Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/36—Selection of substances as active materials, active masses, active liquids
  • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
  • H01M4/485—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
  • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
  • C01G23/00—Compounds of titanium
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/05—Accumulators with non-aqueous electrolyte
  • H01M10/052—Li-accumulators
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/05—Accumulators with non-aqueous electrolyte
  • H01M10/052—Li-accumulators
  • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/05—Accumulators with non-aqueous electrolyte
  • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
  • H01M10/0561—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of inorganic materials only
  • H01M10/0562—Solid materials
• • 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
  • H01M10/058—Construction or manufacture
  • H01M10/0585—Construction or manufacture of accumulators having only flat construction elements, i.e. flat positive electrodes, flat negative electrodes and flat separators
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
  • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/36—Selection of substances as active materials, active masses, active liquids
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/36—Selection of substances as active materials, active masses, active liquids
  • H01M4/362—Composites
  • H01M4/366—Composites as layered products
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
  • H01M2004/027—Negative electrodes
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M2300/00—Electrolytes
  • H01M2300/0017—Non-aqueous electrolytes
  • H01M2300/0065—Solid electrolytes
  • H01M2300/0068—Solid electrolytes inorganic
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/10—Energy storage using batteries

Definitions

• the present invention relates to a negative electrode active material composition using lithium titanate powder suitable as a negative electrode material for all-solid secondary batteries, and to all-solid secondary batteries.
• lithium batteries have been widely used for small electronic devices such as mobile phones and laptop computers, electric vehicles, and power storage.
• the term lithium battery is used as a concept including so-called lithium ion secondary batteries.
• Lithium batteries currently on the market mainly consist of positive and negative electrodes containing materials capable of intercalating and deintercalating lithium, and a non-aqueous electrolyte consisting of a lithium salt and a non-aqueous solvent.
• the non-aqueous solvent is ethylene carbonate (EC ), propylene carbonate (PC) and other cyclic carbonates, and dimethyl carbonate (DMC), diethyl carbonate (DEC) and other chain carbonates.
• EC ethylene carbonate
• PC propylene carbonate
• DMC dimethyl carbonate
• DEC diethyl carbonate
• Lithium batteries use an electrolyte that contains flammable organic solvents, so they are prone to leaks and may ignite when shorted. A short-circuit prevention structure is required. Under such circumstances, all-solid secondary batteries using inorganic solid electrolytes instead of organic electrolytes have attracted attention.
• the positive electrode, negative electrode, and electrolyte of all-solid-state secondary batteries are all solid, they have the potential to greatly improve safety and reliability, which are problems of batteries using organic electrolytes, and also simplify safety devices. Since it is possible to increase the energy density, it is expected to be applied to electric vehicles and large storage batteries.
• all-solid-state secondary batteries form a good solid-solid interface from the viewpoint of realizing excellent ionic conductivity and long-term cycle characteristics, and Continuing maintenance is very important.
• Lithium titanate has attracted attention for maintaining a good interface between the active material and the solid electrolyte. Lithium titanate is expected to maintain the interface between the active material and the solid electrolyte for a long period of time during charge/discharge because the volume change due to charge/discharge is very small.
• Patent Document 1 discloses an electrode using lithium titanate having a specific BET specific surface area and solid electrolyte particles smaller than the average particle size of the lithium titanate, and the contact between the lithium titanate and the solid electrolyte particles is It is reported to be better than before.
• the specific surface area is 4 m 2 /g or more, boron (B), Ln (Ln is at least one metal element selected from the lanthanide element group, Y, and Sc), and containing at least one localization element selected from M1 (M1 is at least one metal element selected from W and Mo), boron (B) as the localization element, the Ln, and the A lithium titanate powder is disclosed in which M1 is localized in the vicinity of the surface of lithium titanate particles constituting the lithium titanate powder.
• Patent Document 2 discloses a lithium titanate powder that, when applied as an electrode material for an electricity storage device, has a large charge/discharge capacity and can suppress the amount of gas generated during high-temperature operation.
• the present invention provides a negative electrode active material composition that forms a good solid-solid interface with a solid electrolyte regardless of the particle size of the lithium titanate powder, and that can form a dense negative electrode layer with fewer voids than conventional ones. and an all-solid-state secondary battery.
• the inventors of the present invention have conducted research to further increase the contact area between the lithium titanate particles and the solid electrolyte even when lithium titanate powder having a relatively small average particle size is used. We found that by allowing a specific metal element to exist on the surface of the particles, the lithium titanate powder and the solid electrolyte form a good solid-solid interface, and that a dense negative electrode layer with fewer pores than before can be obtained. We have completed the present invention. By using the negative electrode active material composition containing the lithium titanate powder and the solid electrolyte in an all-solid secondary battery, the initial discharge capacity can be increased and the charge rate characteristics can be improved.
• Patent Document 2 does not describe or suggest at all the effect of increasing the density of the negative electrode layer containing the negative electrode active material and the solid electrolyte in the all-solid secondary battery.
• the present invention relates to a negative electrode active material composition using lithium titanate powder suitable as a negative electrode material for all-solid secondary batteries, and to all-solid secondary batteries.
• the present invention provides the following (1) to (9).
• An all-solid secondary battery comprising a positive electrode layer, a negative electrode layer and a solid electrolyte layer, wherein the negative electrode layer comprises the negative electrode active material composition according to any one of (1) to (8) above.
• An all-solid secondary battery that is a layer containing.
• a negative electrode active material composition and an all-solid secondary battery having excellent initial efficiency and charge rate characteristics can be obtained.
• the present invention relates to a negative electrode active material composition using lithium titanate powder suitable as a negative electrode material for all-solid secondary batteries, and to all-solid secondary batteries.
• a negative electrode active material composition of the present invention includes a lithium titanate powder containing Li 4 Ti 5 O 12 as a main component, and an inorganic solid electrolyte having conductivity of metal ions belonging to Group 1 of the periodic table.
• An active material composition At least one metal element selected from Al, W, Ce and Mo is present on the surface of the lithium titanate particles constituting the lithium titanate powder.
• the lithium titanate powder of the present invention contains Li 4 Ti 5 O 12 as a main component, and contains a crystalline component and/or an amorphous component other than Li 4 Ti 5 O 12 to the extent that the effects of the present invention can be obtained. can be done.
• the term "main component" means that the main peak of Li 4 Ti 5 O 12 accounts for 90% or more of the diffraction peaks measured by the X-ray diffraction method.
