JP7203536B2 - Method for producing lithium ion conductive oxide - Google Patents

Description

The present invention relates to a method for producing lithium ion conductive oxides. More specifically, the present invention relates to a method for producing a lithium ion conductive oxide that can produce lithium ion conductive oxides at a lower temperature and with a higher yield than conventional methods.

_In recent years, the use of lithium-ion conductive oxides with a garnet-type structure containing lithium, lanthanum, and zirconium, such as _{Li7La3Zr2O12 ,} has been studied as a solid electrolyte in all-solid-state Li _secondary batteries. (See Patent Documents 1 to 3, etc.).
The Li ₇ La ₃ Zr ₂ O ₁₂ is usually prepared by mixing a mixture of a lithium raw material such as Li ₂ CO ₃ , a lanthanum raw material such as La ₂ O ₃ and a zirconium raw material such as ZrO ₂ at 900 to 1250 ° C. It is manufactured by repeating a firing process of firing at a high temperature of 12 to 24 hours several times.

JP 2012-18792 A JP 2012-174659 A JP 2010-143785 A

As described above, the production of _{Li7La3Zr2O12 requires} a _{high -} temperature and long-time firing process. For example, when synthesizing Li ₇ La ₃ Zr ₂ O ₁₂ by a solid-phase method using a mixed raw material obtained by mixing the lithium raw material, the lanthanum raw material, and the zirconia raw material, as shown in FIG. In the low-temperature firing of , since La ₂ Zr ₂ O ₇ and Li ₂ ZrO ₃ are also produced together with Li ₇ La ₃ Zr ₂ O ₁₂ , the yield of Li ₇ La ₃ Zr ₂ O ₁₂ is reduced. Once La ₂ Zr ₂ O ₇ and Li ₂ ZrO ₃ are produced, the firing temperature must be increased to about 1200° C. in order to obtain single-phase Li ₇ La ₃ Zr ₂ O ₁₂ having a garnet structure. I know I have to raise it. Between each firing process, it is necessary to replenish the lithium raw material, which easily evaporates at high temperatures, and this replenishment requires a step of crushing the fired product at each stage and mixing it with the lithium raw material.
Therefore, in order to improve the production efficiency of Li ₇ La ₃ Zr ₂ O ₁₂ , there is currently a demand for the development of a method that enables the sintering process to be performed at a lower temperature and a lithium ion conductive oxide to be produced in a high yield. rice field.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for producing a lithium ion conductive oxide that can produce a lithium ion conductive oxide at a lower temperature and with a higher yield than conventional methods. do.

The present invention is as follows.
[1] A spray pyrolysis step of spray pyrolyzing a raw material aqueous solution containing raw material components, and a firing step of firing a precursor composition obtained in the spray pyrolysis step, wherein the raw material aqueous solution is a chelate A method for producing a lithium ion conductive oxide, characterized by containing an agent.
[2] The method for producing a lithium ion conductive oxide according to [1], wherein a lithium salt, a lanthanum salt and a zirconium salt are used as the raw material components.
[3] The method for producing a lithium ion conductive oxide according to [1] or [2], wherein the firing temperature in the firing step is 800°C or lower.
[4] The lithium ion conductive oxide according to any one of [1] to [3], wherein the lithium ion conductive oxide is a lithium ion conductive oxide having a garnet structure containing lithium, lanthanum and zirconium. manufacturing method.
[5] Any one of claims 1 to 4, wherein the content ratio [Li:La:Zr (molar ratio)] of lithium, lanthanum and zirconium in the lithium ion conductive oxide is 7:3:2. 10. A method for producing a lithium ion conductive oxide according to claim 1.

