Zirconia-based material powder

Abstract

A zirconia-based material powder according to the present invention contains 30 mass% or more of zirconium oxide, has a particle diameter D50 in a volume-based particle size distribution of 0.8-5 μm, a particle frequency of less than 3% in a particle size distribution range in which the particle diameter is 0.5 μm or less, and a particle frequency of less than 3% in a particle size distribution range in which the particle diamter is 10 μm or more.

Description

Zirconia-based material powder

[0001] The present invention relates to a zirconia-based material powder.

[0002] In recent years, zirconia-based material powders, which are mainly composed of zirconium oxide, have been attracting attention as additive materials that improve the properties of positive electrode active material powders in lithium-ion secondary batteries.

[0003] A commonly known method of adding Zr is to mechanically mix a zirconia-based material powder with an electrode active material precursor powder and a Li salt. It is considered preferable to use a zirconia-based material powder with a small particle size for this purpose in order to ensure uniform distribution of Zr in the sample.

[0004] Widely known methods for providing zirconia-based material powders with small particle sizes include a method of pulverizing zirconia-based material powders produced by various methods using a dry ball mill and a method of pulverizing using a wet bead mill (e.g., Patent Document 1).

[0005] Patent Document 1 discloses a method for producing a fine zirconia powder, which comprises drying a mixed solution containing a hydrated zirconia sol, the production rate of which is 90% or more obtained by hydrolysis of an aqueous zirconium salt solution, and a yttrium compound, the mixed solution having an yttria content of 2 to 4 mol%, and calcining the dried mixed solution at a temperature of 750 to 1150°C to obtain a zirconia powder, mixing the powder with an aqueous solution to obtain a zirconia slurry having a pH of 7 or less or 9 or more, and wet-pulverizing the slurry (claim 4).

[0006] Japanese Patent Application Laid-Open No. 2000-185919

[0007] However, in the wet milling method described in Patent Document 1, the particle size becomes small to the submicron order due to the strong crushing force. If the particle size of the zirconia-based material powder is too small, the Zr coverage on the surface of the raw powder of the positive electrode active material becomes higher than necessary, which increases the resistance of the electrode active material particles, and there is a concern that the benefits of adding the zirconia-based material powder will not be fully obtained. In addition, powders with particle sizes on the submicron order are susceptible to moisture absorption in the atmosphere, which raises concerns about moisture aggregation between particles and resulting in coarse grains.

[0008] In addition, not only for applications in lithium-ion secondary batteries, but also for other applications, powders with particle sizes that are smaller than necessary and have poor fluidity can cause clogging and sticking in powder transport lines in industrial processes, making them impractical from the standpoint of handling.

[0009] On the other hand, in dry grinding, particles cannot be sufficiently ground, resulting in a state in which fine particles and coarse particles coexist.

[0010] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a zirconia-based material powder that is easy to handle in industrial processes.

[0011] The present inventors have conducted extensive research and have found that the above-mentioned problems can be solved by employing the following configuration, thereby completing the present invention.

[0012] That is, the present invention provides the following: (1) A powder containing zirconium oxide in an amount of 30 mass % or more, and having a particle diameter D in a volumetric particle size distribution ５０ a particle size distribution in which the particle frequency in the particle diameter range of 0.5 μm or less is less than 3%, and a particle size distribution in which the particle frequency in the particle diameter range of 10 μm or more is less than 3%.

[0013] According to the above configuration, the particle diameter D ５０Since the particle size is 0.8 μm or more and 5 μm or less, it can be said that the particle size is appropriately small. Furthermore, according to the above configuration, the particle frequency in the particle size range of 0.5 μm or less in the particle size distribution is less than 3%, and the particle frequency in the particle size range of 10 μm or more in the particle size distribution is less than 3%, so it can be said that the powder does not contain excessively fine particles or coarse particles. Thus, according to the above configuration, the powder has an appropriately small particle size and does not contain excessively fine particles or coarse particles, so it is easy to handle in industrial processes. Therefore, it is preferable as a raw material powder to be used in the production of a composite oxide containing Zr.

[0014] Furthermore, according to the above configuration, the particle size is appropriately small and does not contain excessively fine particles or coarse particles, and therefore the powder can be suitably used as an additive material for improving the properties of the positive electrode active material powder of a lithium ion secondary battery.

[0015] The present invention further provides the following: (2) The zirconia-based material powder according to (1) above, characterized in that, in a pore diameter distribution determined by mercury intrusion porosimetry, the pore volume in the pore diameter range of 10 nm or more and less than 6,000 nm is 0.6 mL / g or less.

[0016] When the pore volume in the pore diameter range of 10 nm or more but less than 6000 nm is 0.6 mL / g or less, the secondary particles have few pores that are easily pulverized and are hard. Therefore, atomization is unlikely to occur when mechanical load is applied in the composite oxide production process or powder transport process. As a result, the powder is more suitable as a raw material powder for use in producing a Zr-containing composite oxide.

