JP2010254563A - Method for producing compound oxide particle and method for producing compound oxide bulk body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing compound oxide particles which can stably mass-produce highly crystalline compound oxide nanoparticles in a short period of time also at a low temperature of ≤500°C. <P>SOLUTION: The method comprises: a mixed liquor preparation process (step S1) where a mixed liquor of two or more kinds of alkoxides and alcohol is prepared; a refluxing process (step S2) where the mixed liquor is made to reflux to prepare a precursor solution containing a composite alkoxide; and a heating process (step S3) where the precursor solution is heated within a closed vessel. The heating process includes a steam introduction process (step S4) where steam is introduced into the closed vessel during the heating, and at least hydrolysis of the composite alkoxide in the precursor solution is progressed to produce compound oxide particles. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a low-temperature synthesis method for highly crystalline composite oxide particles having a nanometer size and a method for producing a composite oxide bulk formed by composite oxide particles having a nanometer size.

Conventionally, for example, Non-Patent Document 1, Patent Documents 1 and 2 have been proposed as methods for producing composite oxide particles such as LiCoO ₂ .

As shown in FIG. 11, the method described in Non-Patent Document 1 is prepared by dissolving LiNO ₃ and Co (NO ₃ ) ₂ .6H ₂ O in water and then mixing an aqueous maleic acid solution as a chelating agent. Nitric acid is gradually added dropwise with stirring to adjust the pH to 1-4. Thereafter, the mixed aqueous solution is slowly heated uniformly at 70 to 80 ° C. to obtain a maleic acid / metal sol, and then the maleic acid / metal sol is further gradually heated to obtain a precursor gel. This precursor gel is heat-treated at 400 ° C. or higher for 1 hour or longer in an air atmosphere to produce a precursor powder, and this precursor powder is calcined at 500 to 700 ° C. for 1 hour or longer in an air atmosphere. LiCoO ₂ powder having a diameter of 30 nm is obtained.

In the method described in Patent Document 1, as shown in FIG. 12, after lithium acetate and cobalt nitrate are dissolved in distilled water, polyacrylic acid (PAA) is mixed as a chelating agent, and the mixed aqueous solution is stirred with nitric acid. Is gradually added dropwise to adjust the pH to 1-4. Thereafter, the mixed aqueous solution is slowly heated uniformly at 50 to 90 ° C. to form a PAA / metal sol, and then the PAA / metal sol is further heated gradually to obtain a gel precursor. This gel precursor is heat-treated at 300 ° C. or higher for 1 hour or longer in an air atmosphere to produce a precursor powder, and this precursor powder is calcined at 400 to 900 ° C. for 1 hour or longer in an air atmosphere. LiCoO ₂ powder having a diameter of 30 nm is obtained.

In the method described in Patent Document 2, as shown in FIG. 13, tetraisopropoxytitanium Ti [OCH (CH ₃ ) ₂ ] ₄ and diethoxybarium Ba (OC ₂ H ₅ ) ₂ as raw material alkoxide are mixed with methanol and 2 -A precursor is prepared by dissolving in a mixed solvent with methoxyethanol, and the precursor is gradually hydrolyzed with water vapor while stirring at room temperature, and then left to stand for several days to obtain a gel (wet gel: particle size 2 nm). ) Is generated. Then, a gel molded object (dry gel) is produced | generated by leaving still at 25 degreeC for 5 days. The dried gel molded body is fired at 1000 ° C. to obtain a barium titanate sintered body having an average particle size of about 0.1 μm.

JP-A-9-175825 JP-A-8-239216

In-Hwan Oh et al. "Low-temperature preparation of ultrafine LiCoO2 powders by the sol-gel method": Journal of Materials Science, Volume 32, Number 12/1997, p. 3177-3182

However, in the methods described in Non-Patent Document 1 and Patent Document 1, in order to obtain LiCoO ₂ particles having an average particle size of 30 nm, a chelating agent and an acid / base catalyst are necessary. A separate process for evaporation is required. This causes problems that the manufacturing process is complicated, the processing time is lengthened, and the manufacturing cost is increased. In the methods described in Non-Patent Document 1 and Patent Document 1, only complex oxide particles having an average particle diameter of about 30 to 100 nm can be obtained, and complex oxide particles having a smaller average particle diameter cannot be obtained.