• the ratio of the intensity of the main peak of Li 4 Ti 5 O 12 is preferably 92% or more, and is 95% or more.
• the component other than Li 4 Ti 5 O 12 is the sum of the intensity of the main peak due to the crystalline component and the maximum intensity of the halo pattern due to the amorphous component.
• the lithium titanate powder of the present invention is composed of anatase-type titanium dioxide, rutile-type titanium dioxide, and lithium titanates having different chemical formulas, Li 2 TiO 3 , Li 0 . 6 Ti 3.4 O 8 , etc. may be included as the crystalline component.
• the lower the proportion of crystalline components other than Li 4 Ti 5 O 12 , particularly Li 0.6 Ti 3.4 O 8 the better the charging characteristics and charge/discharge capacity of the electricity storage device. can be improved.
• the intensity of the main peak of Li 4 Ti 5 O 12 is 100
• the intensity of the main peak of anatase-type titanium dioxide and the main peak intensity of rutile-type titanium dioxide and the intensity corresponding to the main peak of Li 2 TiO 3 calculated by multiplying the peak intensity corresponding to the ( ⁇ 133) plane of Li 2 TiO 3 by 100/80 is particularly preferably 5 or less.
• ICDD International Center for Diffraction Data
• PDF is an abbreviation for Powder Diffraction File.
• the lithium titanate powder of the present invention contains at least one metal element selected from Al, W, Ce and Mo on the surfaces of lithium titanate particles constituting the lithium titanate powder. Containing each of the above metal elements means that Al, W, Ce and Mo are detected by a known analysis apparatus such as X-ray fluorescence spectrometry (XRF) and inductively coupled plasma emission spectrometry (ICP-AES) of the lithium titanate powder of the present invention. , respectively.
• XRF X-ray fluorescence spectrometry
• ICP-AES inductively coupled plasma emission spectrometry
• the lower limit of the amount detected by inductively coupled plasma emission spectrometry is usually 0.001% by mass.
• the content of at least one metal element selected from Al, W, Ce and Mo in the lithium titanate powder of the present invention determined by X-ray fluorescence analysis (XRF) in the lithium titanate powder is Al, W, Ce and Mo, the total content is 0.01% by mass or more and 5% by mass or less.
• XRF X-ray fluorescence analysis
• the content of at least one metal element selected from Al, W, Ce and Mo is preferably 0.01% by mass or more and 2% by mass or less, more preferably 0.01% by mass or more and 1.2% by mass or less.
• the content ratio represents the ratio of the mass of the metal element to the mass of the entire lithium titanate powder.
• At least one metal element selected from Al, W, Ce and Mo may be present on the surface of the lithium titanate particles constituting the lithium titanate powder. At least one metal element selected from Al, W, Ce and Mo is preferably contained more on the surface than inside the primary particles of lithium titanate contained in the powder.
• the depth of 1 nm from the surface of the primary particles of the lithium titanate measured by energy dispersive X-ray spectroscopy Let C1 (atm%) be the atomic concentration of the metal element at the depth position, and D2 (atm%) be the atomic concentration of the metal element at a depth of 100 nm from the surface of the lithium titanate particle. It is preferable to satisfy (I), and it is more preferable to satisfy the following formula (II). C1>C2 (I) C1/C2 ⁇ 5 (II)
• the metal element is not detected at a depth of 100 nm from the surface of the primary particles of lithium titanate. It is preferable that the metal element is fixed on the surface of the primary particles in a chemically bonded state. When the metal element exists in such a state, a dense negative electrode layer with few voids can be obtained, and an all-solid secondary battery with excellent initial discharge capacity, initial efficiency and charge rate characteristics can be obtained.
• the lower limit of the detectable amount in measurement by energy dispersive X-ray spectroscopy varies depending on the element to be measured and the state, but is usually 0.5 atm %. Therefore, at a depth of about 100 nm, metal elements may be detected in a range of 0.5 atm % or less.
• the lithium titanate powder of the present invention may contain at least one metal element selected from Al, W, Ce and Mo, and preferably contains at least one metal element selected from Al, Ce and Mo. It is more preferable to contain at least one metal element selected from Al and Mo, and it is even more preferable to contain Al.
• the lithium titanate powder of the present invention which may contain two or more kinds of metal elements, contains at least one or more of these metal elements, thereby improving initial discharge capacity, initial efficiency and charge rate characteristics. can.
• a suitable combination of metal elements includes a combination of Al and Mo, and the ratio of these is Al:Mo (mass ratio), preferably 20:80 to 70:30.
• the D50 of the lithium titanate powder of the present invention is an index of the volume median particle size. It means a particle size at which the cumulative volume frequency calculated from the volume fraction obtained by laser diffraction/scattering particle size distribution measurement is integrated from the smaller particle size to 50%. A measuring method will be described in Examples described later.
• D50 of the primary particles of the lithium titanate powder of the present invention is 0.5 ⁇ m or more, preferably 0.55 ⁇ m or more, from the viewpoint of improving the initial discharge capacity and charge rate characteristics, and the denseness of the negative electrode layer.
• 0.6 ⁇ m or more is more preferable.
• it is 5 ⁇ m or less, preferably 4 ⁇ m or less, more preferably 2.5 ⁇ m or less, further preferably 2 ⁇ m or less, and particularly preferably 1.8 ⁇ m or less.
• the lithium titanate powder may contain primary particles having a primary particle diameter of less than 0.5 ⁇ m and having a cumulative volume frequency of 10% to 50%.
• the cumulative volume frequency of primary particles less than 0.55 ⁇ m may be in the range of 10% to 55%, and the cumulative volume frequency of primary particles less than 0.6 ⁇ m is in the range of 10% to 60%.
• the lithium titanate powder may contain a cumulative volume frequency of primary particles exceeding 5 ⁇ m in a range of 50% to 90%, and a cumulative volume frequency of primary particles exceeding 4.5 ⁇ m in a range of 45% to It may be included in the range of 85%.
• the cumulative volume frequency of primary particles exceeding 4 ⁇ m may be in the range of 40% to 80%, and the cumulative volume frequency of primary particles exceeding 2 ⁇ m may be in the range of 15% to 75%, It may contain a cumulative volume frequency of primary particles greater than 1.8 ⁇ m ranging from 10% to 72%.