[0017] Furthermore, the present invention provides the following: (3) The particle diameter D in the particle size distribution ５０ and the ratio of the average particle diameter in the particle size distribution [(particle diameter D ５０ ) / (average particle diameter)] satisfies the following formula [1]: ５０ ) / (average particle diameter)]≦1.3

[0018] Ratio [(particle size D ５０) / (average particle diameter)] is 1 means that the particle size distribution is symmetrical with respect to the frequency peak. ５０ When the ratio of [(average particle diameter)] / (average particle diameter)] is 0.7 or more and 1.3 or less, the particle size distribution is relatively symmetrical with respect to the frequency peak, and the particles have a more uniform particle diameter. Furthermore, when such a powder is used as an additive material for a positive electrode active material powder for a lithium ion secondary battery, it becomes easy to obtain a positive electrode active material in which Zr is more appropriately coated and solid-solved.

[0019] Furthermore, the present invention provides the following: (4) The zirconia-based material powder according to any one of (1) to (3) above, characterized in that the zirconium oxide content is 90 mass % or more.

[0020] When the content of zirconium oxide is 90 mass % or more, it can be particularly suitably used as an additive material that improves the characteristics of the positive electrode active material powder for lithium ion secondary batteries.

[0021] According to the present invention, it is possible to provide a zirconia-based material powder that is easy to handle in industrial processes.

[0022] 1 is a SEM image of the zirconia-based material powder obtained in Example 1. FIG. 2 is a SEM image of the zirconia-based material powder obtained in Example 2. FIG. 3 is a SEM image of the zirconia-based material powder obtained in Example 4. FIG. 4 is a SEM image of the zirconia-based material powder obtained in Example 6. FIG. 5 is a SEM image of the zirconia-based material powder obtained in Comparative Example 1. FIG. 6 is a SEM image of the zirconia-based material powder obtained in Comparative Example 2. FIG. 7 is a SEM image of the zirconia-based material powder obtained in Comparative Example 4. FIG. 8 is a SEM image of the zirconia-based material powder obtained in Comparative Example 5.

[0023] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

[0024] [Zirconia-based material powder] The zirconia-based material powder according to this embodiment contains 30 mass % or more of zirconium oxide, and has a particle diameter D in a volume-based particle size distribution. ５０is 0.8 μm or more and 5 μm or less, the particle frequency in the particle diameter range of 0.5 μm or less in the particle size distribution is less than 3%, and the particle frequency in the particle diameter range of 10 μm or more in the particle size distribution is less than 3%.

[0025] As described above, the zirconia-based material powder according to this embodiment has a particle diameter D ５０ The particle diameter D (median diameter) is 0.8 μm or more and 5 μm or less. ５０ Since the particle size is 0.8 μm or more and 5 μm or less, it can be said that the particle size is appropriately small.

[0026] The particle diameter D ５０ The particle diameter D is preferably 0.9 μm or more, and more preferably 1 μm or more. ５０ The particle diameter D is preferably 4 μm or less, more preferably 3 μm or less. ５０ is preferably 0.9 μm or more and 4 μm or less, more preferably 1 μm or more and 3 μm or less.

[0027] The particle diameter D ５０ refers to the value obtained by the method described in the Examples.

[0028] The zirconia-based material powder has a particle frequency of less than 3% in the particle size distribution in the range of particle diameters of 0.5 μm or less, and a particle frequency of less than 3% in the range of particle diameters of 10 μm or more. Since the particle frequency of less than 3% in the particle size distribution in the range of particle diameters of 0.5 μm or less can be said to be free of excessively fine particles. Furthermore, since the particle frequency of less than 3% in the range of particle diameters of 10 μm or more can be said to be free of excessively coarse particles.

[0029] The particle frequency in the particle size distribution in the particle diameter range of 0.5 μm or less is preferably 2% or less, more preferably 1% or less. The particle frequency in the particle diameter range of 0.5 μm or less in the particle size distribution is preferably as small as possible, for example, 0.01% or more, 0.05% or more, etc. The particle frequency in the particle diameter range of 0.5 μm or less in the particle size distribution is preferably 0.01% or more and 2% or less, more preferably 0.05% or more and 1% or less.

[0030] The particle frequency in the particle size distribution in the particle diameter range of 10 μm or more is preferably 2% or less, more preferably 1% or less. The particle frequency in the particle diameter range of 10 μm or more in the particle size distribution is preferably as small as possible, for example, 0.01% or more, 0.05% or more, etc. The particle frequency in the particle diameter range of 10 μm or more in the particle size distribution is preferably 0.01% or more and 2% or less, more preferably 0.05% or more and 1% or less.

[0031] The particle frequency in the particle diameter range of 0.5 μm or less in the particle size distribution and the particle frequency in the particle diameter range of 10 μm or more in the particle size distribution refer to values ​​obtained by the method described in the Examples.

[0032] The zirconia-based material powder preferably has a pore volume of 0.6 mL / g or less in the pore diameter range of 10 nm or more and less than 6000 nm in the pore diameter distribution determined by mercury intrusion porosimetry. When the pore volume is 0.6 mL / g or less in the pore diameter range of 10 nm or more and less than 6000 nm, the secondary particles have few pores that are easily pulverized and are hard. Therefore, atomization is less likely to occur when mechanical loads are applied in the composite oxide production process or powder transport process. As a result, the powder is more suitable as a raw material powder for use in producing a Zr-containing composite oxide.

[0033] The pore volume in the pore diameter range of 10 nm or more and less than 6000 nm is more preferably 0.55 mL / g or less, and even more preferably 0.5 mL / g or less. The pore volume in the pore diameter range of 10 nm or more and less than 6000 nm is preferably as small as possible, for example, 0.4 mL / g or more, 0.45 mL / g or more. The pore volume in the pore diameter range of 10 nm or more and less than 6000 nm is more preferably 0.4 mL / g or more and 0.55 mL / g or less, and even more preferably 0.45 mL / g or more and 0.5 mL / g or less.

