high and the lithium compound can be miniaturized.
- the airflow crusher include a jet mill and a cyclone mill, and it is more preferable to use a jet mill.
- the titanium compound has a low bulk density, specifically, a bulk density in the range of 0.2 to 0.7 g / cm 3 , a highly reactive lithium titanate Since a precursor is obtained, it is preferable. It is considered that such a titanium compound having a low bulk density is easily dispersed on the air flow in the pulverizer and easily mixed with the lithium compound.
- the range of the bulk density is more preferably 0.2 to 0.6 g / cm 3 , further preferably 0.2 to 0.5 g / cm 3 .
- the lithium titanate precursor preferably has one peak in the frequency curve when the particle size distribution is measured in a state of being dispersed in ethanol.
- the volume average particle diameter is preferably 0.5 ⁇ m or less
- D90 (cumulative frequency 90% diameter) is preferably 10 ⁇ m or less
- the volume average particle diameter is 0.45 ⁇ m or less
- D90 (cumulative frequency 90% diameter). ) Is more preferably 6 ⁇ m or less.
- the pulverized product is bulky (low bulk density) and has a large occupied volume per mass, so that productivity, for example, throughput per unit time / equipment (material input amount) decreases. Therefore, when pressure is applied to the pulverized product, the bulkiness can be suppressed and an appropriate bulk density can be obtained.
- the pressure means is preferable because the titanium compound and the lithium compound are easily brought into contact with each other, and a lithium titanate precursor having a high reactivity between the lithium compound and the titanium compound is easily obtained.
- a means for applying pressure a means for forming by pressurization (compression), a means for pressurization (compression) and pulverization, or the like can be used. It is preferable that the bulk density is at least twice that before pressure is applied by means of applying pressure.
- a known pressure molding machine or compression molding machine can be used for the pressure (compression) molding of the mixed pulverized powder performed following the mixing and pulverizing step.
- a known pressure molding machine or compression molding machine can be used for example, a roller compactor, a roller crusher, a pellet molding machine, etc. Is mentioned.
- a pressure pulverizer, a compression pulverizer, and an attrition pulverizer can be used, and any pressure pulverizer, pan mill, edge runner, roller can be used as long as it can be pulverized by pressure and compression force.
- At least one pulverizer selected from a mill and a mix muller can be used.
- the pulverization principle of these pulverizers is to apply pressure to the sample and pulverize the sample with the high pressure. Taking the fret mill as an example, the operation state will be described. The sample under the roller is ground by rotating the heavy weight roller.
- a plurality of compounds are simultaneously mixed by being ground under a roller for a certain period of time.
- pressure can be applied to the mixed powder simultaneously with pulverization, and it is not necessary to provide a separate compression step, and the process can be simplified.
- the bulk density of the lithium titanate precursor preferably 0.2 ⁇ 0.7g / cm 3, more preferably 0.4 ⁇ 0.6g / cm 3.
- the bulk density is lower than the above range, the contact between the titanium compound and the lithium compound is small, the reactivity is lowered, and the productivity is also lowered. If it is higher than the above range, the gas generated during the reaction in the heating step will be difficult to escape or the heat conduction will be hindered. As a result, the single phase ratio of the lithium titanate obtained in any case is lowered.
- a lithium titanate precursor having a bulk density in the above range is easily obtained, and if it is less than 0.5 t / cm 2 Preferably, 0.15 to 0.45 t / cm 2 is more preferable.
- the lithium titanate precursor of the present invention may further contain a lithium titanate compound having the same crystal structure as the target lithium titanate.
- This lithium titanate compound is used as necessary, and is considered to suppress the sintering of the generated lithium titanate or act as a seed crystal. When this lithium titanate compound is used, it will be described later.
- the heating step can be performed at a relatively low temperature, and the particle growth of lithium titanate in the heating step is appropriately controlled, making it easy to produce the target lithium titanate. For this reason, it is necessary to have the same crystal structure as the target lithium titanate.
- the particle diameter of the lithium titanate compound is not particularly limited, and the same particle diameter (primary particle diameter calculated by electron microscopy) as the target lithium titanate, for example, An average particle size of about 0.5 to 2.0 ⁇ m may be used.
- the lithium titanate compound can be produced by the method of the present invention.
- the blending amount is preferably 1 to 30 parts by weight, more preferably 5 to 20 parts by weight, based on 100 parts by weight of the titanium compound as a raw material, in terms of Ti amount.
- a mixing aid or the like may be used for the lithium titanate precursor.
- the lithium titanate compound having the same crystal structure as that of the target lithium titanate may be contained in the titanium compound and / or the lithium compound before the pulverization of the titanium compound and the lithium compound, or may be included in the mixture before the pulverization. It is preferable to pulverize together with the titanium compound and the lithium compound by putting into a pulverizer during the pulverization, which may be added to the lithium titanate precursor after the pulverization, before or after applying pressure. It may be added after applying.
- various additives may be added to the lithium titanate precursor.
- carbon or a carbon compound that becomes a conductive material by heating described later may be added, and a grinding aid, a molding aid, or the like may be added.
- the lithium titanate precursor obtained by the above production method is heated to produce lithium titanate.