• Method for producing lithium titanate powder of the present invention An example of the method for producing the lithium titanate powder of the present invention will be described below by dividing it into a raw material preparation step, a firing step, and a surface treatment step, but the method for producing the lithium titanate powder of the present invention is limited to this. not.
• the raw material of the lithium titanate powder of the present invention consists of a titanium raw material and a lithium raw material. Titanium compounds such as anatase-type titanium dioxide and rutile-type titanium dioxide are used as titanium raw materials. It is preferable that it easily reacts with the lithium raw material in a short time, and from that point of view, anatase type titanium dioxide is preferable. D50 of the titanium raw material is preferably 5 ⁇ m or less in order to sufficiently react the raw material in a short time of sintering.
• Lithium compounds such as lithium hydroxide monohydrate, lithium oxide, lithium hydrogen carbonate, and lithium carbonate are used as lithium raw materials.
• the atomic ratio Li/Ti of Li to Ti should be 0.81 or more, preferably 0.83 or more. This is because if the charge ratio is low, the lithium titanate powder obtained after firing will promote the generation of a specific impurity phase, which may adversely affect the battery characteristics.
• the mixed powder constituting the mixture before firing is measured by a laser diffraction/scattering particle size distribution analyzer.
• D95 is the particle size at which the cumulative volume frequency calculated by volume fraction is 95% when integrated from the smaller particle size.
• the following methods can be used to prepare the mixture.
• the first method is a method in which the raw materials are blended and pulverized at the same time as mixing.
• the second method is a method of pulverizing each raw material until D95 becomes 5 ⁇ m or less and then mixing them or mixing while lightly pulverizing them.
• the third method is a method in which powders composed of fine particles are produced from each raw material by a method such as crystallization, classified as necessary, and mixed or lightly pulverized and mixed.
• the first method in which the raw materials are mixed and pulverized at the same time, is an industrially advantageous method because it requires a small number of steps. Also, a conductive agent may be added at the same time.
• any of the first to third methods there is no particular limitation on the method of mixing raw materials, and either wet mixing or dry mixing may be used.
• a Henschel mixer an ultrasonic dispersing device, a homomixer, a mortar, a ball mill, a centrifugal ball mill, a planetary ball mill, a vibrating ball mill, an attritor high-speed ball mill, a bead mill, a roll mill and the like can be used.
• the mixture obtained by any one of the first to third methods is a mixed powder
• it can be subjected to the next firing step as it is.
• the mixed slurry can be dried by a rotary evaporator or the like and then subjected to the next firing step.
• firing is carried out using a rotary kiln furnace, the mixed slurry can be fed into the furnace as it is.
• the resulting mixture is then fired.
• the maximum temperature during firing is 800°C or higher, preferably 810°C. °C or higher.
• the maximum temperature during firing is 1100°C or less, preferably 1000°C or less, and more preferably 960°C. It is below.
• the holding time at the highest temperature during firing is 2 to 60 minutes, preferably 5 to 45 minutes, more preferably 5 to 35 minutes.
• the residence time at 700° C. to 800° C. is preferably shortened, for example, within 15 minutes.
• the firing method is not particularly limited as long as it can be fired under the above conditions.
• Available firing methods include a fixed bed firing furnace, a roller hearth firing furnace, a mesh belt firing furnace, a fluidized bed firing furnace, and a rotary kiln firing furnace.
• a roller hearth type firing furnace, a mesh belt type firing furnace, and a rotary kiln type firing furnace are preferable.
• the quality of the lithium titanate powder obtained by ensuring the uniformity of the temperature distribution of the mixture during firing is evaluated. For consistency, it is preferable to have a small amount of mixture in the sagger.
• the rotary kiln firing furnace does not require a container to hold the mixture, and can be fired while continuously feeding the mixture, and the heat history of the fired material is uniform, making it possible to obtain homogeneous lithium titanate powder. From this point of view, the firing furnace is particularly preferable for producing the lithium titanate powder of the present invention.
• the atmosphere during firing is not particularly limited regardless of the firing furnace, as long as it is an atmosphere that can remove desorbed moisture and carbon dioxide gas.
• An air atmosphere using compressed air is usually used, but an oxygen, nitrogen, or hydrogen atmosphere may also be used.
• Lithium titanate powder after sintering may be slightly agglomerated, but it does not need to be pulverized to destroy the particles. you should go. If pulverization is not carried out and only pulverization to the extent that agglomeration is broken is carried out, the high crystallinity of the lithium titanate powder after sintering is maintained even after that.
• the lithium titanate powder of the present invention is a lithium titanate powder containing at least one metal element selected from Al, W, Ce and Mo, and is a dense negative electrode when applied as a negative electrode material for an all-solid secondary battery. A layer can be formed and excellent initial discharge capacity, initial efficiency and charge rate characteristics can be imparted.
• the compound containing the metal element hereinafter sometimes referred to as a treating agent
• the lithium titanate powder of the present invention can be produced by a surface treatment step or the like.
• Lithium titanate powder before surface treatment obtained by the above steps (hereinafter sometimes referred to as base material lithium titanate powder. Also, hereinafter, lithium titanate particles constituting the base material lithium titanate powder may be referred to as base material lithium titanate particles) are mixed with a treating agent and preferably heat-treated.
• the compound (treatment agent) containing at least one metal element selected from Al, W, Ce and Mo is not particularly limited when the metal element is Al.
• the metal element includes aluminum oxides, hydroxides, Sulfate compounds, nitrate compounds, fluorides, organic compounds, and metal salt compounds containing aluminum are included.
• Specific examples of Al-containing compounds include aluminum acetate, aluminum fluoride, and aluminum sulfate.
• W it is not particularly limited, but examples include tungsten oxide, tungsten trioxide, tungsten trioxide hydrate, tungsten boride, phosphotungstic acid, tungsten disilicide, tungsten chloride, tungsten sulfide, and tungsten silicon.
• Acid hydrate sodium tungsten oxide, tungsten carbide, tungsten acetate dimer, lithium tungstate, sodium tungstate, potassium tungstate, calcium tungstate, magnesium tungstate, manganese tungstate, ammonium tungstate and the like.
• the metal element is Ce, it is not particularly limited, but examples include cerium oxide, cerium sulfide, cerium hydroxide, cerium fluoride, cerium sulfate, cerium nitrate, cerium carbonate, cerium acetate, cerium oxalate, cerium chloride, and boride. cerium, cerium phosphate, and the like.