[0034] The pore volume in the pore diameter range of 10 nm or more and less than 6000 nm refers to a value obtained by the method described in the Examples.

[0035] The zirconia-based material powder has the particle diameter D ５０ and the ratio of the average particle diameter in the particle size distribution [(particle diameter D ５０ ) / (average particle diameter)] preferably satisfies the following formula [1]: 0.7≦[(particle diameter D ５０ ) / (average particle diameter)]≦1.3

[0036] Ratio [(particle size D ５０ ) / (average particle diameter)] is 1 means that the particle size distribution is symmetrical with respect to the frequency peak. ５０ When the ratio of [(average particle diameter)] / (average particle diameter)] is 0.7 or more and 1.3 or less, the particle size distribution is relatively symmetrical with respect to the frequency peak, and the particles have a more uniform particle diameter. Furthermore, when such a powder is used as an additive material for a positive electrode active material powder for a lithium ion secondary battery, it becomes easy to obtain a positive electrode active material in which Zr is more appropriately coated and solid-solved.

[0037] The ratio [(particle diameter D ５０ ) / (average particle diameter)] is more preferably 0.75 or more, and even more preferably 0.85 or more. ５０ The ratio [(particle diameter D ５０ ) / (average particle diameter)] is more preferably 0.75 or more and 1.25 or less, and even more preferably 0.85 or more and 1.15 or less.

[0038] The average particle size is preferably 0.8 μm or more and 6 μm or less. The average particle size is more preferably 1 μm or more, and even more preferably 1.5 μm or more. The average particle size is more preferably 5 μm or less, and even more preferably 4 μm or less. The average particle size is more preferably 1 μm or more and 5 μm or less, and even more preferably 1.5 μm or more and 4 μm or less.

[0039] The average particle size refers to a value obtained by the method described in the Examples.

[0040] The zirconia-based material powder has a particle diameter D１０ It is preferable that the particle diameter D is 0.6 μm or more. １０ When the particle size is 0.6 μm or more, it can be said that the particle size is less likely to contain excessive fine particles.

[0041] The particle diameter D １０ The particle diameter D is more preferably 0.7 μm or more, and further preferably 0.8 μm or more. １０ is the particle diameter D ５０ Smaller than.

[0042] The particle diameter D １０ refers to the value obtained by the method described in the Examples.

[0043] The zirconia-based material powder has a particle diameter D ９０ It is preferable that the particle diameter D is 9 μm or less. ９０ When the particle size is 9 μm or less, it can be said that the particle size is less likely to contain excessively coarse particles.

[0044] The particle diameter D ９０ The particle diameter D is more preferably 8 μm or less, and further preferably 7 μm or less. ９０ is the particle diameter D ５０ Greater than.

[0045] The particle diameter D ９０ refers to the value obtained by the method described in the Examples.

[0046] The zirconia-based material powder contains zirconium oxide, and the content of the zirconium oxide is 30 mass % or more based on the total mass of the zirconia-based material powder.

[0047] The preferred range of the zirconium oxide content varies depending on the application.

[0048] When the zirconia-based material powder is used as an additive material for a positive electrode active material powder of a lithium-ion secondary battery, the content of the zirconium oxide is preferably 50% by mass or more, more preferably 90% by mass or more, based on the total mass of the zirconia-based material powder. Furthermore, when the zirconia-based material powder is used as an additive material for a positive electrode active material powder of a lithium-ion secondary battery, the content of the zirconium oxide may be 100% by mass based on the total mass of the zirconia-based material powder. That is, when the zirconia-based material powder is used as an additive material for a positive electrode active material powder of a lithium-ion secondary battery, the zirconia-based material powder may be composed solely of zirconium oxide. When the zirconium oxide content is 90% by mass or more, the zirconia-based material powder is particularly suitable for use as an additive material for improving the properties of a positive electrode active material powder of a lithium-ion secondary battery.

[0049] When the zirconia-based material powder is used for purposes other than as an additive material for positive electrode active material powders of lithium ion secondary batteries (for example, when used for catalyst purposes, fine ceramic purposes, electronic materials, etc.), the content of the zirconium oxide is preferably 30 mass% or more, and more preferably 40 mass% or more, based on the total amount of the zirconia-based material powder. When the zirconia-based material powder is used for purposes other than as an additive material for positive electrode active material powders of lithium ion secondary batteries, the content of the zirconium oxide is preferably 90 mass% or less, and more preferably 80 mass% or less, based on the total amount of the zirconia-based material powder. When the zirconia-based material powder is used for purposes other than as an additive material for positive electrode active material powders of lithium ion secondary batteries, the content of the zirconium oxide is preferably 30 mass% or more and 90 mass% or less, and more preferably 40 mass% or more and 80 mass% or less, based on the total amount of the zirconia-based material powder. When the zirconia-based material powder is used for purposes other than as an additive material for positive electrode active material powder of a lithium ion secondary battery, by setting the content of the zirconium oxide to 40 mass % or more and 80 mass % or less with respect to the entire zirconia-based material powder, other elements (for example, various transition metals) can be contained, and the zirconia-based material powder can have properties corresponding to the other elements added.