- the raw materials are placed in a heating furnace, The temperature is raised to a predetermined temperature and held for a certain time.
- a heating furnace it can carry out using a fluidized furnace, a stationary furnace, a rotary kiln, a tunnel kiln etc., for example.
- the heating temperature is preferably 700 ° C. or higher, and preferably 950 ° C. or lower.
- the temperature is lower than 700 ° C., the single phase ratio of the target lithium titanate is decreased, and the amount of unreacted titanium compound is increased.
- a preferable heating temperature is 700 ° C. to 800 ° C.
- heating at 800 ° C. or higher, preferably 900 ° C. or higher is required, but by using the lithium titanate precursor of the present invention, heating at 700 ° C. to 800 ° C. is also possible.
- the single phase rate is preferably 95% or more, more preferably 96% or more, and more preferably 97% or more.
- the heating time can be appropriately set, and about 3 to 6 hours is appropriate.
- the heating atmosphere is not limited, but is preferably an oxidizing atmosphere such as air or oxygen gas, a non-oxidizing atmosphere such as nitrogen gas or argon gas, or a reducing atmosphere such as hydrogen gas or carbon monoxide gas. Is preferred.
- the lithium titanate precursor has a high bulk density
- the resulting lithium titanate can be increased in bulk density, which contributes to an improvement in productivity.
- the lithium titanate thus obtained may be crushed or crushed as necessary after cooling.
- the above-mentioned known pulverizer can be used.
- the lithium titanate of the present invention is preferable because it has less sintering and grain growth, so that when pulverized and pulverized, the lithium titanate particles are easily broken and easily dispersed in a paste when an electrode of an electricity storage device is produced.
- the lithium titanate thus obtained has a large specific surface area, specifically 1.0 m 2 / g or more is preferable, 2.0 to 50.0 m 2 / g is more preferable, and 2.0 More preferred is 40.0 m 2 / g.
- the bulk density and average particle diameter of lithium titanate can be set as appropriate, and the bulk density is preferably 0.1 to 0.8 g / cm 3 , more preferably 0.2 to 0.7 g / cm 3. .
- the volume average particle diameter is preferably 1 to 10 ⁇ m.
- Specific surface area In the present specification, the specific surface area is measured by a BET single point method by nitrogen adsorption. As the apparatus, Monosorb manufactured by Yuasa Ionics or Monosorb model MS-22 manufactured by Quantachrome Instruments was used.
- the average particle diameter of the lithium compound means a volume average particle diameter measured by a laser diffraction method.
- the volume average particle size is determined by using a laser diffraction / scattering type particle size distribution measuring apparatus, using ethanol as the dispersion medium, setting the refractive index to 1.360 for ethanol, and appropriately setting the lithium compound according to the compound type. It is measured. For example, when the lithium compound is lithium carbonate, the refractive index is 1.500.
- LA-950 manufactured by Horiba Ltd. was used as a laser diffraction / scattering particle size distribution analyzer.
- the average particle size of the primary particles of the titanium compound is obtained by measuring the particle size of 100 primary particles in an image using a transmission electron microscope and taking the average value (electron microscopy). ).
- the average secondary particle diameter of the secondary particles of the titanium compound means a volume average particle diameter measured by a laser diffraction method.
- the volume average particle size is determined using a laser diffraction / scattering type particle size distribution measuring device, pure water is used as a dispersion medium, the refractive index is 1.333 for pure water, and the titanium compound is appropriately selected according to the type of compound. Set and measured. For example, when the titanium compound is anatase type titanium oxide, the refractive index is 2.520. LA-950 manufactured by Horiba Ltd. was used as the laser diffraction / scattering particle size distribution measuring apparatus.
- the average particle diameter of the lithium titanate precursor mixture refers to a volume average particle diameter measured by a laser diffraction method.
- the volume average particle size is determined by using a laser diffraction / scattering type particle size distribution measuring apparatus, using ethanol as a dispersion medium, a refractive index of 1.360 for ethanol, and the numerical value of the compounded lithium compound for the measurement particles. It was measured using. For example, when the lithium compound is lithium carbonate, the refractive index is 1.567.
- LA-950 manufactured by Horiba Ltd. was used as a laser diffraction / scattering particle size distribution measuring apparatus.
- the average particle size of primary particles of lithium titanate is obtained by measuring the particle size of 100 primary particles in an image using a transmission electron microscope and taking the average value (electron microscope). Law).
- the average secondary particle diameter of the secondary particle of lithium titanate means the volume average particle diameter measured by the laser diffraction method.
- the volume average particle size is determined by using a laser diffraction / scattering type particle size distribution measuring device, using pure water as a dispersion medium, a refractive index of 1.333 for water, and appropriately for lithium titanate depending on the compound type. Set and measure.
- the lithium titanate is Li 4 Ti 5 O 12
- the refractive index is 2.700.
- LA-950 manufactured by Horiba Ltd. was used as the laser diffraction / scattering particle size distribution measuring apparatus.
- the single phase ratio of lithium titanate is an index that is expressed by the following formula 1 and indicates the target content of lithium titanate.