• the metal element is Mo
• it is not particularly limited, but examples include molybdenum oxide, molybdenum trioxide, molybdenum trioxide hydrate, molybdenum boride, molybdenum phosphoric acid, molybdenum disilicide, molybdenum chloride, molybdenum sulfide, and molybdenum silicon.
• Acid hydrate sodium molybdenum oxide, molybdenum carbide, molybdenum acetate dimer, lithium molybdate, sodium molybdate, potassium molybdate, calcium molybdate, magnesium molybdate, manganese molybdate, ammonium molybdate, etc.
• aluminum sulfate, its hydrates, aluminum fluoride, lithium tungstate, cerium sulfate and its hydrates, and lithium molybdate are preferred.
• the amount of the compound (treatment agent) containing at least one metal element selected from Al, W, Ce and Mo to be added is within the range of the present invention
• the amount of the metal element in the lithium titanate powder is Although any amount may be used, it may be added at a rate of 0.1% by mass or more relative to the base material lithium titanate powder. Moreover, it may be added at a ratio of 12% by mass or less, preferably 10% by mass or less, and more preferably 8% by mass or less with respect to the lithium titanate powder of the substrate.
• the treatment agent two or more kinds may be used in combination.
• the method of mixing the lithium titanate powder as the base material and the compound containing the metal element is not particularly limited, and either a wet mixing method or a dry mixing method can be employed. It is preferable to uniformly disperse the compound containing the metal element on the surface, and wet mixing is preferable in that respect.
• a paint mixer for example, a paint mixer, a Henschel mixer, an ultrasonic dispersing device, a homomixer, a mortar, a ball mill, a centrifugal ball mill, a planetary ball mill, a vibrating ball mill, an attritor high-speed ball mill, a bead mill, a roll mill, or the like can be used.
• a paint mixer for example, a paint mixer, a Henschel mixer, an ultrasonic dispersing device, a homomixer, a mortar, a ball mill, a centrifugal ball mill, a planetary ball mill, a vibrating ball mill, an attritor high-speed ball mill, a bead mill, a roll mill, or the like can be used.
• a paint mixer for example, a paint mixer, a Henschel mixer, an ultrasonic dispersing device, a homomixer, a mortar, a ball mill, a centrifugal ball mill, a
• the treatment agent and lithium titanate powder as the base material are put into water or an alcohol solvent and mixed in a slurry state.
• the alcohol solvent those having a boiling point of 100° C. or lower, such as methanol, ethanol, and isopropyl alcohol, are preferable because the solvent can be easily removed.
• a water solvent is industrially preferable.
• the amount of the solvent there is no problem as long as the amount of the processing agent and the lithium titanate particles of the substrate are sufficiently wet.
• the amount of the solvent that dissolves the processing agent in the solvent is preferably 50% or more of the total amount of the processing agent added to the solvent. Since the amount of the treating agent dissolved in the solvent increases as the temperature increases, it is preferable to mix the lithium titanate powder of the base material and the treating agent in the solvent while heating. Since the amount of solvent can also be reduced by heating, the method of mixing while heating is an industrially suitable method.
• the temperature during mixing is preferably 40°C to 100°C, more preferably 60°C to 100°C.
• the heat treatment temperature is a temperature at which the metal element diffuses into at least the surface region of the lithium titanate particles of the base material, and the specific surface area is greatly reduced by sintering the lithium titanate particles of the base material. A temperature that does not occur is good.
• the upper limit of the heat treatment temperature may be 700° C. or lower, preferably 600° C. or lower.
• the lower limit of the heat treatment temperature should be 300° C. or higher, preferably 400° C. or higher.
• the heat treatment time may be 0.1 to 8 hours, preferably 0.5 to 5 hours.
• the temperature and time at which the metal element diffuses into at least the surface region of the lithium titanate particles of the base material are preferably set as appropriate, since reactivity varies depending on the compound containing the metal element.
• the heating method in the heat treatment is not particularly limited.
• Usable heat treatment furnaces include a fixed bed furnace, a roller hearth furnace, a mesh belt furnace, a fluidized bed furnace, and a rotary kiln furnace.
• the atmosphere during heat treatment may be either an air atmosphere or an inert atmosphere such as a nitrogen atmosphere.
• the lithium titanate powder after the heat treatment obtained as described above is slightly agglomerated, it does not need to be pulverized so as to destroy the particles. It suffices to perform pulverization and classification to the extent that they are broken.
• the lithium titanate powder of the present invention may be granulated and heat-treated after being mixed with a treating agent in the surface treatment step to obtain a powder containing secondary particles in which primary particles are agglomerated. Any method may be used for granulation as long as secondary particles can be formed, but a spray dryer is preferable because it can process a large amount.
• the dew point may be controlled in the heat treatment process. If the heat-treated powder is exposed to the atmosphere as it is, the amount of moisture contained in the powder increases. Therefore, it is preferable to handle the powder in an environment where the dew point is controlled during cooling in the heat treatment furnace and after the heat treatment. The heat-treated powder may be classified as necessary to bring the particles into the desired maximum particle size range.
• the dew point is controlled in the heat treatment step, it is preferable to seal the lithium titanate powder of the invention in an aluminum laminate bag or the like and then put it in an environment outside the dew point control.
• the heat treatment temperature may be 450° C. or higher and 550° C. or lower. This is because if the heat treatment temperature exceeds 550° C., the specific surface area is greatly reduced, and the battery performance, particularly the charge rate characteristics, is greatly reduced.
• the retention time is preferably 1 hour or more, because it is presumed that if the retention time is short, the water content in the powder will increase and the particle surface state will be affected.
• the periodic table of the present invention refers to the periodic table of long period elements based on the regulations of IUPAC (International Union of Pure and Applied Chemistry).
• An inorganic solid electrolyte is an inorganic solid electrolyte, and a solid electrolyte is a solid electrolyte in which ions can move (an electrolyte that exhibits a solid state at a temperature of 25 ° C.). Since inorganic solid electrolytes are solid in the steady state, they are usually not dissociated or released into cations and anions.
• the inorganic solid electrolyte is not particularly limited as long as it has conductivity of metal ions belonging to Group 1 of the periodic table, and generally has almost no electronic conductivity.
• the inorganic solid electrolyte has the conductivity of metal ions belonging to Group 1 of the periodic table.
• Representative examples of the inorganic solid electrolyte include (A) a sulfide inorganic solid electrolyte and (B) an oxide inorganic solid electrolyte.