In the method described in Patent Document 2, it is necessary to finally obtain a sintered body through a sintering process at 1000 ° C. In other words, a gel having a particle size of about 2 nm can be obtained through a step of obtaining a wet gel by introducing steam, but in order to remove residual organic substances, a sintering process at 1000 ° C. is finally performed. After that, it is necessary to obtain a sintered body. Therefore, composite oxide particles having an average particle size of nanometer level cannot be obtained. In Patent Document 2, a mixed solvent having high solubility in the raw material alkoxide is prepared, and the raw material alkoxide is mixed with the mixed solvent. This method is suitable for stable oxide synthesis, but there is a problem that the selection of the raw material alkoxide is limited and various composite oxide particles cannot be produced. Further, the method described in Patent Document 2 requires 5 days just to obtain a gel molded body from a wet gel, and there is a problem that the processing time is prolonged.
That is, in the conventional general sol-gel method including Patent Document 2, since the reaction temperature is too low, the elimination reaction of the alkoxyl group that prevents crystallization due to steric hindrance does not proceed, and an amorphous body is synthesized. Therefore, in order to obtain a high crystallinity, it is considered that heat treatment for reaction and crystallization is finally required.

  The present invention has been made in consideration of such problems, and can stably produce a large amount of highly crystalline composite oxide nanoparticles in a short time and at a low temperature of 500 ° C. or less. It aims at providing the manufacturing method of composite oxide particle which can be performed.

  Another object of the present invention is to provide a composite oxide bulk body that can be easily produced by only high-pressure pressing at room temperature without using a sintering process at high temperature. It is to provide a manufacturing method.

[1] A method for producing composite oxide particles according to the first aspect of the present invention includes a refluxing step of refluxing a mixed solution of a plurality of alkoxides and an alcohol to prepare a precursor solution containing the composite alkoxide, and the precursor. A heating step of heating the body solution in a sealed container, wherein the heating step introduces water vapor into the heated sealed container to advance at least hydrolysis of the composite alkoxide in the precursor solution. And having a water vapor introduction step of generating composite oxide particles.

  Thereby, complex oxide particles can be produced stably and in large quantities in a short time and at a low temperature of 500 ° C. or lower. That is, in the general sol-gel method, as described above, in order to obtain a high crystallinity, it is considered that heat treatment for reaction / crystallization is finally required. It is considered that fine particles with high crystallinity can be formed because alcohol elimination, which is a product of the hydrolysis reaction, easily occurs at a low temperature.

[2] In the first aspect of the present invention, in the steam introduction step, production of a composite solid alkoxide by hydrolysis of the composite alkoxide, dehydration condensation of the composite solid alkoxide, evaporation of the solvent, and crystallization are performed. To do.

[3] In the first aspect of the present invention, the refluxing step is characterized in that the mixed solution is refluxed for a time during which the reaction sufficiently proceeds at the boiling point of the alcohol.

[4] In the first aspect of the present invention, the heating step includes a step of heating the precursor solution in the sealed container at a temperature not lower than the boiling point of the alcohol and not higher than 500 ° C., and drying and solidifying the precursor solution. It is characterized by having.

[5] In the first aspect of the present invention, the heating step heats the precursor solution to a boiling point temperature of the alcohol with an inert gas introduced into the sealed container prior to the water vapor introduction step. Thus, the precursor solution is dried and solidified, and the heating temperature of the precursor solution is increased from the boiling point temperature of the alcohol to 500 ° C. at the maximum with the start of the water vapor introduction step. In this case, the temperature may be raised stepwise, or the temperature rise per unit time may be increased to raise the maximum temperature in a short time.

[6] In the first aspect of the present invention, the water vapor introducing step is characterized in that the oxygen gas that has passed through the humidifier is held for 3 to 5 hours while being introduced into the sealed container.

[7] In the first aspect of the present invention, a cooling step is provided after the water vapor introduction step, and the cooling step stops introduction of the water vapor into the sealed container and introduces oxygen gas not containing water vapor. The temperature is lowered to room temperature.

[8] In the first aspect of the present invention, the manufactured composite oxide particles have an average particle size of 30 nm or less.