- X is the main peak intensity of the target lithium titanate in powder X-ray diffraction measurement using Cuk ⁇ rays
- Yi is the main peak intensity of each subphase.
- the bulk density is determined by a cylinder type (a sample is put in a measuring cylinder and calculated from volume and mass).
- impurities such as sodium and potassium are measured by an atomic absorption method, SO 4 and chlorine are measured by an ion chromatography method or a fluorescent X-ray measuring device, and silicon, calcium, iron, chromium, nickel, manganese are measured. Other elements such as copper, zinc, aluminum, magnesium, niobium and zirconium are measured by the ICP method.
- a fluorescent X-ray measurement apparatus RIGAKU RIX-2200
- this invention is an electrode active material, Comprising: It contains the lithium titanate of this invention mentioned above, It is characterized by the above-mentioned.
- the present invention is an electricity storage device, characterized by using lithium titanate obtained by the above-described production method of the present invention.
- This electricity storage device includes an electrode, a counter electrode, a separator, and an electrolytic solution.
- the electrode is obtained by adding a conductive material and a binder to the electrode active material, and forming or applying the material appropriately.
- the conductive material include conductive assistants such as carbon black, acetylene black, and ketjen black.
- the binder examples include fluorine resins such as polytetrafluoroethylene, polyvinylidene fluoride, and fluorine rubber, and styrene butadiene rubber. Water-soluble resins such as carboxymethyl cellulose and polyacrylic acid.
- the electrode active material can be used as a positive electrode, and a lithium-containing metal, lithium alloy, or a carbon-containing material such as graphite can be used as a counter electrode.
- the electrode active material is used as a negative electrode, and a lithium / manganese composite oxide, a lithium / cobalt composite oxide, a lithium / nickel composite oxide, a lithium / cobalt / manganese / nickel composite oxide, or a lithium / vanadine composite oxide is used as the positive electrode.
- Lithium / transition metal composite oxides such as olivine, and olivine type compounds such as lithium / iron / composite phosphate compounds can be used.
- a porous polypropylene film or the like is used, and for the electrolyte, propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ⁇ -butyl lactone, 1,2-dimethoxyethane, etc.
- Conventional materials such as those obtained by dissolving lithium salts such as LiPF 6 , LiClO 4 , LiCF 3 SO 3 , LiN (CF 3 SO 2 ) 2 , LiBF 4 in the above solvent can be used.
- the lithium titanate of the present invention is used not only as an active material of a lithium secondary battery, but also attached to the surface of another type of active material, blended with an electrode, contained in a separator, or as a lithium ion conductor. You may use it. Moreover, you may use as an active material of a sodium ion battery.
- Example 1 Titanium oxide powder (Ishihara Sangyo Co., Ltd., purity 97.3%, volume average particle size 1.3 ⁇ m, specific surface area 93 m 2 / g, bulk density 0.3 g / cm 3 ) as titanium compound, and lithium carbonate as lithium compound
- the raw material was sampled so that the powder (purity 99.2%, volume average particle size 7.5 ⁇ m) was Li / Ti molar ratio of 0.81, and titanium having the same crystal structure as the target lithium titanate 5 parts by weight of lithium titanate (Li 4 Ti 5 O 12 , purity 99%, average particle size (electron microscopy) 1 ⁇ m) as a lithium acid compound was added to 100 parts by weight of a raw material, and a fret mill (grinding roller 40 kg, Mixing / pulverization / compression treatment was performed for 15 minutes at a roller rotation number of 50 rpm) to prepare a lithium titanate precursor.
- a fret mill grinding roller 40 kg, Mixing / pulverization
- the bulk density of this precursor was 0.6 g / cm 3, the volume average particle size was 0.4 ⁇ m, D90 was 6.2 ⁇ m, and the frequency distribution had a single peak in the frequency curve.
- the lithium titanate precursor was heated in the atmosphere at 750 ° C. for 3 hours using an electric furnace to synthesize lithium titanate.
- the obtained lithium titanate was crushed with a jet mill to obtain Sample 1.
- the resulting sample 1 had a bulk density of 0.6 g / cm 3 .
- the bulk density was calculated from the volume and mass of a sample placed in a measuring cylinder.
- the specific surface area (BET 1-point method nitrogen adsorption, Monosorb model MS-22 manufactured by Quantachrome Instruments) was 5 m 2 / g.
- the particle size distribution of the lithium titanate precursor was measured using a laser diffraction / scattering type particle size distribution measuring device (LA-950, manufactured by HORIBA, Ltd.).
- the refractive index was 1.360 for the dispersion medium, and for the measured particles. Measurements were made at 1.567.
- Example 2 Titanium oxide powder (Ishihara Sangyo Co., Ltd., purity 97.3%, volume average particle size 1.3 ⁇ m, specific surface area 93 m 2 / g, bulk density 0.3 g / cm 3 ) as titanium compound, and lithium carbonate as lithium compound
- the raw material was sampled so that the powder (purity 99.2%, volume average particle size 7.5 ⁇ m) was Li / Ti molar ratio of 0.81, and titanium having the same crystal structure as the target lithium titanate 5 parts by weight of lithium titanate (Li 4 Ti 5 O 12 , purity 99%, average particle size (electron microscopy) 1 ⁇ m) as a lithium acid compound was added to 100 parts by weight of the raw material, and for 5 minutes in a Henschel mixer, Mix at 1020 rpm.