• a sulfide solid electrolyte is preferably used because it has high ion conductivity and can form a dense compact with few grain boundaries only by applying pressure at room temperature.
• the sulfide-based inorganic solid electrolyte contains sulfur atoms (S), has conductivity of metal ions belonging to Group 1 of the periodic table, and has electronic insulation. It is preferable to have The sulfide-based inorganic solid electrolyte can be produced by reacting a metal sulfide belonging to Group 1 of the periodic table with at least one sulfide represented by the following general formula (III). ) may be used in combination of two or more.
• MxSy ( III) (M represents any one of P, Si, Ge, B, Al, Ga, and Sb, and x and y represent numbers that give a stoichiometric ratio depending on the type of M.)
• the metal sulfide belonging to Group 1 of the periodic table represents any one of lithium sulfide, sodium sulfide, and potassium sulfide, more preferably lithium sulfide and sodium sulfide, and still more preferably lithium sulfide.
• the sulfide represented by the general formula ( III ) is any one of P2S5 , SiS2 , GeS2 , B2S3 , Al2S3 , Ga2S3 and Sb2S5 is preferred, and P 2 S 5 is particularly preferred.
• composition ratio of each element in the sulfide inorganic solid electrolyte produced as described above is a mixture of the metal sulfide belonging to Group 1 of the periodic table, the sulfide represented by the general formula (III), and elemental sulfur. It can be controlled by adjusting the amount.
• the sulfide inorganic solid electrolyte of the present invention may be amorphous glass, crystallized glass, or a crystalline material.
• Li2SP2S5 Li2SP2S5 - Al2S3 , Li2S - GeS2 , Li2S - Ga2S3 , Li2S - GeS2 - Ga2S3 , Li 2 S—GeS 2 —P 2 S 5 , Li 2 S—GeS 2 —Sb 2 S 5 , Li 2 S—GeS 2 —Al 2 S 3 , Li 2 S—SiS 2 , Li 2 S—Al 2 S 3 , Li 2 S—SiS 2 —Al 2 S 3 , Li 2 S—SiS 2 —P 2 S 5 , Li 10 GeP 2 S 12 .
• LPS glasses and LPS glass-ceramics produced by combining Li 2 SP 2 S 5 are preferred.
• the mixing ratio of the metal sulfide belonging to Group 1 of the periodic table and the sulfide represented by the general formula (III) is not particularly limited as long as it can be used as a solid electrolyte, but 50:50 to 90: A ratio of 10 (molar ratio) is preferred. If the molar ratio of the metal sulfide is 50 or more and 90 or less, the ionic conductivity can be sufficiently increased.
• the mixing ratio (molar ratio) is more preferably 60:40 to 80:20, still more preferably 70:30 to 80:20.
• the sulfide inorganic solid electrolyte includes LiI, LiBr, LiCl, and LiF in addition to metal sulfides belonging to Group 1 of the periodic table and sulfides represented by the general formula (III) in order to increase ion conductivity. It may contain at least one lithium salt such as lithium halide, lithium oxide, lithium phosphate, etc. selected from. However, the mixing ratio of the sulfide inorganic solid electrolyte and these lithium salts is preferably 60:40 to 95:5 (molar ratio), more preferably 80:20 to 95:5.
• Algerodite-type solid electrolytes such as Li 6 PS 5 Cl and Li 6 PS 5 Br are also suitable examples of sulfide inorganic solid electrolytes other than those described above.
• the method for producing the sulfide inorganic solid electrolyte is preferably a solid phase method, a sol-gel method, a mechanical milling method, a solution method, a melt quenching method, etc., but is not particularly limited.
• the oxide-based inorganic solid electrolyte preferably contains oxygen atoms, has metal ion conductivity belonging to Group 1 of the periodic table, and has electronic insulation.
• oxide inorganic solid electrolytes examples include Li3.5Zn0.25GeO4 having a LISICON (lithium superionic conductor) type crystal structure, La0.55Li0.35TiO3 having a perovskite type crystal structure , LiTi 2 P 3 O 12 having a NASICON (Natrium superionic conductor) type crystal structure, Li 7 La 3 Zr 2 O 12 (LLZ) having a garnet type crystal structure, lithium phosphate (Li 3 PO 4 ), lithium phosphate LiPON in which some of the oxygen in the _ _ _ _ _ O 12 and the like are preferably exemplified.
• LISICON lithium superionic conductor
• La0.55Li0.35TiO3 having a perovskite type crystal structure
• LiTi 2 P 3 O 12 having a NASICON (Natrium superionic conductor) type crystal structure
• Li 7 La 3 Zr 2 O 12 (LLZ) having a garnet type crystal structure
• the volume average particle diameter of the inorganic solid electrolyte is not particularly limited, it may be 0.01 ⁇ m or more, preferably 0.1 ⁇ m or more.
• the upper limit may be 100 ⁇ m or less, preferably 50 ⁇ m or less.
• the volume average particle size of the inorganic solid electrolyte can be measured using a laser diffraction/scattering particle size distribution analyzer.
• the content of the inorganic solid electrolyte is not particularly limited, but may be 1% by mass or more, preferably 5% by mass or more, and more preferably 20% by mass or more, in the negative electrode active material composition. , more preferably 30% by mass or more.
• the higher the content of the inorganic solid electrolyte the easier it is to obtain contact between the lithium titanate powder and the solid electrolyte, which is preferable.
• the content of the inorganic solid electrolyte is too large, the battery capacity of the all-solid secondary battery becomes small, so the content should be 70% by mass or less, preferably 50% by mass or less.
• the content of the inorganic solid electrolyte is preferably as small as possible in order to increase the battery capacity of the all-solid secondary battery, but if the content is small, it becomes difficult to make contact between the lithium titanate powder and the solid electrolyte.
• the content ratio of the lithium titanate powder and the inorganic solid electrolyte in the negative electrode active material composition is preferably 99: 1 to 30: 70, more preferably 99: 1 to 30: 70, in terms of the mass ratio of "lithium titanate powder: inorganic solid electrolyte". 95:5 to 40:60, more preferably 80:20 to 50:50, particularly preferably 75:25 to 50:50.
• the negative electrode active material composition of the present invention may contain a conductive agent and a binder in addition to the lithium titanate powder and the inorganic solid electrolyte.
• the conductive agent for the negative electrode is not particularly limited as long as it is an electron conductive material that does not cause chemical changes.