[9] Next, the method for producing a complex oxide bulk body according to the second aspect of the invention includes the complex oxide particles produced by the method for producing the complex oxide particles according to the first aspect of the invention described above. It comprises a step of preparing a powder and a pressing step of putting the powder into a mold and pressing it at room temperature to form a composite oxide bulk body.

  Thereby, a complex oxide bulk body can be easily manufactured by only high-pressure pressing at room temperature without using a sintering process at a high temperature.

  As described above, according to the method for producing composite oxide particles according to the present invention, high crystalline composite oxide nanoparticles can be stably and massively produced in a short time and at a low temperature of 500 ° C. or less. Can be produced. It is also possible to produce composite oxide particles containing three or more elements.

  In addition, the method for producing a complex oxide bulk body according to the present invention can easily produce a complex oxide bulk body only by high-pressure pressing at room temperature without using a high-temperature sintering process. .

It is a process block diagram which shows the manufacturing method of the composite oxide particle which concerns on this Embodiment. It is a process block diagram which shows the preferable aspect of the manufacturing method of the composite oxide particle which concerns on this Embodiment. 3A to 3D are process diagrams showing a method for producing a complex oxide bulk body according to the present embodiment. 2 is a process block diagram illustrating a method for producing composite oxide particles according to Example 1. FIG. 2 is a transmission electron micrograph of composite oxide particles according to Example 1. FIG. 6 is a process block diagram illustrating a method for producing composite oxide particles according to Example 2. FIG. 6 is a process block diagram illustrating a method for producing complex oxide particles according to Example 3. FIG. 4 is a transmission electron micrograph of composite oxide particles according to Example 3. 6 is a process block diagram illustrating a method for producing composite oxide particles according to Example 4. FIG. 4 is a transmission electron micrograph of composite oxide particles according to Example 4. It is a process block diagram which shows the manufacturing method of the composite oxide particle of patent document 1. It is a process block diagram which shows the manufacturing method of the composite oxide particle of patent document 2. It is a process block diagram which shows the manufacturing method of the composite oxide particle of patent document 3.

  Embodiments of a method for producing complex oxide particles and a method for producing a product of a complex oxide bulk body according to the present invention will be described below with reference to FIGS.

  As shown in FIG. 1, in the method for producing composite oxide particles according to the present embodiment, a mixed liquid preparation step (step S1) for preparing a mixed liquid of a plurality of types of alkoxide and alcohol, and refluxing the mixed liquid are performed. Then, a reflux process for preparing a precursor solution containing a composite alkoxide (step S2), a heating process for heating the precursor solution in a sealed container (step S3), and water vapor is introduced into the sealed container being heated. And a water vapor introduction step (step S4) in which at least hydrolysis of the composite alkoxide in the precursor solution proceeds to generate composite oxide particles.

  In the refluxing step, the mixed solution is preferably refluxed in the vicinity of the boiling point of the alcohol contained in the mixed solution. Thereby, a plurality of types of alkoxides are substituted with a common alkyl group, and a composite alkoxide having a plurality of elements is generated. Examples of the vicinity of the boiling point of the alcohol include a range of (boiling point−5 °) to (boiling point + 5 °). The reflux time varies depending on the type of alkoxide and alcohol solvent, and may be 1 hour or less, 1 hour or more and 2 hours or less, or 2 hours or more. That is, in this refluxing step, two kinds of reactions, that is, a reaction between alkoxides and a reaction between alkoxides and alcohols are performed. The refluxing time is a time during which these two kinds of reactions are sufficiently performed. I just need it.

  In the heating step, the precursor solution in the sealed container is heated at a temperature not lower than the boiling point of the alcohol and not higher than 500 ° C., and dried and solidified. Thereby, the precursor solution after reflux is dried and solidified to obtain a dried composite alkoxide.