- the mixed powder was pulverized by a jet mill (STJ-200 manufactured by Seishin Enterprise Co., Ltd.).
- This powder had a volume average particle size of 0.4 ⁇ m, D90 of 2.2 ⁇ m, and a single frequency curve peak of the particle size distribution.
- the bulk density was 0.3 g / cm 3 .
- pressure compression pressure 0.4 ton / cm 2
- WP 160 ⁇ 60 manufactured by Freund Turbo was applied with a roller compactor (WP 160 ⁇ 60 manufactured by Freund Turbo) to prepare a lithium titanate precursor.
- the bulk density of this precursor was 0.7 g / cm 2 .
- the lithium titanate precursor was heated in the atmosphere at 750 ° C. for 3 hours using an electric furnace to synthesize lithium titanate.
- the obtained lithium titanate was crushed with a jet mill to obtain Sample 2.
- the obtained sample 2 had a bulk density of 0.6 g / cm 3 .
- Example 3 Titanium oxide powder (Ishihara Sangyo Co., Ltd., purity 97.3%, volume average particle size 1.3 ⁇ m, specific surface area 93 m 2 / g) as titanium compound, and lithium carbonate powder (purity 99.2%, volume) as lithium compound
- the raw material was sampled so that the average particle size 7.5 ⁇ m was 0.81 in terms of Li / Ti molar ratio, and lithium titanate (Li) as a lithium titanate compound having the same crystal structure as the target lithium titanate.
- Comparative Example 1 Titanium oxide powder (Ishihara Sangyo Co., Ltd., purity 97.3%, volume average particle size 1.3 ⁇ m, specific surface area 93 m 2 / g, bulk density 0.3 g / cm 3 ) as titanium compound, and lithium carbonate as lithium compound
- the raw material was sampled so that the powder (purity 99.2%, volume average particle size 7.5 ⁇ m) was Li / Ti molar ratio of 0.81, and titanium having the same crystal structure as the target lithium titanate 5 parts by weight of lithium titanate (Li 4 Ti 5 O 12 , purity 99%, average particle size (electron microscopy) 1 ⁇ m) as a lithium acid compound was added to 100 parts by weight of the raw material, and 10 minutes in a Henschel mixer, Mixing at 1800 rpm produced a lithium titanate precursor.
- the bulk density of this precursor was 0.3 g / cm 3 , the volume average particle size was 0.9 ⁇ m, D90 was 15.2 ⁇ m, and two peaks were observed in the frequency curve of the particle size distribution.
- the obtained lithium titanate precursor was heated in the atmosphere at 750 ° C. for 3 hours using an electric furnace to synthesize lithium titanate.
- the obtained lithium titanate was crushed with a jet mill to obtain Sample 4.
- the bulk density of the obtained sample 4 was 0.3 g / cm 3 .
- Comparative Example 2 In Comparative Example 1, a titanium titanate precursor was prepared by applying pressure (compression pressure 0.4 ton / cm 2 ) to the lithium titanate precursor with a roller compactor. Lithium acid (sample 5) was synthesized. The bulk density of this precursor was 0.6 g / cm 3 , and the bulk density of Sample 5 was 0.6 g / cm 3 .
- the powder X-ray diffraction measurement results of Samples 1 and 4 are shown in FIG. Sample 3 using a lithium titanate precursor prepared by pulverizing at least in a lithium compound and a titanium compound, and means for pulverizing in a state in which they are present in at least a lithium compound and a titanium compound
- the single phase ratio is 95% or more even when heated at 750 ° C.
- Lithium titanate Li4Ti5O12 was obtained, while at least sample 4 using a lithium titanate precursor prepared by mixing only at least lithium compound and titanium compound without performing pulverization in the coexistence state of them, at least Pressure is not applied to the lithium compound and titanium compound without pulverization in the presence of them.
- Sample 5 Using lithium titanate precursor prepared by performing only means for applying the, in heating at 750 ° C. Li Li 4 Ti 5 O 12 titanate single phase ratio of 95% or more was not Tokura. From this, it can be seen that the production method of the present invention makes it possible to synthesize lithium titanate having a single phase ratio of 95% or more even when the heating temperature during lithium titanate synthesis is low, specifically, less than 800 ° C.
- This working electrode was vacuum-dried at 120 ° C. for 4 hours, and then incorporated as a positive electrode in a sealable coin-type cell in a glove box having a dew point of ⁇ 70 ° C. or lower.
- As the negative electrode a metal lithium having a thickness of 0.5 mm formed into a circle having a diameter of 12 mm was used.
- As the non-aqueous electrolyte a mixed solution of ethylene carbonate and dimethyl carbonate (mixed in a volume ratio of 1: 2) in which LiPF 6 was dissolved at a concentration of 1 mol / liter was used.