• natural graphite flaky graphite, etc.
• graphites such as artificial graphite
• carbon blacks such as acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black
• single-phase carbon nanotubes multi-wall carbon nanotubes
• Graphite layers are multi-layered concentric cylinders) (non-fishbone), cup-layered carbon nanotubes (fishbone), node-type carbon nanofibers (non-fishbone structure), platelet-type carbon nanofibers ( carbon nanotubes such as card-shaped), and the like.
• Graphites, carbon blacks, and carbon nanotubes may be appropriately mixed and used.
• the specific surface area of carbon blacks is preferably 30 m 2 /g to 3000 m 2 /g, more preferably 50 m 2 /g to 2000 m 2 /g.
• the specific surface area of graphites is preferably 30 m 2 /g to 600 m 2 /g, more preferably 50 m 2 /g to 500 m 2 /g.
• the carbon nanotubes have an aspect ratio of 2-150, preferably 2-100, and more preferably 2-50.
• the amount of the conductive agent added varies depending on the specific surface area of the active material, the type and combination of the conductive agent, and should be optimized.
• the content is preferably 0.5% by mass to 5% by mass. By making it in the range of 0.1% by mass to 10% by mass, the active material ratio is made sufficient, thereby making the initial discharge capacity of the electricity storage device per unit mass and unit volume of the negative electrode layer sufficient. , the conductivity of the negative electrode layer can be further enhanced.
• binder for the negative electrode examples include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyvinylpyrrolidone (PVP), a copolymer of styrene and butadiene (SBR), and a copolymer of acrylonitrile and butadiene. coalesced (NBR), carboxymethyl cellulose (CMC), and the like.
• PTFE polytetrafluoroethylene
• PVDF polyvinylidene fluoride
• PVPVP polyvinylpyrrolidone
• SBR styrene and butadiene
• COC carboxymethyl cellulose
• the molecular weight of polyvinylidene fluoride is 20,000 to 1,000,000. From the viewpoint of further enhancing the binding property of the negative electrode layer, it is preferably 25,000 or more, more preferably 30,000 or more, and even more preferably 50,000 or more.
• the molecular weight is preferably 100,000 or more.
• the amount of the binder added varies depending on the specific surface area of the active material and the type and combination of the conductive agent, and should be optimized. % should be included. From the viewpoint of enhancing the binding property and securing the strength of the negative electrode layer, the content is preferably 0.5% by mass or more, more preferably 1% by mass or more, and even more preferably 2% by mass or more. It is preferably 10% by mass or less, more preferably 5% by mass or less, from the viewpoint of preventing a reduction in the active material ratio and a decrease in the initial discharge capacity of the electricity storage device per unit mass and unit volume of the negative electrode layer.
• the method for producing the negative electrode active material composition of the present invention is not particularly limited. and the like, and a method of adding the lithium titanate powder to a slurry containing a solid electrolyte.
• the negative electrode active material composition of the present invention can provide a dense negative electrode layer with fewer voids than conventional, and excellent initial discharge characteristics, initial efficiency and charge rate characteristics in an all-solid secondary battery is not necessarily clear. not, but can be considered as follows.
• the negative electrode active material composition of the present invention comprises an inorganic solid electrolyte having conductivity of metal ions belonging to Group 1 of the periodic table and at least one metal selected from Al, W, Ce and Mo on the surfaces of lithium titanate particles. and a lithium titanate powder containing the element.
• the lithium titanate particles aggregate together, especially when the particle size of the lithium titanate powder is small, and the lithium titanate powder and the solid electrolyte are mixed in the negative electrode active material composition.
• the presence of metal elements such as Al, W, Ce and Mo on the surface of the lithium titanate particles of the present invention suppresses the aggregation of the lithium titanate particles, and furthermore, the inorganic solid electrolyte, particularly the sulfide solid electrolyte. and is uniformly mixed in the negative electrode active material composition.
• the solid electrolyte and the lithium titanate powder of the present invention form a good solid-solid interface in the negative electrode active material composition, and a dense negative electrode layer with fewer voids than conventional can be formed, resulting in an all-solid secondary battery. It is considered that the characteristics can be improved in Here, in a lithium-ion secondary battery using an organic electrolyte, even if lithium titanate particles aggregate together, such an aggregated portion also contains an organic electrolyte that serves as a carrier for metal ions such as lithium ions. Easily impregnated with liquid. Therefore, since a solid-liquid interface is easily formed, even in such agglomerated portions, metal ions such as lithium ions can be absorbed and released through the organic electrolyte.
• the presence of metal elements such as Al, W, Ce, and Mo on the surface of the lithium titanate particles suppresses the aggregation of the lithium titanate particles, and the inorganic solid electrolyte, particularly Affinity with the sulfide solid electrolyte is enhanced, which makes it possible to obtain a dense negative electrode layer with fewer voids than conventional ones, and effectively solve the problem caused by the occurrence of agglomerated portions as described above. It is.
• the negative electrode active material composition of the present invention can be used for the negative electrode of all-solid secondary batteries.
• the negative electrode active material composition of the present invention is preferably pressure-molded to form a pressure-molded body.
• the conditions for pressure molding are not particularly limited, but the molding temperature may be 15° C. to 200° C., preferably 25° C. to 150° C., and the molding pressure may be 180 MPa to 1080 MPa, preferably 300 MPa to 800 MPa.
• the negative electrode active material composition of the present invention can form a dense molded body with few voids, and therefore can form a dense negative electrode layer with few voids.
• the compact obtained using the negative electrode active material composition of the present invention has a filling rate of 72.5% to 100%, preferably 73.5% to 100%. A method for measuring the filling rate will be described in Examples described later.
• the all - solid secondary battery of the present invention is composed of a positive electrode , a negative electrode, and a solid electrolyte layer positioned between the positive electrode and the negative electrode.
• a negative electrode active material composition containing an inorganic solid electrolyte having conductivity of metal ions belonging to Group 1 of the periodic table is used for the negative electrode layer.
• the method for producing the negative electrode layer is not particularly limited. Suitable examples include a method of applying to an electric body, drying, and press-molding.
• Examples of the negative electrode current collector include aluminum, stainless steel, nickel, copper, titanium, calcined carbon, and those whose surfaces are coated with carbon, nickel, titanium, or silver. Moreover, the surface of these materials may be oxidized, and the surface of the negative electrode current collector may be roughened by surface treatment.