  After the heat treatment for the purpose of drying and solidifying during the heating step, the water vapor introducing step is started, and water vapor is introduced into the airtight container being heated. As a result, hydrolysis / dehydration condensation of the composite solid alkoxide, evaporation of the solvent, and crystallization proceed. In particular, unlike the conventional case, since water vapor is introduced, hydrolysis of the composite alkoxide and dehydration condensation of the composite solid alkoxide proceed slowly. Therefore, at the stage where this water vapor introduction step is completed, a complex oxide powder containing a large amount of highly crystalline complex oxide particles having an average particle size of 30 nm or less is produced. That is, fine particles having high crystallinity can be obtained by subjecting the dried composite alkoxide to hydrolysis / dehydration condensation reaction. This is because the compound alkoxide is dried and solidified and subjected to hydrolysis / dehydration condensation reaction at a high temperature, so that the alkoxyl group that easily causes hydrolysis reaction is easily removed, resulting in steric hindrance. Therefore, it is considered that crystallization has progressed. In addition, since it is difficult for material diffusion to occur in the dry state, it is considered that the reaction of alkoxide is suppressed and grain growth is difficult to occur.

  Here, a preferred embodiment will be described with reference to FIG.

  That is, as shown in FIG. 2, in the heating process (step S3), an inert gas (for example, argon gas) is introduced into the sealed container as shown in step S3a prior to the water vapor introducing process. By removing the air inside and inside the tube and heating the precursor solution to near the boiling point temperature of the alcohol in that state, the solvent is removed and solidified without changing the valence of the metal element in the alkoxide, and steam is introduced. Along with the start of the step (step S4), the heating temperature of the precursor solution is increased from the boiling point temperature of the alcohol to 500 ° C. at the maximum. In this case, the temperature may be raised stepwise, or the temperature rise per unit time may be increased to raise the maximum temperature in a short time. Thereby, crystallization of the composite oxide particles at a low temperature of 500 ° C. or lower is possible.

  In the water vapor introducing step (step S4), it is preferable to hold the oxygen gas that has passed through the humidifier for 3 to 5 hours while introducing the oxygen gas into the sealed container. This facilitates the introduction of water vapor into the sealed container and the generation of oxides.

  It is preferable to set a cooling step (step S5) after the water vapor introduction step (step S4). In this cooling step, the introduction of water vapor into the sealed container is stopped, and the temperature is lowered to room temperature while introducing oxygen gas not containing water vapor. Thereby, the composite oxide can be completely oxidized. In this case, since oxygen gas may be introduced without passing through the humidifier, there is an advantage that the transition from the water vapor introduction process to the cooling process becomes smooth. This leads to a reduction in the time of the entire process.

  Thus, in the method for producing composite oxide particles according to the present embodiment, highly crystalline composite oxide nanoparticles can be produced stably and in large quantities in a short time and at a low temperature of 500 ° C. or less. can do.

  Next, a method for producing a complex oxide bulk body according to the present embodiment will be described with reference to FIGS. 3A to 3D. This manufacturing method is performed at room temperature.

  First, as shown in FIG. 3A, a powder 10 containing composite oxide particles manufactured by the method for manufacturing composite oxide particles according to the above-described embodiment is prepared.

  Thereafter, as shown in FIG. 3B, the powder 10 is put into a sample cube (pressure medium) 12 and sealed with a lid 14.

  Thereafter, as shown in FIG. 3C, all six surfaces of the sample cube are simultaneously pressurized using a cubic anvil type high pressure generator. As a result, as shown in FIG. 3D, a complex oxide bulk body 16 press-molded into a desired shape is obtained.

  As described above, in the method for manufacturing the composite oxide bulk body 16 according to the present embodiment, the composite oxide bulk body can be easily obtained only by high-pressure pressing at room temperature without using a sintering process at a high temperature. 16 can be manufactured.

[Example 1]
Next, Example 1 for producing a powder of LiCoO ₂ composite oxide particles based on the production method of FIG. 2 will be described with reference to FIGS.

First, in the mixed solution preparation step (step S1), a mixed solution of two kinds of metal alkoxides (first metal alkoxide and second metal alkoxide) and alcohol was prepared. Li (OnBu) was used as the first metal alkoxide, and Co (OiPr) ₂ was used as the second metal alkoxide. Here, Bu = C ₄ H ₉ is shown, and Pr = C ₃ H ₇ is shown. Moreover, 2-methoxyethanol (2-methoxyethanol) was used as alcohol.

  In the mixed solution preparation step, the first metal alkoxide, the second metal alkoxide, and the alcohol were mixed using an Erlenmeyer flask in a glove box in a nitrogen atmosphere. The reason for mixing in a nitrogen atmosphere is to suppress the reaction between each metal alkoxide and atmospheric moisture. In addition, the molar ratio of each sample is 1st metal alkoxide = 1 mol, 2nd metal alkoxide = 1 mol, and alcohol = 18.6 mol.