- the working electrode was placed in a lower can of a coin-type cell, a porous polypropylene film was placed thereon as a separator, and a non-aqueous electrolyte was dropped thereon. Furthermore, a negative electrode, a 0.5 mm thickness spacer for adjusting the thickness, and a spring (both made of SUS316) are placed thereon, and an upper can with a polypropylene gasket is put on the outer peripheral edge to seal and sealed. An electricity storage device (sample A) was obtained.
- An electricity storage device (samples B and C) was obtained in the same manner as the electricity storage device of sample A, except that sample 2 or 4 was used instead of sample 1 as lithium titanate.
- (2) Evaluation of rate characteristics For the electricity storage devices (samples A to C) produced above, the discharge capacity was measured with various amounts of current, and the capacity retention rate (%) was calculated. The measurement was performed by setting the voltage range to 1 to 3 V, the charging current to 0.25 C, and the discharging current to 0.25 C to 30 C. The environmental temperature was 25 ° C.
- the capacity retention rate was calculated by the formula of (Xn / X0.25) ⁇ 100, where X0.25 is the measured value of the discharge capacity at 0.25 C and Xn is the measured value in the range of 0.5 C to 30 C. .
- 1 C means a current value that can be fully charged in one hour, and 0.48 mA corresponds to 1 C in this evaluation.
- Table 1 It turns out that the electrical storage device (sample A, B) of this invention is excellent in the rate characteristic compared with the comparative example (sample C).
- the target lithium titanate of the present invention can be reliably and stably produced at a low cost and at a heating temperature lower than that of the conventional production method.
- lithium titanate manufactured by the above method when used as an electrode active material, an electricity storage device having excellent battery characteristics, particularly rate characteristics, can be manufactured.
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Abstract
Description
(1)リチウム化合物およびチタン化合物が共存している状態で、これらの化合物を粉砕するステップを備える、チタン酸リチウム前駆体の製造方法。
(2)前記粉砕ステップは、前記リチウム化合物および前記チタン化合物に加えて、目的とするチタン酸リチウムと同じ結晶構造を有するチタン酸リチウム化合物を添加することを含む、上記(1)に記載のチタン酸リチウム前駆体の製造方法。
(3)リチウム化合物およびチタン化合物を混合するステップと、
前記混合によって前記リチウム化合物および前記チタン化合物が共存している状態で、これらの化合物を粉砕するステップとを備える、チタン酸リチウム前駆体の製造方法。なお、混合ステップと粉砕ステップとを同時に行っても良いし、混合ステップの後に粉砕ステップを行うようにしても良い。
(4)前記混合に先立ち、リチウム化合物およびチタン化合物のいずれか一方に対して粉砕処理を行うステップをさらに備える、上記(3)に記載のチタン酸リチウム前駆体の製造方法。