[0050] The zirconia-based material powder may contain one or more elements selected from the group consisting of La, Ce, Nd, Y, Sc, Ti, Fe, Nb, Gd, Pr, Hf, Ta, W, Li, Na, Mg, Ca, Sr, and Ba. Hereinafter, the one or more elements selected from the group consisting of La, Ce, Nd, Y, Sc, Ti, Fe, Nb, Gd, Pr, Hf, Ta, W, Li, Na, Mg, Ca, Sr, and Ba are also referred to as "additional elements." When the zirconia-based material powder contains the additional element, it can exhibit properties corresponding to the added additional element. Therefore, the zirconia-based material powder can be used for various applications other than as an additive material for positive electrode active material powders of lithium-ion secondary batteries. It can also impart additional properties to additive materials for positive electrode active material powders of lithium-ion secondary batteries. The zirconia-based material powder does not necessarily contain the additional element.

[0051] When the zirconia-based material powder contains the additional element, the content of the additional element varies depending on the application, but is preferably 20% by mass or more and 60% by mass or less in terms of oxide, relative to the entire zirconia-based material powder. When the zirconia-based material powder contains the additional element, the content of the additional element is more preferably 10% by mass or more, and even more preferably 20% by mass or more in terms of oxide, relative to the entire zirconia-based material powder. When the zirconia-based material powder contains the additional element, the content of the additional element is more preferably 70% by mass or less, and even more preferably 60% by mass or less in terms of oxide, relative to the entire zirconia-based material powder. When the zirconia-based material powder contains the additional element, the content of the additional element is more preferably 10% by mass or more and 70% by mass or less, and even more preferably 20% by mass or more and 60% by mass or less in terms of oxide, relative to the entire zirconia-based material powder.

[0052] The total content of the zirconium oxide and the additional element varies depending on the application, but is preferably 10% by mass or more and 90% by mass or less in terms of oxides, relative to the entire zirconia-based material powder. The total content of the zirconium oxide and the additional element is more preferably 20% by mass or more, and even more preferably 30% by mass or more, in terms of oxides, relative to the entire zirconia-based material powder. The total content of the zirconium oxide and the additional element is more preferably 80% by mass or less, and even more preferably 70% by mass or less, in terms of oxides, relative to the entire zirconia-based material powder. The total content of the zirconium oxide and the additional element is more preferably 20% by mass or more and 80% by mass or less, and even more preferably 30% by mass or more and 70% by mass or less, in terms of oxides.

[0053] The zirconia-based material powder may contain elements other than the zirconium oxide and the additional elements.

[0054] [Method for Producing Zirconia-Based Material Powder] An example of a method for producing a zirconia-based material powder will be described below, although the method for producing a zirconia-based material powder of the present invention is not limited to the following example.

[0055] The method for producing a zirconia-based material powder according to this embodiment includes: Step 1, in which a dicarboxylic acid species is added to an aqueous zirconium oxychloride solution heated to 30°C or higher and 60°C or lower; Step 2, in which, after Step 1, a sulfuric acid species is added to generate core particles composed of basic zirconium sulfate and basic dicarboxylic acid, and the core particles are allowed to grow; Step 3, in which, after Step 2, a slurry containing the core particles is neutralized to generate zirconium hydroxide; and Step 4, in which, after Step 3, the zirconium hydroxide is heat-treated to obtain a zirconia-based material powder.

[0056] <Step 1> In the method for producing a zirconia-based material powder according to this embodiment, first, a dicarboxylic acid species is added to an aqueous solution of zirconium oxychloride heated to 30°C or higher and 60°C or lower.

[0057] The concentration of the aqueous zirconium oxychloride solution is not particularly limited, but is preferably 1M or more and 2M or less, more preferably 1.2M or more and 1.8M or less, in terms of Zr concentration.

[0058] The heating temperature is more preferably 35° C. or higher, and even more preferably 40° C. or higher. The heating temperature is more preferably 70° C. or lower, and even more preferably 60° C. or lower. The heating temperature is more preferably 35° C. or higher and 70° C. or lower, and even more preferably 40° C. or higher and 60° C. or lower.

[0059] The dicarboxylic acid species may be any dicarboxylic acid having two carboxyl groups in the molecule, and examples thereof include saturated aliphatic dicarboxylic acids such as oxalic acid, malonic acid, and succinic acid; unsaturated aliphatic dicarboxylic acids such as maleic acid and fumaric acid; and aromatic dicarboxylic acids such as phthalic acid and isophthalic acid. Among these, malonic acid is preferred from the viewpoint of water solubility.

[0060] <Step 2> After the step 1, sulfuric acid seeds are added to generate core particles made of basic zirconium sulfate and basic dicarboxylic acid, and the core particles are grown.

[0061] Step 2 can be performed at the same heating temperature as Step 1, or after a new temperature set within a range of 30°C to 60°C. When the dicarboxylic acid species is not added, i.e., when a sulfuric acid species is added to a zirconium oxychloride aqueous solution to produce a basic zirconium sulfate precipitate without adding the dicarboxylic acid species, precipitation occurs only at relatively high temperatures (e.g., 75°C or higher). However, precipitation at such relatively high temperatures proceeds rapidly, further promoting particle growth. As a result, the resulting particles are relatively coarse. On the other hand, in the method for producing a zirconia-based material powder according to this embodiment, the addition of dicarboxylic acid species allows particles to be produced under mild conditions (e.g., 30°C to 60°C). This prevents the particles in the slurry from becoming too coarse. The particle size of the resulting zirconia-based material powder tends to decrease as the heating temperature decreases and increase as the heating temperature increases.