• Examples of the form of the negative electrode current collector include sheet, net, foil, film, punched material, lath, porous material, foam, fiber group, non-woven fabric, and the like.
• Porous aluminum is preferable as the form of the negative electrode current collector. The porosity of the porous aluminum is 80% or more and 95% or less, preferably 85% or more and 90% or less.
• the constituent members such as the positive electrode layer and the solid electrolyte layer can be used without any particular limitation.
• a positive electrode active material used as a positive electrode layer for an all-solid secondary battery a composite metal oxide with lithium containing one or more selected from the group consisting of cobalt, manganese, and nickel is used. be.
• These positive electrode active materials can be used individually by 1 type, or can be used in combination of 2 or more types.
• lithium composite metal oxides examples include LiCoO 2 , LiCo 1-x M x O 2 (where M is Sn, Mg, Fe, Ti, Al, Zr, Cr, V, Ga, Zn, and one or more elements selected from Cu, 0.001 ⁇ x ⁇ 0.05), LiMn 2 O 4 , LiNiO 2 , LiCo 1-x Ni x O 2 (0.01 ⁇ x ⁇ 1), LiCo1 / 3Ni1 / 3Mn1 / 3O2 , LiNi0.5Mn0.3Co0.2O2 , LiNi0.8Mn0.1Co0.1O2 , LiNi0.8Co 0.15 Al 0.05 O 2 , a solid solution of Li 2 MnO 3 and LiMO 2 (M is a transition metal such as Co, Ni, Mn, Fe), and LiNi 1/2 Mn 3/2 O 4
• M is a transition metal such as Co, Ni, Mn, Fe
• LiCoO2 and LiMn2O4 LiCoO2 and LiN
• a lithium-containing olivine-type phosphate can also be used as the positive electrode active material.
• Lithium-containing olivine-type phosphate containing at least one selected from iron, cobalt, nickel and manganese is particularly preferred. Specific examples thereof include LiFePO 4 , LiCoPO 4 , LiNiPO 4 , LiMnPO 4 and the like. Part of these lithium-containing olivine-type phosphates may be replaced with other elements, and part of iron, cobalt, nickel and manganese may be replaced with Co, Mn, Ni, Mg, Al, B, Ti, V and Nb.
• LiFePO4 or LiMnPO4 is preferred.
• the lithium-containing olivine-type phosphate can be used, for example, by being mixed with the positive electrode active material.
• the conductive agent for the positive electrode is an electronically conductive material that does not cause chemical changes.
• examples thereof include graphite such as natural graphite (flaky graphite, etc.), artificial graphite, etc., carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, and the like.
• graphite and carbon black may be appropriately mixed and used.
• the amount of the conductive agent added to the positive electrode active material composition is preferably 1 to 10% by mass, particularly preferably 2 to 5% by mass.
• the positive electrode active material composition contains at least the positive electrode active material and the solid electrolyte, and if necessary, a conductive agent such as acetylene black or carbon black, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), Binders such as styrene/butadiene copolymer (SBR), acrylonitrile/butadiene copolymer (NBR), carboxymethyl cellulose (CMC), ethylene propylene diene terpolymer, and the like may also be included.
• a conductive agent such as acetylene black or carbon black, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), Binders such as styrene/butadiene copolymer (SBR), acrylonitrile/butadiene copolymer (NBR), carboxymethyl cellulose (CMC), ethylene propylene diene terpolymer, and
• the method for producing the positive electrode is not particularly limited, and for example, a method of press forming the powder of the positive electrode active material composition, or a method of adding the powder of the positive electrode active material composition to a solvent to form a slurry, and then forming the positive electrode active material composition.
• a method of press forming the powder of the positive electrode active material composition or a method of adding the powder of the positive electrode active material composition to a solvent to form a slurry, and then forming the positive electrode active material composition.
• Preferable examples include a method of applying the substance to an aluminum foil or a stainless steel lath plate as a current collector, followed by drying and pressure molding.
• the surface of the positive electrode active material may be surface-coated with another metal oxide.
• Surface coating agents include metal oxides containing Ti, Nb, Ta, W, Zr, Al, Si or Li. Specifically , Li4Ti5O12 , Li2Ti2O5 , LiTaO3 , LiNbO3 , LiAlO2 , Li2ZrO3 , Li2WO4 , Li2TiO3 , Li2B4O7 , Li3PO4 , Li2MoO4 , Li3BO3 , LiBO2 , Li2CO3 , Li2SiO3 , SiO2 , TiO2 , ZrO2 , Al2O3 , B2O3 , etc. .
• the solid electrolyte layer is located between the positive electrode and the negative electrode, and although the thickness of the solid electrolyte layer is not particularly limited, it may have a thickness of 1 ⁇ m to 100 ⁇ m.
• the constituent material of the solid electrolyte layer may be the sulfide solid electrolyte or the oxide solid electrolyte, and may be different from the solid electrolyte used for the electrodes.
• the solid electrolyte layer may contain a binder such as butadiene rubber or butyl rubber.
• This raw material mixture slurry is processed into zirconia beads (outer diameter: 0.5 mm) using a bead mill (manufactured by Willie & Bakkofen, model: Dyno Mill KD-20BC, agitator material: polyurethane, vessel inner surface material: zirconia). 65 mm) is filled into the vessel at 80% by volume, and the raw material powder is processed at an agitator peripheral speed of 13 m / s and a slurry feed rate of 55 kg / hr while controlling the vessel internal pressure to be 0.02 to 0.03 MPa. Wet-mixed and pulverized.
• the obtained mixed slurry is introduced into the furnace core tube from the raw material supply side of the firing furnace using a rotary kiln type firing furnace (furnace core tube length: 4 m, furnace core tube diameter: 30 cm, external heating type) equipped with an adhesion prevention mechanism. , dried in a nitrogen atmosphere and calcined.
• the inclination angle of the furnace core tube from the horizontal direction is 2.5 degrees
• the rotation speed of the furnace core tube is 20 rpm
• the flow rate of nitrogen introduced into the furnace core tube from the fired material recovery side is 20 L / min.
• the temperature was set to 600° C. on the raw material supply side, 840° C. on the central portion, and 840° C. on the fired product recovery side, and the time for holding the fired product at 840° C. was 30 minutes.
• the powder passed through the sieve is placed in an alumina sagger, and a mesh belt conveying continuous furnace equipped with a collection box on the outlet side with a temperature of 25 ° C and a dew point controlled at -20 ° C or less, 1 at 500 ° C. heat treated for hours.