(5)前記混合ステップは、前記リチウム化合物および前記チタン化合物に加えて、目的とするチタン酸リチウムと同じ結晶構造を有するチタン酸リチウム化合物を添加することを含み、
前記粉砕ステップは、前記リチウム化合物、前記チタン化合物および前記チタン酸リチウム化合物が共存している状態で、これらの化合物を粉砕することを含む、上記(3)または(4)に記載のチタン酸リチウム前駆体の製造方法。
(6)前記粉砕を気流粉砕機で行う、上記(1)~(5)のいずれかに記載のチタン酸リチウム前駆体の製造方法。
(7)前記粉砕と同時に及び/又は粉砕後に、混合状態の化合物に圧力を付与するステップをさらに備える、上記(1)~(6)のいずれかに記載のチタン酸リチウム前駆体の製造方法。
(8)前記圧力の付与を圧縮成形機により行う、上記(7)に記載のチタン酸リチウム前駆体の製造方法。
(9)前記粉砕および前記圧力の付与を、フレットミル、パンミル、エッジランナー、ローラーミルおよびミックスマーラーからなる群から選ばれた少なくとも一種の機械で行う、上記(7)に記載のチタン酸リチウム前駆体の製造方法。
(10)前記圧力付与ステップは、圧力付与前の混合粉末の嵩密度を2倍以上とする条件で行う、上記(7)~(9)のいずれかに記載のチタン酸リチウム前駆体の製造方法。
(11)上記(1)~(10)のいずれかの製造方法で得られるチタン酸リチウム前駆体を加熱するステップを備える、チタン酸リチウムの製造方法。
(12)前記加熱温度が700℃~800℃である、上記(11)に記載のチタン酸リチウムの製造方法。
(13)上記(11)または(12)に記載の製造方法で得られたチタン酸リチウム。
(14)上記(13)に記載のチタン酸リチウムを含む電極活物質。
(15)上記(13)に記載のチタン酸リチウムを用いた蓄電デバイス。
本願明細書において、比表面積は、窒素吸着によるBET一点法にて測定したものである。装置はユアサアイオニクス社製モノソーブ又はQuantachrome Instruments社製Monosorb型番MS-22を用いた。
本願明細書において、リチウム化合物の平均粒径とは、レーザー回折法で測定した体積平均粒径をいう。体積平均粒径は、レーザー回折/散乱式粒度分布測定装置を用い、分散媒にエタノールを使用し、屈折率をエタノールについては1.360とし、リチウム化合物については化合物種に応じて適宜設定して測定したものである。例えば、リチウム化合物が炭酸リチウムである場合、屈折率は1.500を使用する。レーザー回折/散乱式粒度分布測定装置としては、堀場製作所社製 LA-950を用いた。
本願明細書において、チタン化合物の一次粒子の平均粒径は、透過型電子顕微鏡を用い、画像中の一次粒子100個の粒子径を測定し、その平均値を取ったものである(電子顕微鏡法)。
本願明細書において、チタン酸リチウム前駆体混合物の平均粒径とは、レーザー回折法で測定した体積平均粒径をいう。体積平均粒径は、レーザー回折/散乱式粒度分布測定装置を用い、分散媒にエタノールを使用し、屈折率を、エタノールについては1.360とし、測定粒子については配合したリチウム化合物種の数値を用いて測定したものである。例えば、リチウム化合物が炭酸リチウムである場合は、屈折率は1.567を使用する。レーザー回折/散乱式粒度分布測定装置は、堀場製作所社製 LA-950を用いた。
本願明細書において、チタン酸リチウムの一次粒子の平均粒径は、透過型電子顕微鏡を用い、画像中の一次粒子100個の粒子径を測定し、その平均値を取ったものである(電子顕微鏡法)。
本願明細書において、チタン酸リチウムの単相率とは、下記式1で表され、目的とするチタン酸リチウムの含有率を示す指標である。
(式1)単相率(%)=100×(1-Σ(Yi/X))
ここで、Xは、Cukα線を用いた粉末X線回折測定における、目的とするチタン酸リチウムのメインピーク強度、Yiは各副相のメインピーク強度である。Li4Ti5O12の場合、Xは2θ=18°付近のピーク強度であり、アナターゼ型又はルチル型TiO2やLi2TiO3が副相として存在しやすいのでYiには2θ=25°付近のピーク強度(アナターゼ型TiO2)、2θ=27°付近のピーク強度(ルチル型TiO2)と2θ=44°付近のピーク強度(Li2TiO3)を用いる。
本願明細書において、嵩密度は、シリンダー式(メスシリンダに試料を入れ、体積と質量から算出)により求める。
本願明細書において、不純物である、ナトリウム、カリウムは原子吸光法により測定し、SO4、塩素はイオンクロマトグラフィー法又は蛍光X線測定装置により測定し、ケイ素、カルシウム、鉄、クロム、ニッケル、マンガン、銅、亜鉛、アルミニウム、マグネシウム、ニオブ、ジルコニウムなどのその他の元素はICP法により測定する。SO4については、蛍光X線測定装置(RIGAKU RIX-2200)を用いた。
チタン化合物として酸化チタン粉末(石原産業株式会社製、純度97.3%、体積平均粒径1.3μm、比表面積93m2/g、嵩密度0.3g/cm3)と、リチウム化合物として炭酸リチウム粉末(純度99.2%、体積平均粒径7.5μm)をLi/Tiモル比で0.81となるように原料を採取し、更に、目的とするチタン酸リチウムと同じ結晶構造を有するチタン酸リチウム化合物としてチタン酸リチウム(Li4Ti5O12、純度99%、平均粒径(電子顕微鏡法)1μm)を原料100重量部に対して5重量部添加し、フレットミル(粉砕ローラー40kg、ローラー回転数50rpm)にて混合/粉砕/圧縮処理を15分行い、チタン酸リチウム前駆体を作製した。この前駆体の嵩密度は0.6g/cm3であり、体積平均粒径は0.4μm、D90は6.2μm、粒度分布の頻度曲線のピークは一つであった。次いで、チタン酸リチウム前駆体を、電気炉を用い大気中750℃で3時間加熱し、チタン酸リチウムを合成した。得られたチタン酸リチウムをジェットミルで解砕し、試料1を得た。得られた試料1の嵩密度は0.6g/cm3であった。嵩密度は、メスシリンダに試料を入れ、体積と質量から算出した。比表面積(BET1点法 窒素吸着、Quantachrome Instruments社製Monosorb 型番MS-22)は5m2/gであった。チタン酸リチウム前駆体の粒度分布の測定には、レーザー回折/散乱式粒度分布測定装置(堀場製作所社製 LA-950)を用い、屈折率は、分散媒については1.360、測定粒子については1.567に設定して測定した。