[0062] The amount of the dicarboxylic acid species added is ２ The ratio of the dicarboxylic acid species to the total weight of the polymer is preferably in the range of 0.2 to 0.7. By setting the amount of the dicarboxylic acid species to 0.2 or more, particle formation under milder conditions becomes possible. By setting the amount of the dicarboxylic acid species to 0.7 or less, unintended reactions can be prevented from proceeding.

[0063] The sulfate species is not limited as long as it reacts with zirconium ions to produce a sulfate salt (i.e., a sulfation reagent), and examples thereof include sodium sulfate, potassium sulfate, ammonium sulfate, etc. The sulfate species may be in any form, such as a powder or a solution.

[0064] The sulfate species is sulfate radical (SO ４ ２－ ) / ZrO ２ It is preferable to add them so that the weight ratio is 0.3 or more and 0.7 or less.

[0065] The step 2 may include a step 2-1 of adding a first sulfuric acid species and maintaining the mixture for 30 minutes to 75 minutes to obtain a slurry containing core particles made of basic zirconium sulfate and basic dicarboxylic acid, and a step 2-2 of adding a second sulfuric acid species after the step 2-1 to grow the core particles.

[0066] By dividing the addition of the sulfuric acid species into two stages, such as the above-mentioned step 2-1 and step 2-2, it becomes possible to obtain a zirconia-based material powder having a more appropriately fine particle size.

[0067] The first sulfate species and the second sulfate species may be the same as or different from each other.

[0068] The total amount of the first sulfuric acid species added in the step 2-1 and the second sulfuric acid species added in the step 2 is the sulfate radical (SO ４ ２－ ) / ZrO ２ It is preferable to add the above components so that the weight ratio of these components is 0.2 or more and 0.7 or less.

[0069] The amount of sulfuric acid species added in step 2-1 is preferably 0.5 to 0.9, more preferably 0.6 to 0.8, relative to the total amount of the first sulfuric acid species added in step 2-1 and the second sulfuric acid species added in step 2-2. The smaller the proportion of sulfuric acid species (first sulfuric acid species) added in step 2-1, the slower the generation of core particles, the smaller the particle diameter, and the larger the number of particles. When the second sulfuric acid species is added in step 2-2 under this condition, particle growth proceeds using the particles as core particles, and as a result, particles with a small diameter tend to be obtained.

[0070] The retention time in 2-1 is preferably 30 minutes or more, more preferably 45 minutes or more. The retention time in 2-1 is preferably 90 minutes or less, more preferably 75 minutes or less. The retention time in 2-1 is preferably 30 minutes or more and 75 minutes or less, more preferably 45 minutes or more and 75 minutes or less. By setting the retention time in 2-1 within the above numerical range, a slurry containing core particles can be suitably obtained.

[0071] The holding time in 2-2 is preferably 5 minutes or more, more preferably 10 minutes or more. The holding time in 2-2 is preferably 30 minutes or less, more preferably 20 minutes or less. The holding time in 2-2 is preferably 5 minutes or more and 30 minutes or less, more preferably 10 minutes or more and 20 minutes or less. By setting the holding time in 2-2 within the above numerical range, the core particles can be suitably grown.

[0072] <Step 3> After step 2, the slurry containing the core particles is neutralized with an alkali to produce zirconium hydroxide. The alkali is not limited, and for example, ammonium hydroxide, ammonium bicarbonate, sodium hydroxide, potassium hydroxide, etc. can be used. Among these, sodium hydroxide is preferred from the viewpoint of industrial cost.

[0073] The amount of alkali to be added is not particularly limited as long as it can produce zirconium hydroxide as a precipitate from the slurry (basic zirconium sulfate solution) containing the core particles. Usually, the alkali is added so that the pH of the solution becomes 11 or higher, preferably 12 or higher.

[0074] After the neutralization reaction, the zirconium hydroxide-containing solution is preferably kept at a temperature of 35° C. to 60° C. for 1 hour or longer, which allows the produced precipitate to mature and makes it easier to filter.

[0075] Next, the zirconium hydroxide is recovered by solid-liquid separation, such as filtration, centrifugation, or decantation.

[0076] After the zirconium hydroxide is recovered, it is preferable to wash the zirconium hydroxide with water to remove any adhering impurities.

[0077] The zirconium hydroxide may be dried by natural drying or by heating.

[0078] <Step 4> After step 3, the zirconium hydroxide is heat-treated to obtain a zirconia-based material powder. The heat treatment temperature is not particularly limited, but is preferably about 400 to 900°C for about 5 to 10 hours. The heat treatment atmosphere is preferably air or an oxidizing atmosphere.

[0079] The obtained zirconia-based material powder may be subjected to a treatment to deflocculate the agglomerates, if necessary, for the purpose of improving the handling properties.

[0080] The method for producing a zirconia-based material powder according to this embodiment has been described above.

[0081] The present invention will be described in detail below using examples, but the present invention is not limited to the following examples as long as it does not depart from the gist of the invention.