  Thereafter, in the refluxing step (step S2), the above-mentioned mixed solution was refluxed to prepare a precursor solution containing a composite alkoxide. The mouth of the Erlenmeyer flask containing the mixture was sealed, removed from the glove box, and placed in a reflux apparatus. This reflux was performed for 1 hour at the boiling point (125 ° C.) of 2-methoxyethanol, which is an alcohol. This prepared a precursor solution containing 1 mole of LiCoOR (complex alkoxide) per liter.

  Thereafter, a 50 ml beaker containing the precursor solution was placed in a stainless steel reaction vessel, and the reaction vessel was sealed. Of course, the gas inlet and the outlet are opened and closed according to a predetermined sequence.

  In the subsequent heating step, prior to the water vapor introduction step, Ar (argon) gas (Ar gas not containing water vapor: dry Ar gas) is introduced into the reaction vessel, as shown in Step S3a. The precursor solution was heated with the temperature set at the boiling point of alcohol (125 ° C.). The amount of dry Ar gas introduced is 100 cc per minute.

At the stage where the alcohol solvent in the precursor solution has evaporated and solidified, the water vapor introduction step S4 is started, and while introducing oxygen gas (humidified oxygen gas) that has passed through the humidifier into the reaction vessel, The alcohol was gradually raised from the boiling point of the alcohol to a maximum of 350 ° C. First, 125 ° C was held for 1 hour, then 200 ° C was held for 1 hour, and finally 350 ° C was held for 2 hours. As the humidifier, a humidifier having a saturated water vapor pressure P _H2O at 60 to 80 ° C. of P _H2O > 0.2 atm was used.

  Thereafter, in the cooling step (step S5), introduction of the humidified oxygen gas was stopped, and oxygen gas (dry oxygen gas) that did not pass through the humidifier was introduced into the reaction vessel. At this time, the temperature in the reaction vessel was slowly lowered to room temperature over 2 hours. The amount of dry oxygen gas introduced is 100 cc per minute.

  When the cooling process was completed, it was confirmed that a complex oxide powder containing a large amount of complex oxide particles was completed in a 50 ml beaker.

  Thereafter, the powder was put in an agate mortar and pulverized in order to make the particle size of each composite oxide particle of the composite oxide powder substantially uniform. As a result, an ultrafine powder 10 having an average particle size of 30 nm or less was obtained. The average particle size of the composite oxide particles was measured using a transmission electron microscope (see FIG. 5).

  Then, as shown in FIG. 3, the produced powder 10 is put into a sample cube 12, and the powder 10 is press-molded at a press pressure of 4000 MPa, so that a cylindrical composite oxide having a diameter of 5 mm and a height of 8 mm is obtained. Bulk body 16 was produced. It was found that the apparent density of the composite oxide bulk body 16 has a dense structure of about 80% or more of the theoretical value.

[Example 2]
Next, Example 2 for producing a powder of LiCoO ₂ composite oxide particles will be described with reference to FIG.

  The method according to Example 2 performs substantially the same processing as in Example 1 described above, but the raw material charge amount is different, and as a post-process (Step S6), a water washing process (Step S6a) and a heating process ( The difference is that step S6b) is added.

That is, the molar ratio of each sample in the mixed liquid preparation step in step S1 is as follows: 1 mol of the first metal alkoxide (Li (OnBu)), 1 mol of the second metal alkoxide (Co (OiPr) ₂ ), alcohol = 18 .6 mol as compared with Example 1 was used as a composition containing excessive Li. This is because, in order to obtain a constant ratio of LiCoO ₂ (Li: Co = 1: 1), the amount of Li added was increased during preparation of the mixed solution. However, when Li is excessive, LiOH and Li ₂ CO ₃ that cause deterioration of battery characteristics are generated as impurities, and thus a cleaning process and a heat treatment process are newly required. Therefore, in this Example 2, the water washing process (step S6a) and the heating process (step S6b) were added as a post process (step S6).

  In the water washing step of Step S6a, the powder obtained through Steps S1 to S5 in FIG. 6 was stirred and washed using a magnetic stirrer in a beaker containing distilled water. This cleaning is a cleaning for removing the above-described impurities caused by excessive addition of Li.