チタン化合物として酸化チタン粉末(石原産業株式会社製、純度97.3%、体積平均粒径1.3μm、比表面積93m2/g、嵩密度0.3g/cm3)と、リチウム化合物として炭酸リチウム粉末(純度99.2%、体積平均粒径7.5μm)をLi/Tiモル比で0.81となるように原料を採取し、更に、目的とするチタン酸リチウムと同じ結晶構造を有するチタン酸リチウム化合物としてチタン酸リチウム(Li4Ti5O12、純度99%、平均粒径(電子顕微鏡法)1μm)を原料100重量部に対して5重量部添加し、ヘンシェル混合器で5分間、1020rpmで混合した。次いで、この混合粉に、ジェットミル(セイシン企業社製 STJ-200)にて粉砕処理を行った。この粉末の体積平均粒径は0.4μm、D90は2.2μm、粒度分布の頻度曲線のピークは一つであった。また、嵩密度は0.3g/cm3であった。粉砕処理後、ローラーコンパクター(フロイントターボ社製 WP160×60)にて圧力(圧縮圧0.4ton/cm2)をかけてチタン酸リチウム前駆体を作製した。この前駆体の嵩密度は0.7g/cm2であった。次いで、当該チタン酸リチウム前駆体を、電気炉を用い大気中750℃で3時間加熱し、チタン酸リチウムを合成した。得られたチタン酸リチウムをジェットミルで解砕し、試料2を得た。得られた試料2の嵩密度は0.6g/cm3であった。
チタン化合物として酸化チタン粉末(石原産業株式会社製、純度97.3%、体積平均粒径1.3μm、比表面積93m2/g)と、リチウム化合物として炭酸リチウム粉末(純度99.2%、体積平均粒径7.5μm)をLi/Tiモル比で0.81となるように原料を採取し、更に、目的とするチタン酸リチウムと同じ結晶構造を有するチタン酸リチウム化合物としてチタン酸リチウム(Li4Ti5O12、純度99%、平均粒径(電子顕微鏡法)1μm)を原料100重量部に対して5重量部添加し、ヘンシェル混合器で5分間、1020rpmで混合した。次いで、この混合粉にジェットミルにて粉砕処理を行い、チタン酸リチウム前駆体を作製した。この前駆体の嵩密度は0.3g/cm3、体積平均粒径は0.4μm、D90は2.2μmで粒度分布の頻度曲線のピークは一つであった。次いで、当該チタン酸リチウム前駆体を、電気炉を用い大気中750℃で3時間加熱し、チタン酸リチウムを合成した。得られたチタン酸リチウムをジェットミルで解砕し、試料3を得た。得られた試料3の嵩密度は0.3g/cm3であった。
チタン化合物として酸化チタン粉末(石原産業株式会社製、純度97.3%、体積平均粒径1.3μm、比表面積93m2/g、嵩密度0.3g/cm3)と、リチウム化合物として炭酸リチウム粉末(純度99.2%、体積平均粒径7.5μm)をLi/Tiモル比で0.81となるように原料を採取し、更に、目的とするチタン酸リチウムと同じ結晶構造を有するチタン酸リチウム化合物としてチタン酸リチウム(Li4Ti5O12、純度99%、平均粒径(電子顕微鏡法)1μm)を原料100重量部に対して5重量部添加し、ヘンシェル混合器で10分間、1800rpmで混合し、チタン酸リチウム前駆体を作製した。この前駆体の嵩密度は0.3g/cm3、体積平均粒径は0.9μm、D90は15.2μmで、粒度分布の頻度曲線には二つのピークが認められた。次いで、得られたチタン酸リチウム前駆体を、電気炉を用い大気中750℃で3時間加熱し、チタン酸リチウムを合成した。得られたチタン酸リチウムをジェットミルで解砕し、試料4を得た。得られた試料4の嵩密度は0.3g/cm3であった。
比較例1において、チタン酸リチウム前駆体に、更にローラーコンパクターにて圧力(圧縮圧0.4ton/cm2)をかけてチタン酸リチウム前駆体を作製した以外は、比較例1と同様にしてチタン酸リチウム(試料5)を合成した。この前駆体の嵩密度は0.6g/cm3であり、試料5の嵩密度は0.6g/cm3であった。
得られた試料1~5について、粉末X線回折装置(リガク社製 UltimaIV Cukα線使用)を用いて粉末X線回折パターンを測定した。測定されたピーク強度のうち、Xとして、2θ=18°付近のLi4Ti5O12のピーク強度を、Yとして2θ=25°付近のアナターゼ型TiO2のピーク強度を用いて前述の単相率を算出したところ、単相率はそれぞれ、試料1:96%、試料2:98%、試料3:96%、試料4:93%、試料5:90%であった。なお、2θ=27°付近のルチル型TiO2のピーク及び2θ=44°付近のLi2TiO3のピークは観察されなかった。代表例として、試料1及び4の粉末X線回折測定結果を図1に示す。少なくともリチウム化合物及びチタン化合物に、それらが共存した状態で粉砕を行って調製したチタン酸リチウム前駆体を用いた試料3と、少なくともリチウム化合物及びチタン化合物に、それらが共存した状態で粉砕を行う手段と、前記粉砕と同時に及び/又は粉砕後に、それらに圧力をかける手段を行って調製したチタン酸リチウム前駆体を用いた試料1及び試料2では、750℃の加熱でも単相率95%以上のチタン酸リチウムLi4Ti5O12が得られたのに対し、少なくともリチウム化合物及びチタン化合物に、それらが共存した状態で粉砕を行う手段を行なわず混合のみで調製したチタン酸リチウム前駆体を用いた試料4、少なくともリチウム化合物及びチタン化合物に、それらが共存した状態で粉砕を行う手段を行なわず圧力をかける手段のみを行って調製したチタン酸リチウム前駆体を用いた試料5では、750℃での加熱では単相率が95%以上のチタン酸リチウムLi4Ti5O12は得らなかった。このことから、本発明の製造方法により、チタン酸リチウム合成時の加熱温度が低くても、具体的には800℃未満でも、単相率が95%以上のチタン酸リチウムを合成できることがわかる。