According to the method for producing a lithium ion conductive oxide of the present invention, since the raw material aqueous solution containing the raw material components of the lithium ion conductive oxide is used, the dissociation of the raw material components in water dissociates the metal ions that make up the raw material components. Dispersibility is enhanced. In addition, since the raw material aqueous solution contains a chelating agent, the metal ions are coordinated to adjacent positions via the chelating agent. A precursor composition composed of particles obtained by misting such a raw material aqueous solution and thermally decomposing this mist is composed so as to have a high reaction activity for producing a lithium ion conductive oxide. Therefore, by performing the firing step of firing the powder made of such a precursor composition, it is possible to produce a lithium ion conductive oxide at a lower temperature and with a higher yield than before.
In addition, when the firing process is performed in a temperature range of 800° C. or less, which is lower than conventionally, transpiration of the lithium raw material can be suppressed, and production efficiency can be improved.
In addition, when the raw material aqueous solution contains lithium salt, lanthanum salt and zirconium salt as raw material components, or when the lithium ion conductive oxide has a garnet structure containing lithium, lanthanum and zirconium, or when lithium and When the content ratio of lanthanum and zirconium (Li:La:Zr) is 7:3:2 in terms of molar ratio, a lithium ion conductive oxide having excellent lithium ion conductivity can be obtained with even higher production efficiency. be able to.

It is a schematic diagram for demonstrating a spray pyrolysis apparatus. FIG. 2 is an X-ray diffraction pattern diagram of sintered compositions P11 to P13 according to this example. FIG. 4 is an X-ray diffraction pattern diagram of fired compositions P14 and P15 according to the present example. FIG. 4 is an X-ray diffraction pattern diagram of sintered compositions P21 to P23 according to comparative examples. It is a figure which shows the X-ray-diffraction pattern of the baking composition by the conventional manufacturing method.

The present invention will be described in detail below.
[Lithium ion conductive oxide]
First, the lithium ion conductive oxide according to the present invention will be described.
The lithium ion conductive oxide produced by the present invention is known to be a promising material as a solid electrolyte material for realizing an all-solid lithium ion secondary battery because of its excellent lithium ion conductivity. The lithium ion conductive oxide may be composed of a metal composite oxide containing lithium and have a garnet-type crystal structure (general formula: A ₃ B ₂ C ₃ O ₁₂ ). For example, it can be represented by the following formula (1) in which a predetermined element occupies the A site and the B site, and Li occupies the C site and the interstitial position.
_{LixAyBzOw ( 1 )}
However, x is in the range of 5≤x≤8, y is in the range of 2.5≤y≤3.5, z is in the range of 1.5≤z≤2.5, and w is in the range of 10≤w≤14.
The A site may be occupied by one or more metal elements selected from La, Al, Y, Pr, Nd, Sm, Lu, Mg, Ca, Sr and Ba.
The B site may be occupied by one or more elements selected from Zr, Hf, Nb and Ta.

Among the above, the lithium ion conductive oxide may be a composite oxide containing lithium, lanthanum and zirconium and having a garnet-type (crystal) structure. For example, it may have a garnet-type structure containing La ³⁺ at the A site, Zr ⁴⁺ at the B site, and Li ⁺ at the C site and the interstitial position.
In the above, the lithium ion conductive oxide contains lithium, lanthanum, and zirconium, and the content ratio [Li:La:Zr] of each is ₇ :3:2 in terms of molar ratio. La ₃ Zr ₂ O ₁₂ (hereinafter also simply referred to as “LLZ”) is preferred.
Other preferred examples of _{lithium ion} conductive _{oxides include Li4AlLa3Zr2O12} , _{Li5La3Nb2O12 , Li5La3Ta2O12 , Li5La3 ( Nb , Ta} ) ₂ O ₁₂ , Li ₆ (BaLa ₂ ) Ta ₂ O ₁₂ and the like.

[Method for producing lithium ion conductive oxide]
Next, the method for producing the lithium ion conductive oxide of the present invention will be specifically described.
The method for producing a lithium ion conductive oxide of the present invention includes a spray pyrolysis step of spray pyrolyzing a raw material aqueous solution (S1) containing raw material components, and a precursor composition (PRE1) obtained in the spray pyrolysis step. and a baking step of baking the raw material aqueous solution (S1), characterized in that it contains a chelating agent.