Then, in the heating process of step S6b, the temperature was maintained at 200 ° C. for 5 to 10 hours for heating. As a result, an ultrafine powder 10 having an average particle size of 15 nm or less was obtained.
Then, as shown in FIG. 3, the produced powder 10 is put into a sample cube 12, and the powder 10 is press-molded at a press pressure of 4000 MPa, so that a cylindrical composite oxide having a diameter of 5 mm and a height of 8 mm is obtained. Bulk body 16 was produced. It was found that the apparent density of the composite oxide bulk body 16 has a dense structure of about 80% or more of the theoretical value.

[Example 3]
Next, Example 3 for producing a powder of LiCoO ₂ composite oxide particles will be described with reference to FIGS.

  The method according to Example 3 performs substantially the same process as in Example 1 described above, but the processes of the heating process (Step S3) and the cooling process (Step S5) after the reflux process (Step S2) are different. The difference is that a heating step (step S6b) is added as a post-step (step S6).

  That is, in the heating step (step S3) after the reflux step, Ar (argon) gas (Ar gas not containing water vapor: dry) is contained in the reaction vessel as shown in step S3a prior to the water vapor introduction step (step S4). The precursor solution was heated with Ar gas introduced. In this heat treatment, the temperature in the reaction vessel was 120 ° C., and the temperature holding time was 1 hour. The amount of dry Ar gas introduced is 100 cc per minute. As a result, the alcohol solvent in the precursor solution is evaporated and solidified.

  In the subsequent steam introduction step (step S4), while maintaining the temperature of 120 ° C., Ar gas, oxygen gas (humidified oxygen gas) that has passed through the humidifier (humidifier similar to Example 1), and the reaction vessel are introduced. Then, the temperature was raised to 150 ° C., and similarly Ar gas and humidified oxygen gas were introduced for 1 hour.

  In step S3b after the steam introduction step, oxygen gas (dry oxygen gas) that does not pass through the humidifier was introduced for 5 to 10 hours while maintaining the temperature at 150 ° C.

  Thereafter, in the cooling step (step S5), the temperature in the reaction vessel was slowly lowered to room temperature over 1 hour while continuing to introduce the dry oxygen gas. The amount of dry oxygen gas introduced is 100 cc per minute.

  When the cooling step (step S5) was completed, it was confirmed that a complex oxide powder containing a large amount of complex oxide particles was completed in a 50 ml beaker.

  In the heating step (step S6b), which is a post-process, the powder was heated with the dry gas introduced into the reaction vessel. In this heat treatment, the temperature in the reaction vessel was 400 ° C., and the temperature holding time was 5 hours. The amount of dry oxygen gas introduced is 100 cc per minute. The reason why the powder is heated to 400 ° C. in this heating step is to remove residual organic substances and completely oxidize them to increase the crystallinity of the composite oxide. Thereafter, the powder was put in an agate mortar and pulverized in order to make the particle size of each composite oxide particle of the composite oxide powder substantially uniform. As a result, an ultrafine powder 10 having an average particle size of 20 nm or less was obtained. The average particle size of the composite oxide particles was measured using a transmission electron microscope (see FIG. 8).

  Then, as shown in FIG. 3, the produced powder 10 is put into a sample cube 12, and the powder 10 is press-molded at a press pressure of 4000 MPa, so that a cylindrical composite oxide having a diameter of 5 mm and a height of 8 mm is obtained. Bulk body 16 was produced. It was found that the apparent density of the composite oxide bulk body 16 has a dense structure of about 80% or more of the theoretical value.

[Example 4]
Next, the composite oxide particles different from the _{LiCoO 2 (Li 7 La 3 Zr} 2 O 12: LLZ) Example 4 to produce a powder will be described with reference to FIGS.
First, in the mixed solution preparation step (step S1), a mixed solution of three kinds of metal alkoxides (first metal alkoxide, second metal alkoxide and third metal alkoxide) and alcohol was prepared. Li (OnBu) was used as the first metal alkoxide, La (OiPr) ₃ was used as the second metal alkoxide, and Zr (OnBu) ₄ was used as the third metal alkoxide. Here, Bu = C ₄ H ₉ is shown, and Pr = C ₃ H ₇ is shown. Moreover, 2-methoxyethanol (2-methoxyethanol) was used as alcohol.