電池特性の評価
(1)蓄電デバイスの作成
試料1のチタン酸リチウムと、導電剤としてのアセチレンブラック粉末、及び結着剤としてのポリフッ化ビニリデン樹脂を重量比で100:5:7で混合し、乳鉢で練り合わせ、ペーストを調製した。このペーストをアルミ箔上に塗布し、120℃の温度で10分乾燥した後、直径12mmの円形に打ち抜き、17MPaでプレスして作用極とした。電極中に含まれる活物質量は、3mgであった。
(2)レート特性の評価
上記で作製した蓄電デバイス(試料A~C)について、種々の電流量で放電容量を測定して容量維持率(%)を算出した。測定は、電圧範囲を1~3Vに、充電電流は0.25Cに、放電電流は0.25C~30Cの範囲に設定して行った。環境温度は25℃とした。容量維持率は、0.25Cでの放電容量の測定値をX0.25、0.5C~30Cの範囲での測定値をXnとすると、(Xn/X0.25)×100の式で算出した。尚、ここで1Cとは、1時間で満充電できる電流値を言い、本評価では、0.48mAが1Cに相当する。容量維持率が高いほうが、レート特性が優れている。結果を、表1に示す。本発明の蓄電デバイス(試料A,B)は、比較例(試料C)に比べて、レート特性に優れていることが判る。
Claims (15)
- リチウム化合物およびチタン化合物が共存している状態で、これらの化合物を粉砕するステップを備える、チタン酸リチウム前駆体の製造方法。
- 前記粉砕ステップは、前記リチウム化合物および前記チタン化合物に加えて、目的とするチタン酸リチウムと同じ結晶構造を有するチタン酸リチウム化合物を添加することを含む、請求項1に記載のチタン酸リチウム前駆体の製造方法。
- リチウム化合物およびチタン化合物を混合するステップと、
前記混合によって前記リチウム化合物および前記チタン化合物が共存している状態で、これらの化合物を粉砕するステップとを備える、チタン酸リチウム前駆体の製造方法。 - 前記混合に先立ち、リチウム化合物およびチタン化合物のいずれか一方に対して粉砕処理を行うステップをさらに備える、請求項3に記載のチタン酸リチウム前駆体の製造方法。
- 前記混合ステップは、前記リチウム化合物および前記チタン化合物に加えて、目的とするチタン酸リチウムと同じ結晶構造を有するチタン酸リチウム化合物を添加することを含み、
前記粉砕ステップは、前記リチウム化合物、前記チタン化合物および前記チタン酸リチウム化合物が共存している状態で、これらの化合物を粉砕することを含む、請求項3に記載のチタン酸リチウム前駆体の製造方法。 - 前記粉砕を気流粉砕機で行う、請求項1または3に記載のチタン酸リチウム前駆体の製造方法。
- 前記粉砕と同時に及び/又は粉砕後に、混合状態の化合物に圧力を付与するステップをさらに備える、請求項1または3に記載のチタン酸リチウム前駆体の製造方法。
- 前記圧力の付与を圧縮成形機により行う、請求項7に記載のチタン酸リチウム前駆体の製造方法。
- 前記粉砕および前記圧力の付与を、フレットミル、パンミル、エッジランナー、ローラーミルおよびミックスマーラーからなる群から選ばれた少なくとも一種の機械で行う、請求項7に記載のチタン酸リチウム前駆体の製造方法。
- 前記圧力付与ステップは、圧力付与前の混合粉末の嵩密度を2倍以上とする条件で行う、請求項7に記載のチタン酸リチウム前駆体の製造方法。
- 請求項1または3に記載の製造方法で得られるチタン酸リチウム前駆体を加熱するステップを備える、チタン酸リチウムの製造方法。
- 前記加熱温度が700℃~800℃である、請求項11に記載のチタン酸リチウムの製造方法。
- 請求項11の製造方法で得られたチタン酸リチウム。
- 請求項13に記載のチタン酸リチウムを含む電極活物質。
- 請求項13に記載のチタン酸リチウムを用いた蓄電デバイス。
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EP12776557.6A EP2703354A4 (en) | 2011-04-28 | 2012-04-26 | METHOD FOR MANUFACTURING LITHIUM TITANATE PRECURSOR, METHOD FOR MANUFACTURING LITHIUM TITANATE, LITHIUM TITANATE, ELECTRODE ACTIVE SUBSTANCE, AND STORAGE DEVICE |
CN201280009219.7A CN103429536B (zh) | 2011-04-28 | 2012-04-26 | 钛酸锂前驱物的制造方法、钛酸锂的制造方法、钛酸锂、电极活性物质及蓄电装置 |
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CN103429536B (zh) | 2017-05-10 |
TWI564248B (zh) | 2017-01-01 |
US9428396B2 (en) | 2016-08-30 |
KR101907082B1 (ko) | 2018-10-11 |
CN103429536A (zh) | 2013-12-04 |
US20140048968A1 (en) | 2014-02-20 |
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