(Raw material aqueous solution)
The raw material aqueous solution S1 is a solution in which the raw material components forming the lithium ion conductive oxide and the chelating agent are dissolved in water.

The raw material components are metal salts or salts of lithium and metal elements or elements occupying the A site or the B site in the above formula (1). Each metal salt, salt, or lithium salt that occupies the A site, B site, or C site of the garnet structure may be a water-soluble salt. That is, each metal salt is not particularly limited as long as it is water-soluble, and specific examples include nitrates, sulfates, halides, hydroxides, phosphates, carbonates, acetates, oxalates, and the like. can be exemplified. These metal salts and the like may be used alone or in combination.

Specifically, if it is a raw material component of the above lithium, lithium salts such as LiNO ₃ , Li ₂ O, Li ₂ SO ₄ , LiCl, LiI, LiOH, Li ₂ CO ₃ , lithium acetate, and lithium oxalate can be mentioned. .
In addition, lanthanum salts such as La(NO ₃ ) ₃ , La ₂ (SO ₄ ) ₃ , LaCl ₃ , La(OH) ₃ and lanthanum acetate can be used as raw material components of lanthanum.
Zirconium salts such as ZrO(NO ₃ ) ₂ , Zr(SO ₄ ) ₂ , ZrCl ₄ , ZrOCl ₂ , ZrI ₄ , zirconium acetate, and zirconium acetate oxide can be used as raw material components of zirconium.
In addition to the above, aluminum salts such as Al(NO) ₃ , Al ₂ (SO ₄ ) ₃ , and AlCl ₃ can be used as raw material components of aluminum.
Niobium salts such as Nb(C ₅ H ₇ O ₂ ) ₅ and niobium chloride can be used as raw material components of niobium.
In addition, each of the above metal salts may be a hydrate.

By using a water-soluble metal salt or the like as a raw material component, the metal element or each cation of the element constituting the lithium ion conductive oxide is uniformly dispersed in the raw material aqueous solution. Therefore, it contributes to the improvement of the yield of the lithium ion conductive oxide having a garnet structure excellent in lithium ion conductivity, and the productivity can be improved.

As described above, when the lithium ion conductive oxide contains lithium, lanthanum and zirconium, the content ratio [Li: La: Zr (molar ratio)] of lithium, lanthanum and zirconium in the lithium ion conductive oxide is the target The mixing ratio of each raw material component is adjusted so that the composition ratio of Specifically, the content ratio of lithium, lanthanum, and zirconium [Li:La:Zr (molar ratio)] is (6 to 8): (4 to 2): (3 to 1) [especially (6.5 ~7.5): (2.5-3.5): (1.5-2.5), further (6.8-7.2): (2.8-3.2): (1 .8 to 2.2)].
In addition, the total of the raw material components (mixed raw material component) obtained by adjusting the mixing ratio of each raw material component so that the lithium component, the lanthanum component and the zirconium component have the above molar ratio is the concentration in the raw material aqueous solution, which is the volume of lithium The molar concentration may be in the range of 0.01 to 5 mol/L, preferably 0.1 to 1 mol/L, more preferably 0.3 to 0.8 mol/L.

The chelating agent is not particularly limited as long as it has a conformation to which a cation such as a metal is coordinated. However, since it is easily thermally decomposed, it may be an organic chelating agent. For example, carboxylic acids having 2 to 12 carbon atoms, phenols, hydroxycarboxylic acids, diketones, aminocarboxylic acids and the like are preferable. α-Hydroxycarboxylic acids such as lactic acid, glycolic acid, citric acid, gluconic acid, malic acid, tartaric acid and salicylic acid are more preferred.
Multiple types of cations constituting the lithium ion conductive oxide should be coordinated more uniformly and in close proximity via the chelating agent in the raw material aqueous solution. is more preferable, and among the above agents, citric acid is preferable.