  In this mixed liquid preparation step, as in Example 1, the above-described first metal alkoxide, second metal alkoxide, and third alkoxide were mixed with alcohol in a glove box in a nitrogen atmosphere using an Erlenmeyer flask. In addition, the molar ratio of each sample is 1st metal alkoxide = 7 mol, 2nd metal alkoxide = 3 mol, 3rd metal alkoxide = 2 mol, alcohol = 20 mol.

  Thereafter, in the refluxing step (step S2), the above-mentioned mixed solution was refluxed to prepare a precursor solution containing a composite alkoxide. The mouth of the Erlenmeyer flask containing the mixture was sealed, removed from the glove box, and placed in a reflux apparatus. This reflux was performed for 1 hour at the boiling point (125 ° C.) of 2-methoxyethanol, which is an alcohol. This prepared a precursor solution containing 1 mole of LiLaZrOR (complex alkoxide) per liter.

  Thereafter, a 50 ml beaker containing the precursor solution was placed in a stainless steel reaction vessel, and the reaction vessel was sealed. Of course, the gas inlet and the outlet are opened and closed according to a predetermined sequence.

  In the next heating step (Step S3), prior to the water vapor introduction step (Step S4), as shown in Step S3a, the precursor solution was heated with dry Ar gas introduced into the reaction vessel. In this heat treatment, the temperature in the reaction vessel was 120 ° C., and the temperature holding time was 1 hour. The amount of dry Ar gas introduced is 100 cc per minute. As a result, the alcohol solvent in the precursor solution is evaporated and solidified.

  In the subsequent steam introduction step (step S4), the temperature in the reaction vessel was raised stepwise from the boiling point of the alcohol to 350 ° C. at maximum while introducing Ar gas and water vapor into the reaction vessel. First, 120 ° C. was held for 2 hours, and then 350 ° C. was held for 2 hours.

  Thereafter, in the cooling step (step S5), dry oxygen gas was introduced into the reaction vessel. At this time, the temperature in the reaction vessel was lowered to room temperature over 1 hour. The amount of dry oxygen gas introduced is 100 cc per minute.

  When the cooling process was completed, it was confirmed that a complex oxide powder containing a large amount of complex oxide particles was completed in a 50 ml beaker.

  Thereafter, in the subsequent molding step (step S6c), the produced powder 10 (in this case, LLZ powder) is press-molded by a normal uniaxial pressing method (normal temperature) using a stainless steel mold, A pellet having a diameter of 8 mm and a height of 1 mm was produced. In this molding step, the reactivity is improved by bringing particles into close contact with each other.

  Next, in the heating step (step S6d), the molded body was heated with the dry gas introduced into the reaction vessel. In this heat treatment, the temperature in the reaction vessel was 500 ° C., and the temperature holding time was 2 hours. The amount of dry oxygen gas introduced is 100 cc per minute. The reason why the molded body is heated to 500 ° C. in this heating step is to remove residual organic substances and completely oxidize them to increase the crystallinity of the composite oxide.

  Thereafter, in the pulverization step (step S6e), the molded body after the heat treatment was placed in an agate mortar and pulverized. As a result, an ultrafine powder 10 having an average particle size of 20 nm or less was obtained. The average particle size of the composite oxide particles was measured using a transmission electron microscope (see FIG. 10).

  Then, as shown in FIG. 3, the produced powder 10 is put into a sample cube 12, and the powder 10 is press-molded at a press pressure of 4000 MPa, so that a cylindrical composite oxide having a diameter of 5 mm and a height of 8 mm is obtained. Bulk body 16 was produced. It was found that the apparent density of the composite oxide bulk body 16 has a dense structure of about 80% or more of the theoretical value.

[Supplementary explanation regarding Examples 1 to 4]
(1) In the above-described Examples 1 to 3, the reason why the gas types in the heating process after the refluxing process (step S3: drying, steam introduction) and the cooling process (step S5) are properly used is the oxidation state of Co (cobalt). This is because of this. Before hydrolysis, cobalt is Co ²⁺ in the alkoxide, so that a dry gas is introduced for the purpose of removing the solvent while maintaining the state. The gas used may be an inert gas, and may be, for example, argon or nitrogen. In addition, since it is necessary to oxidize Co ²⁺ → Co ³⁺ in the process of introducing water vapor, water vapor is added to oxygen. Co exists as Co ^{3+ in} LiCoO ₂ which is the final target.