• the powder after heat treatment is cooled in the recovery box, classified with a sieve (screen opening: 53 ⁇ m), and the powder that has passed through the sieve is collected in an aluminum laminate bag and sealed, then taken out from the recovery box and lithium titanate. A powder was produced.
• Production Examples 2 to 8, Production Examples 1a to 5a As shown in Table 1, it was produced in the same manner as in Production Example 1.
• Production Examples 4 to 7 and Production Example 5a in addition to aluminum sulfate hexahydrate (Al 2 (SO 4 ) 3.16H 2 O), lithium molybdate (Li 2 MoO 4 ) was used as the treating agent. was used and added at the same timing as aluminum sulfate 16-hydrate (Al 2 (SO 4 ) 3.16H 2 O).
• lithium molybdate (Li 2 MoO 4 ) and lithium tungstate ( Li 2 WO 4 ) was used, and the addition timing was the same as the addition timing of aluminum sulfate hexahydrate (Al 2 (SO 4 ) 3.16H 2 O).
• cerium sulfate tetrahydrate (Ce 2 (SO 4 ) 3.4H 2 O) was used instead of aluminum sulfate 16-hydrate (Al 2 (SO 4 ) 3.16H 2 O). was used at the same timing as the addition of aluminum sulfate 16-hydrate (Al 2 (SO 4 ) 3.16H 2 O).
• X-ray fluorescence analysis Identification of metal elements> Elements contained in the lithium titanate powder of each example and each comparative example were quantitatively analyzed using a fluorescent X-ray induction spectrometer (manufactured by SII Technology Co., Ltd., trade name "SPS5100").
• the specific surface area (m 2 /g) of the lithium titanate powder of each production example was measured using a fully automatic BET specific surface area measuring device (manufactured by Mountec Co., Ltd., trade name “Macsorb HM model-1208”). Nitrogen gas was used. 0.5 g of the measurement sample powder was weighed, placed in a ⁇ 12 standard cell (HM1201-031), degassed at 100° C. under vacuum for 0.5 hours, and then measured by the BET single-point method.
• the D50 of the lithium titanate powder of each production example was calculated from a particle size distribution curve measured using a laser diffraction/scattering particle size distribution analyzer (manufactured by Nikkiso Co., Ltd., Microtrac MT3300EXII). Put 50 mg of sample into a container containing 50 ml of ion-exchanged water as a measurement solvent, shake the container by hand until the powder is evenly dispersed in the measurement solvent by visual inspection, and place the container in the measurement cell. It was measured. The crushing treatment applied ultrasonic waves (30 W, 3 s) with an ultrasonic device in the device.
• the atomic concentration of the metal element at a specific position in the obtained lithium titanate particle flake sample was measured by the energy dispersive X-ray spectroscopy (EDS) method as follows. Using a JEOL JEM-2100F type field emission transmission electron microscope (with Cs correction), while observing the cross section of a thin sample at an accelerating voltage of 120 kV, a JEOL UTW type Si (Li) semiconductor attached to the same microscope Using a detector, on a straight line drawn perpendicularly from the contact point with respect to the tangent of the thin piece sample surface, the position of 1 nm inward from the surface of the sample and 100 nm inward from the surface The atomic concentration of the metal element at the position was measured.
• EDS energy dispersive X-ray spectroscopy
• the beam diameter that is, the analysis area was a circle with a diameter of 0.2 nm.
• the source of the detected amount in this measurement was 0.5 atm %.
• C1 (atm%) is the total element concentration of the metal element at a position 1 nm from the surface of the lithium titanate particle toward the inside, and the metal element at a depth of 100 nm from the surface of the lithium titanate particle. The results are shown in Table 2 with the total element concentration of C2 (atm %).
• the lithium titanate powders produced in Production Examples 2 to 3 and Production Examples 1a to 4a were surface-treated in the same manner as in Production Example 1, and the surface treatment was carried out in the same manner as in Production Example 7.
• the surfaces of the lithium titanate powders produced in Production Examples 4 to 6 and Production Example 5a correspond to the respective treatment agents. It is considered that the amount of the metal element is substantially undetected at a depth of 100 nm from the surface of the lithium titanate particle.
• Example 1 A negative electrode active material composition shown in Table 3 below was prepared in the same manner as in Example 1, except that the lithium titanate powder prepared by the production method shown in Table 1 was used.
• Filling rate (%) (pellet density of negative electrode active material composition/((1- ⁇ )Li 6 PS 5 Cl density (true density) + ⁇ x lithium titanate density (true density)) x 100 Then, using the obtained filling rate values, relative to the pellets of the negative electrode active material compositions of Examples 1 to 7 and Examples 1a to 3a based on the value of Comparative Example 1 being 100%. A density ratio was calculated. Table 3 shows the results.
• This pot was set in a planetary ball mill, and mechanical milling was performed at a rotation speed of 510 rpm for 16 hours to obtain a yellow powdery sulfide solid electrolyte (LPS glass).
• LPS glass yellow powdery sulfide solid electrolyte
• a pellet-shaped solid electrolyte layer was obtained by pressing 80 mg of the obtained LPS glass at a pressure of 360 MPa using a pellet molding machine having a molding part with an area of 0.785 cm 2 .
• the battery was charged to 0.5 V with a current corresponding to 0.4 C, which is the theoretical capacity of lithium titanate, and then discharged to 2 V at a current of 0.05 C to determine the 0.4 C charge capacity.
• the charge rate characteristic (%) was calculated by dividing the 0.4C charge capacity by the initial discharge capacity.
• the initial discharge capacities and charge rate characteristics of Examples 1 to 7 and Examples 1a to 3a were examined relative to each value of Comparative Example 1 as 100%. Table 3 shows the evaluation results.
• the C in 1C represents the current value when charging and discharging.
• 1C refers to the current value that can fully discharge (or fully charge) the theoretical capacity in 1/1 hour
• 0.1C means the current value that can fully discharge (or fully charge) the theoretical capacity in 1/0.1 hour. Point.
• Example 7a Comparative Example 2a
• the negative electrode active material composition of the present invention it is possible to suppress the occurrence of agglomeration of lithium titanate particles, thereby making it possible to make the negative electrode layer more dense. can form a continuous path of ions and electrons, so it exhibits excellent battery characteristics.

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