Moreover, the mixing ratio of the chelating agent to each raw material component can be expressed as the content ratio of the chelating agent to the lithium component based on the content ratio of the lithium component in the mixed raw material component. Specifically, when 1 mol of the chelating agent produces 1 to 5 conformations, [Li: chelating agent (molar ratio)] is (6 to 8): (5.6 to 7.6 ) [especially (6.5 to 7.5): (6.1 to 7.1), further (6.8 to 7.2): (6.4 to 6.8)] .
Further, the chelate-containing mixed raw material obtained by mixing the chelating agent adjusted to the above ratio with respect to the lithium component and the mixed raw material component has a concentration in the raw material aqueous solution that is the molar concentration of the chelating agent, It may be in the range of 0.01 to 5 mol/L, preferably 0.1 to 1 mol/L, more preferably 0.3 to 0.7 mol/L.

[Spray pyrolysis step]
The spray pyrolysis process will be described with reference to FIG.
In the spray pyrolysis step, first, the raw material aqueous solution of the lithium ion conductive oxide is sprayed to generate a mist of the raw material aqueous solution. Next, synthetic particles are obtained by thermally decomposing the mist of the raw material aqueous solution.
For example, the raw material aqueous solution S1 is supplied to the misting device 12 to generate a mist M of the raw material aqueous solution S1. Next, the mist M is thermally decomposed within the reaction unit 15 . The synthetic particles 17 obtained as a result of the thermal decomposition reaction are used as the precursor composition PRE1 for firing in the next firing step.

(Spray pyrolysis equipment)
The spray pyrolysis step is performed, for example, by a spray pyrolysis apparatus 10 shown in FIG. The spray pyrolysis apparatus 10 includes a misting device 12, a reaction unit 15, a carrier gas supply device 14, a collector 16, and the like.
When the spray pyrolysis apparatus 10 is used in the spray pyrolysis step, the raw material aqueous solution S1 is misted, and the mist M is supplied to the reaction unit 15 together with the carrier gas (the flow is indicated by the white arrow in FIG. 1). The mist M supplied to the reaction unit 15 is thermally decomposed while passing through the reaction unit 15 together with the flow of carrier gas to generate particles having a predetermined composition. The particle-containing gas containing the particles is discharged from the reaction unit 15 and reaches the collector 16 , where the carrier gas is separated and synthesized particles 17 are collected. The synthetic particles 17 are the precursor composition PRE1 according to the invention for firing in the firing step.

The misting device 12 may be any device as long as it mistizes the raw material aqueous solution S1. The misting method is not particularly limited, but various modes such as a nozzle system using a spray nozzle such as a two-fluid nozzle or a pressure spray nozzle, and an ultrasonic system can be employed.
The reaction unit 15 is not particularly limited, and various known forms can be appropriately adopted. The heating means is not particularly limited, and for example, a heater or the like may be used, which is shown as a heater 13 in FIG.
The temperature of the reaction unit 15 can be set appropriately to obtain the desired synthetic particles using a heating means. For example, the temperature of the reaction unit 15 may be set so that the temperature increases stepwise from the inlet to the outlet of the reaction unit. . In the case of the reaction unit 15 illustrated in FIG. 1, the inlet temperature is set to 150 to 300° C., then 300 to 500° C., then 500 to 700° C., and the outlet temperature is set to 600 to 850° C. by the four-stage heater 13. You can raise it step by step.
In addition, the carrier gas supply device 14 is configured to be adjustable to a predetermined air pressure in order to supply carrier gas for uniformly circulating a required amount of mist M in the reaction tube 151 . The carrier gas may be ambient air or gas from a particular gas source. The method of supplying the carrier gas is not particularly limited, and an air supply pump may be used. may
The collector 16 collects synthetic particles 17 obtained by thermally decomposing the mist M of the raw material aqueous solution S1. Synthetic particles 17 obtained by thermal decomposition of the mist M are usually particles having an average particle diameter of about 1 μm or less, and are contained in high-temperature gas within the reaction unit 15 . The collector 16 is not particularly limited as long as it can separate the gas from the particle-containing gas and collect the synthetic particles 17. For example, a dust collector may be used.