[0082] The maximum and minimum values ​​of the content of each component shown in the following examples should be considered as the preferred minimum and maximum values ​​of the present invention, regardless of the content of other components. Also, the maximum and minimum values ​​of the measured values ​​shown in the following examples should be considered as the preferred minimum and maximum values ​​of the present invention, regardless of the content (composition) of each component.

[0083] [Preparation of Zirconia-Based Material Powder] Example 1: 8.33 g of malonic acid was added to 100 mL of a zirconium oxychloride aqueous solution (Zr concentration = 1.6 M) heated to 60°C (Step 1). Then, 4.77 g of sodium sulfate powder was added and the mixture was maintained for 60 minutes (Step 2-1). Then, 4.32 g of sodium sulfate powder was added and stirred for 10 minutes to obtain a slurry containing a precipitate containing Zr, sulfuric acid, and malonic acid (Step 2-2). A sodium hydroxide aqueous solution (NaOH concentration = 0.1 M) was added to the obtained slurry to obtain a slurry containing zirconium hydroxide (Step 3). After filtering, the precipitate was washed with distilled water until the Na and Cl contents were less than 100 ppm, yielding a cake of zirconium hydroxide. The recovered zirconium hydroxide cake was heat-treated in a box-type electric furnace at 600°C for 5 hours to obtain the zirconia-based material powder according to Example 1 (Step 4).

[0084] (Example 2) A zirconia-based material powder according to Example 2 was obtained in the same manner as in Example 1, except that the amount of sodium sulfate powder added in step 2-1 was changed to 6.82 g, and the amount of sodium sulfate powder added in step 2-2 was changed to 2.27 g.

[0085] (Example 3) A zirconia-based material powder according to Example 3 was obtained in the same manner as in Example 1, except that the amount of sodium sulfate powder added in step 2-1 was changed to 7.95 g and the amount of sodium sulfate powder added in step 2-2 was changed to 1.14 g.

[0086] Example 4 A zirconia-based material powder according to Example 4 was obtained in the same manner as in Example 1, except that the amount of sodium sulfate powder added in step 2-1 was changed to 9.09 g and step 2-2 was not performed.

[0087] Example 5: 6.82 g of malonic acid was added to 100 mL of an aqueous zirconium oxychloride solution (Zr concentration = 1.6 M) heated to 60°C (Step 1). Then, 6.82 g of sodium sulfate powder was added, and the mixture was maintained for 60 minutes (Step 2-1). Then, 2.27 g of sodium sulfate powder was further added, and the mixture was stirred for 10 minutes, yielding a slurry containing a precipitate containing Zr, sulfuric acid, and malonic acid (Step 2-2). 106.67 mL of an aqueous cerium chloride solution (Ce concentration = 1 M) was added to the resulting slurry. Then, an aqueous sodium hydroxide solution (NaOH concentration = 0.1 M) was further added, yielding a slurry containing zirconium hydroxide (Step 3). After filtering, the precipitate was washed with distilled water until the amounts of Na and Cl contained in the precipitate were less than 100 ppm, yielding a cake consisting of zirconium hydroxide. The recovered zirconium hydroxide cake was heat-treated at 600° C. for 5 hours using a box-type electric furnace to obtain a zirconia-based material powder according to Example 5 (Step 4).

[0088] Example 6 A zirconia-based material powder according to Example 6 was obtained in the same manner as in Example 5, except that the amount of the cerium chloride aqueous solution added was changed to 66.48 mL, and that 1.99 mL of a lanthanum chloride aqueous solution (La concentration = 1 M) and 5.92 mL of a neodymium chloride aqueous solution (Nd concentration = 1 M) were further added at the time of adding the cerium chloride aqueous solution.

[0089] Example 7 A zirconia-based material powder according to Example 7 was obtained in the same manner as in Example 5, except that 11.95 mL of an aqueous yttrium chloride solution (Y concentration=1 M) was added instead of the aqueous cerium chloride solution.

[0090] Example 8 A zirconia-based material powder according to Example 8 was obtained in the same manner as in Example 5, except that 77.69 mL of an aqueous lanthanum chloride solution (La concentration=1 M) was added instead of the aqueous cerium chloride solution.

[0091] Example 9 A zirconia-based material powder according to Example 9 was obtained in the same manner as in Example 5, except that 116.70 mL of an aqueous titanium chloride solution (Ti concentration=1 M) was added instead of the aqueous cerium chloride solution.

[0092] Example 10 A zirconia-based material powder according to Example 10 was obtained in the same manner as in Example 5, except that 89.44 mL of niobium pentachloride (Nb concentration=1 M) was added instead of the aqueous cerium chloride solution.

[0093] Example 11 A zirconia-based material powder according to Example 11 was obtained in the same manner as in Example 1, except that the amount of malonic acid powder added in step 1 was changed to 5.95 g.

[0094] Example 12 A zirconia-based material powder according to Example 12 was obtained in the same manner as in Example 1, except that the amount of malonic acid powder added in step 1 was changed to 11.9 g.

[0095] Comparative Example 1 Ammonia water was added to 100 mL of an aqueous zirconium oxychloride solution (Zr = 1.0 M) until the pH reached 8, thereby obtaining a slurry containing zirconium hydroxide. The resulting slurry was then filtered and washed with distilled water until the amounts of Na and Cl contained in the precipitate were less than 100 ppm, thereby obtaining a cake made of zirconium hydroxide. The recovered zirconium hydroxide cake was heat-treated at 400°C for 5 hours using a box-type electric furnace, thereby obtaining a zirconia-based material powder according to Comparative Example 1.