(2) In the production of LiCoO ₂ powder, water vapor + oxygen (humidified oxygen) was introduced in the water vapor introduction step of Example 1 (see FIG. 4), and water vapor + oxygen + argon (humidified oxygen) was introduced in the water vapor introduction step of Example 3. + Argon) is introduced (see FIG. 7), but in Example 3, the result is the same without using argon. That is, the gas species in the water vapor introduction step of Example 3 may be the same. However, oxygen is always necessary.

(3) The reason why dry oxygen is introduced after the introduction of water vapor in Example 3 is to eliminate residual organic matter.

(4) In Examples 1 to 4, the reason for using oxygen gas in the cooling step is to completely oxidize the obtained composite oxide.

(5) The type of gas used for water vapor introduction differs between the production of LiCoO ₂ powder in Examples 1 to 3 and the production of LLZ powder in Example 4 because LLZ introduces La ₂ Zr ₂ when oxygen is introduced. This is because the pyrochlore of O ₇ can be easily formed, and as a result, the target composition (Li ₇ La ₃ Zr ₂ O ₁₂ ) cannot be obtained.

  In addition, the manufacturing method of the composite oxide particles and the manufacturing method of the composite oxide bulk body according to the present invention are not limited to the above-described embodiments, and can adopt various configurations without departing from the gist of the present invention. Of course.

10 ... Powder 12 ... Sample cube 16 ... Bulk complex oxide

Claims (9)

Refluxing a mixed solution of a plurality of alkoxides and alcohol to prepare a precursor solution containing a composite alkoxide;
Heating the precursor solution in a sealed container,
The heating step includes
A composite oxidation characterized by having a water vapor introduction step of introducing water vapor into the sealed container during heating and causing at least hydrolysis of the composite alkoxide in the precursor solution to generate composite oxide particles. Method for producing product particles. In the method for producing composite oxide particles according to claim 1,
A method for producing composite oxide particles, wherein, in the steam introduction step, production of a composite solid alkoxide by hydrolysis of the composite alkoxide, dehydration condensation of the composite solid alkoxide, evaporation of a solvent, and crystallization are advanced. In the method for producing composite oxide particles according to claim 1 or 2,
In the refluxing step, the mixed solution is refluxed in the vicinity of the boiling point of the alcohol. In the manufacturing method of complex oxide particles given in any 1 paragraph of Claims 1-3,
The heating step includes a step of heating the precursor solution in the sealed container at a temperature not lower than the boiling point of the alcohol and not higher than 500 ° C., and drying and solidifying the precursor solution. Manufacturing method. In the manufacturing method of complex oxide particles given in any 1 paragraph of Claims 1-4,
In the heating step, the precursor solution is dried and solidified by heating the precursor solution to the boiling point temperature of the alcohol in a state where an inert gas is introduced into the sealed container prior to the water vapor introduction step. A method for producing composite oxide particles, comprising the step of raising the heating temperature of the precursor solution from the boiling point temperature of the alcohol to 500 ° C. at the maximum with the start of the water vapor introduction step. In the manufacturing method of complex oxide particles given in any 1 paragraph of Claims 1-5,
In the steam introduction step, the oxygen gas that has passed through the humidifier is held for 3 to 5 hours while being introduced into the sealed container. In the manufacturing method of complex oxide particles given in any 1 paragraph of Claims 1-6,
A cooling step after the water vapor introduction step;
In the cooling step, the introduction of the water vapor into the sealed container is stopped, and the temperature is lowered to room temperature while introducing oxygen gas not containing water vapor. In the manufacturing method of complex oxide particles given in any 1 paragraph of Claims 1-7,
The method for producing composite oxide particles, wherein the composite oxide particles to be produced have an average particle size of 30 nm or less. Preparing a powder containing composite oxide particles produced by the method for producing composite oxide particles according to any one of claims 1 to 8,
A method of producing a composite oxide bulk body, comprising: pressing the powder into a mold and pressing it at room temperature to form a composite oxide bulk body.

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