[Baking process]
In the baking step, the precursor composition PRE1 composed of the synthetic particles 17 obtained in the spray pyrolysis step is baked.
The firing method is not particularly limited. For example, the powder of the precursor composition may be further wet mixed. In addition, the precursor composition may contain various additives as long as the effects of the present invention are not impaired. Specific additives include, for example, sintering aids, texture control agents, molding aids, and the like. These additives may be used singly or in combination of two or more.

The firing temperature in this firing step is preferably 600 to 800°C, more preferably 650 to 800°C, particularly preferably 700 to 800°C. When the firing temperature is within this range, the precursor composition can be sufficiently reacted to improve the yield of the single-phase lithium ion conductive oxide, and the evaporation of the lithium raw material can be sufficiently suppressed. .
The firing time is preferably 1 to 20 hours, more preferably 2 to 12 hours, even more preferably 3 to 8 hours, particularly preferably 4 to 6 hours. When the firing time is within this range, the precursor composition can be sufficiently reacted, and the evaporation of the lithium raw material can be sufficiently suppressed.
Moreover, the firing atmosphere is not particularly limited, and may be an air atmosphere, an inert gas atmosphere such as nitrogen gas or argon gas, or the like.

EXAMPLES Hereinafter, the present embodiment of the method for producing a lithium ion conductive oxide will be described more specifically with reference to examples. However, the present invention is by no means restricted to these examples.

"Example"
[1. Spray pyrolysis process]
After adjusting the raw material aqueous solution S1 containing the raw material components and the chelating agent by the method described below, the raw material aqueous solution S1 is subjected to spray pyrolysis using the spray pyrolysis apparatus 10 shown in FIG. A precursor composition PRE1 consisting of a thermal decomposition product (synthetic particles 17) was obtained.

(Preparation of raw material aqueous solution)
The raw material components include lithium nitrate [LiNO ₃ ] as the Li source, lanthanum nitrate hexahydrate [La(NO ₃ ) _{3.6H 2} O] as the La source, and zirconium nitrate [ZrO(NO ₃ ) ₂ as the Zr source. ] and prepared citric acid as a chelating agent. LiNO ₃ : La(NO ₃ ) ₃ : ZrO(NO ₃ ) ₂ : citric acid in a molar ratio of 7:3:2:6.7, containing each raw material component and a chelating agent A mixed powder was prepared. Next, distilled water was added to this mixed powder to obtain a raw material aqueous solution S1 in which each raw material component and a chelating agent were uniformly dissolved in distilled water. The concentration of the raw material aqueous solution S1 was adjusted so that the molar concentration of Li was 0.35 mol/L.

(spray pyrolysis)
The raw material aqueous solution S1 was supplied to the mist generator 12, and the ultrasonic wave generator 121 was used to generate a mist M of the raw material aqueous solution S1. Air was used as a carrier gas, and the carrier gas Air was supplied into the reaction tube 151 arranged in the reaction unit 15 . That is, the carrier gas supply device 14 was adjusted so that the mist M could be supplied to the reaction tube 151 together with the carrier gas Air. Specifically, the air pressure of the carrier gas Air was adjusted so that the flow rate of the mist M flowing through the inlet flow path 153 was 10 L/min. The temperature of the reaction unit 15 was set using four heaters 13 from the inlet to the outlet along the reaction tube 151, and adjusted to 200°C-300°C-500°C-800°C in order from the inlet.
Synthetic particles 17 after the pyrolysis reaction generated while the mist M was flowing through the reaction tube 151 were collected by the collector 16 . The obtained synthetic particles 17 made of the thermal decomposition product of the mist M were dried to obtain a powder of the precursor composition PRE1.