[0096] (Comparative Example 2) The zirconia-based material powder obtained in Comparative Example 1 was pulverized and mixed for 40 hours in a wet ball mill using water as a dispersion medium. Zirconia beads with a diameter of 5 mm were used for pulverization. The zirconia slurry obtained after pulverization was dried at 110°C, and a zirconia-based material powder according to Comparative Example 2 was obtained.

[0097] Comparative Example 3: 10 L of a 0.37 mol / L aqueous zirconium oxychloride solution was prepared, and a hydrolysis reaction was carried out in a flask equipped with a reflux condenser at boiling temperature for 200 hours. The obtained hydrated zirconia sol was spray-dried and calcined at 960°C for 2 hours. Water and hydrochloric acid were added to the calcined powder to prepare a zirconia slurry with a pH of 4 and a concentration of 55% by mass. The slurry was then pulverized in a vibration mill for 12 hours to obtain a zirconia-based material powder according to Comparative Example 3.

[0098] (Comparative Example 4) 100 mL of an aqueous zirconium oxychloride solution (Zr concentration = 1.6 M) and an aqueous sodium sulfate solution (Na ２ SO ４ 35 mL of aqueous sodium hydroxide solution (NaOH concentration = 1.6 M) was heated to 70 ° C., and 250 mL of aqueous sodium hydroxide solution (NaOH concentration = 2.5 mM) was heated to 90 ° C. Thereafter, the two liquids, the aqueous zirconium oxychloride solution and the aqueous sodium sulfate solution, were mixed by liquid delivery using a metering pump, and the mixed liquid was then delivered directly to an aqueous sodium hydroxide solution heated to 90 ° C. At this time, a tube with an inner diameter of 4 mm, manufactured by Tygon, was used, and a glass Y-shaped tube connector was used at the confluence of the two liquids where the two liquids were mixed and reacted. The delivery rate of the aqueous zirconium oxychloride solution was 10 mL / min, and the flow rate of the aqueous sodium sulfate solution was 3.5 mL / min. The mixture of the aqueous solutions was stirred at 90 ° C. for 30 minutes, and then an aqueous sodium hydroxide solution (NaOH concentration = 0.1 M) was added until the pH reached 11 or higher, thereby obtaining a slurry containing zirconium hydroxide. The precipitate was then filtered and washed with distilled water until the amounts of Na and Cl contained in the precipitate were less than 100 ppm, yielding a cake made of zirconium hydroxide. The recovered zirconium hydroxide cake was heat-treated at 400°C for 5 hours using a box-type electric furnace, yielding a zirconia-based material powder according to Comparative Example 4.

[0099] Comparative Example 5 A zirconia-based material powder according to Comparative Example 5 was obtained in the same manner as in Comparative Example 4, except that the concentration of the aqueous zirconium oxychloride solution was set to Zr concentration=2.2M.

[0100] [Particle diameter D ５０ , particle diameter D １０ , particle diameter D ９０ Measurement of average particle diameter] The particle diameters (particle diameter D ５０ , particle diameter D １０ , particle diameter D ９０, average particle size) were measured using a laser diffraction / scattering particle size distribution analyzer "LA-950" (manufactured by Horiba, Ltd.). More specifically, the dispersions of the zirconia-based material powders of the examples and comparative examples obtained by the dispersion treatment described below were placed in the analyzer (laser diffraction / scattering particle size distribution analyzer "LA-950") and measured. The results are shown in Tables 1 and 2. Tables 1 and 2 show the particle frequency in the particle size range of 0.5 μm or less, the particle frequency in the particle size range of 10 μm or more, and the ratio [(particle diameter D ５０ ) / (average particle size)] is also shown. <Dispersion Treatment> 0.1 g of zirconia-based material powder was added to 40 mL of pure water, and dispersion treatment was carried out for 5 minutes using a tabletop ultrasonic device manufactured by Vervoclear, product name VS-100 III, under the following dispersion conditions. <Dispersion Conditions> Oscillation frequency: 100 kHz High frequency output: 100 W <Measurement Conditions> Refractive index: 2.4 Particle size standard: volume Upper limit of measurement: 3000 μm Lower limit of measurement: 0.01 μm

[0101] [Measurement of pore volume in the pore diameter range of 10 nm or more and less than 6000 nm] For the zirconia-based material powders of the examples and comparative examples, the pore size distribution was obtained by mercury intrusion porosimetry using a pore size distribution measurement device ("Autopore IV9500" manufactured by Micromeritics). The measurement conditions were as follows. <Measurement conditions> Measurement device: pore size distribution measurement device (Autopore IV9500 manufactured by Micromeritics) Measurement range: 0.0036 to 10.3 μm Number of measurement points: 120 Mercury contact angle: 140 degrees Mercury surface tension: 480 dyne / cm

[0102] The pore volume in the pore diameter range of 10 nm or more and less than 6000 nm was calculated using the obtained pore distribution. The results are shown in Tables 1 and 2.