[2. Firing process]
The resulting precursor composition PRE1 was placed in a crucible, heated in an electric furnace for 2 hours, and then naturally cooled to obtain the target fired composition.
That is, the temperature for firing the precursor composition PRE1 is set to each temperature of T1 to T3 (700 ° C., 750 ° C., 800 ° C.), and the firing step is performed for 2 hours. P13 (corresponding to temperatures T1-T3) was obtained.
In addition, the time for firing the precursor composition PRE1 is set to each time of H1 and H2 (2 hours, 12 hours), and the firing step of firing at 700 ° C. is performed, respectively, to obtain the desired fired compositions P14 and P15. (corresponding to times H1 and H2) were obtained.

<<Comparative example>>
Lithium nitrate [LiNO ₃ ], lanthanum nitrate hexahydrate [La(NO ₃ ) _{3.6H 2} O], and zirconium nitrate [ZrO(NO ₃ ) and ₂ ] were prepared, and a raw material mixed powder was weighed so that the molar ratio was 7:3:2 to prepare a raw material aqueous solution S2 (not shown). That is, the raw material aqueous solution S2 of the comparative example was obtained in the same manner except that the aqueous solution was adjusted without containing citric acid. Next, using the raw material aqueous solution S2, the spray pyrolysis step was performed in the same manner as in the example to obtain the powder of the precursor composition PRE2 in the same manner.
Next, the precursor composition PRE2 thus obtained was subjected to the above firing step in the same manner as in the example.
That is, firing compositions P21 to P23 ( corresponding to temperatures T1 to T3) were obtained.

[3. X-ray diffraction]
A portion of each fired composition obtained was taken out and subjected to X-ray diffraction. The results are shown in FIGS. 2 to 4 together with the X-ray diffraction results of the precursor compositions PRE1 and PRE2.

(a) From FIG. 2, the following can be understood The X-ray diffraction pattern of the precursor composition PRE1 shows that the diffraction peaks of pyrochlore marked with a circle appear in the figure. Therefore, it can be seen that the precursor composition PRE1 is mainly a pyrochlore phase composition.
Moreover, the X-ray diffraction patterns of the fired compositions P12 and P13 show that the diffraction peaks of garnet-type LLZ marked with ● appear mainly in the figure. Therefore, it can be seen that the fired compositions P12 and P13 produced single-phase garnet-type LLZ.
The X-ray diffraction pattern of calcined composition P11 also shows that the relative proportion of pyrochlore diffraction peaks is reduced compared to precursor composition PRE1. Furthermore, other peaks than the diffraction peak indicating pyrochlore are also generated, indicating that the other peaks appear at angles corresponding to 2θ marked with the above-mentioned ● mark. Therefore, it can be seen that the fired composition P11 is a composite composition that mainly produces pyrochlore but also contains garnet-type LLZ.

As described above, the precursor composition PRE1 subjected to the spray pyrolysis step mainly generates a pyrochlore phase, but after that, by performing a firing step at a firing temperature of 700 ° C. for 2 hours, a garnet-type structure is partially formed. It can be seen that it produces LLZ. In addition, it can be seen that as the firing temperature is further increased to 750 to 850° C., the yield of single-phase garnet-type LLZ crystals is increased by carrying out the firing process for 2 hours.

(b) Fig. 3 reveals the following: The X-ray diffraction pattern of the fired composition P15 shows that the diffraction peaks of the garnet-type LLZ marked with ● appear in the figure. Therefore, it can be seen that the fired composition P15 produced a single-phase garnet-type LLZ.
In addition, when the X-ray diffraction pattern of the fired composition P14 is compared with the peak of PRE1, other peaks other than the diffraction peaks marked with ○ indicating pyrochlore are generated, and the other diffraction peaks are marked with the above mark. It is shown to appear slightly at the angle corresponding to 2θ. Therefore, it can be seen that the fired composition P14 is a composite composition that mainly produces pyrochlore and slightly produces garnet-type LLZ.