[0103]

[0104]

[0105] [SEM Images] Shape observation was carried out on the zirconia-based material powders of the Examples and Comparative Examples using a scanning electron microscope ("proX PREMIUM" manufactured by Phenom World). Fig. 1 shows an SEM image of the zirconia-based material powder obtained in Example 1, Fig. 2 shows an SEM image of the zirconia-based material powder obtained in Example 2, Fig. 3 shows an SEM image of the zirconia-based material powder obtained in Example 4, Fig. 4 shows an SEM image of the zirconia-based material powder obtained in Example 6, Fig. 5 shows an SEM image of the zirconia-based material powder obtained in Comparative Example 1, Fig. 6 shows an SEM image of the zirconia-based material powder obtained in Comparative Example 2, Fig. 7 shows an SEM image of the zirconia-based material powder obtained in Comparative Example 4, and Fig. 8 shows an SEM image of the zirconia-based material powder obtained in Comparative Example 5.

[0106] As shown in FIGS. 1 to 4, it was confirmed that the zirconia-based material powders of the examples did not contain excessively fine particles or coarse particles, and had relatively uniform particle sizes.

[0107] [Electrode Preparation and Evaluation] 1. Preparation of Positive Electrode 10.17 g of nickel-cobalt manganese hydroxide (manufactured by MTI), 5.07 g of lithium hydroxide monohydrate, and zirconia-based material powder (Examples 1-4, Comparative Examples 1, 2, and 4) were mixed in a mortar and then heat-treated at 750 °C for 5 hours using a box-type electric furnace to obtain lithium nickel-cobalt oxide powder (positive electrode active material powder). 1.8 g of the obtained positive electrode active material powder, 0.1 g of acetylene black, and 0.1 g of polyvinylidene fluoride (Solvay, Solef5130) were added to 2.0 g of NMP (N-methyl-2-pyrrolidone), and mixed using a planetary mixer (Awatori Rentaro, ARE-310LED, manufactured by THINKY Corporation) to obtain a positive electrode slurry. The positive electrode slurry was then applied to aluminum foil using a doctor blade method and then dried. This was pressed and then punched into a disk shape (φ15 mm) to obtain positive electrodes according to Examples 1 to 4, Comparative Examples 1, 2, and 4. In addition, a positive electrode was prepared in the same manner as above except that the zirconia-based material powder was not added, and this was designated as the positive electrode according to Reference Example 1.

[0108] 2. Evaluation <Preparation of coin-shaped half-cell> A coin-shaped lithium-ion secondary battery (standard: CR2032) was prepared using the prepared positive electrode. Li metal foil (φ16 mm) was used as the counter electrode, a mixed solution of ethylene carbonate and diethylene carbonate containing 1 M lithium hexafluorophosphate was used as the electrolyte, and polypropylene was used as the separator.

[0109] <Evaluation of Coin-Type Half Cell> The resulting coin cell was evaluated for charge and discharge using a charge / discharge tester (17216M-10-6, manufactured by Chroma Japan Co., Ltd.). The voltage range was 3.0 to 4.3 V, and the temperature was 20°C. Measurements were taken at a charge C rate of 0.5 C and discharge C rates of 0.1 C and 5 C, and rate characteristics were evaluated by performing five charge / discharge cycles at each discharge C rate. The average value for five charge / discharge cycles was used for evaluation. The ratio of the 5 C discharge capacity to the 0.1 C discharge capacity is shown in Table 3.

[0110] Here, the C-rate represents the discharge rate, and the ratio (%) of the 5C discharge capacity to the 0.1C discharge capacity refers to the amount of electricity discharged at a fast rate (5C) relative to the amount of electricity discharged at a slow rate (0.1C). As can be seen from Table 3, the cells fabricated using positive electrodes containing the zirconia-based material powder of the Examples had a higher ratio of the 5C discharge capacity to the 0.1C discharge capacity compared to the cells fabricated using positive electrodes without the zirconia-based material powder (Reference Example 1) and the cells fabricated using positive electrodes containing the zirconia-based material powder of the Comparative Examples. This indicates that the cells fabricated using positive electrodes containing the zirconia-based material powder of the Examples obtained a larger amount of electricity (improved characteristics) even when discharged at a fast rate. This is thought to be due to the fact that Zr is more uniformly distributed in the positive electrode active material powder of the Examples compared to the positive electrode active material powders of the Reference Example and Comparative Examples.

[0111]

Claims

Contains 30% by mass or more of zirconium oxide, Particle diameter D in volume-based particle size distribution ５０ is 0.8 μm or more and 5 μm or less, the particle frequency in the particle size distribution range of 0.5 μm or less is less than 3%, The zirconia-based material powder is characterized in that the frequency of particles in the particle size distribution range of 10 μm or more is less than 3%.

2. The zirconia-based material powder according to claim 1, wherein in a pore diameter distribution determined by mercury intrusion porosimetry, the pore volume in the pore diameter range of 10 nm or more and less than 6000 nm is 0.6 mL / g or less. 　 The particle diameter D in the particle size distribution ５０ and the ratio of the average particle diameter in the particle size distribution [(particle diameter D ５０ 3. The zirconia-based material powder according to claim 1, wherein the ratio of the average particle diameter to the average particle diameter satisfies the following formula [1]: Equation [1] 0.7≦[(particle diameter D) ５０ [(Average particle diameter)] ≤ 1.3 3. The zirconia-based material powder according to claim 1, wherein the zirconium oxide content is 90 mass % or more.

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