From the above, it can be seen that by using the precursor composition PRE1 and performing the firing process at a firing temperature of 700° C. for 2 hours, a fired composition P14 that partially generates garnet-type LLZ can be obtained. Furthermore, it can be seen that the probability of forming the fired composition P15 as single-phase garnet-type LLZ crystals is increased by performing the firing step with the firing time extended to 12 hours.

(c) Fig. 4 reveals the following: The X-ray diffraction pattern of the precursor composition PRE2 shows the diffraction peaks of pyrochlore marked with a circle in the figure. Therefore, it can be seen that the precursor composition PRE2 is mainly a pyrochlore phase composition.
In addition, the X-ray diffraction pattern of the fired composition P21 has a diffraction peak of lanthanum oxide [La ₂ O ₃ ] marked with a triangle in the figure and a lithium zirconate [Li ₂ ZrO ₃ ] marked with a triangle in the figure. ] appears. Therefore, it can be seen that the fired composition P21 is a composite composition mainly containing lanthanum oxide and containing lithium zirconate.
In addition, the X-ray diffraction pattern of fired composition P22 shows that the diffraction peak of lanthanum oxide is smaller than that of fired composition P21, and the diffraction peak of lithium zirconate appears as in fired composition P21. In addition, in the fired composition P22, in addition to the diffraction peaks representing lanthanum oxide and lithium zirconate, other peaks other than these are generated, and the other diffraction peaks are the angles corresponding to 2θ marked with the above It shows that it is represented by
Therefore, it can be seen that the fired composition P22 is a composite composition that mainly contains lanthanum oxide and produces lithium zirconate and LLZ.
Moreover, the X-ray diffraction pattern of the fired composition P23 shows that the diffraction peak of garnet-type LLZ appears. Therefore, it can be seen that the fired composition P23 is a single-phase garnet-type LLZ composition.

[4. evaluation]
From the results of FIG. 4 of the above (c), in the comparative example, when the raw material aqueous solution S2 does not contain citric acid, after performing the spray pyrolysis step, the precursor composition PRE2 is baked for 2 hours at a baking temperature of 800 It can be seen that a garnet-type single-phase LLZ can be obtained by performing the firing process at °C.
On the other hand, in this example, from the results of FIG. 2 of (a) above, the precursor composition PRE1 obtained by performing the spray pyrolysis step contains pyrochlore as a main component as in the comparative example of (c). It can be seen that a garnet-type single-phase LLZ can be obtained by firing the precursor composition PRE1 at a firing time of 2 hours and a firing temperature of 750°C. The production method of the present example is preferable in that garnet-type single-phase LLZ can be obtained at a lower temperature and with a high yield.
Further, from the results of FIG. 3 of (b) above, even if the firing temperature in the firing step is as low as 700° C., if the firing time is 12 hours, a garnet-type single-phase LLZ can be obtained from the precursor composition PRE1. I understand. It is preferable in that garnet-type single-phase LLZ can be obtained at a lower temperature than firing at 750° C. for 2 hours without impairing the yield.

As described above, the present example is preferable from the viewpoint of improving production efficiency, because the garnet-type single-phase LLZ can be produced in a high yield with a small number of man-hours for firing the precursor composition PRE1.
In addition, by performing a firing step of firing for 2 to 12 hours at a temperature range of about 700 ° C. to 800 ° C., garnet-type single-phase LLZ can be produced with good yield, and the transpiration suppression effect of the lithium raw material can be obtained. It is preferable in that it is
Furthermore, by performing a firing process in a temperature range of about 700 ° C. to 800 ° C., a garnet-type single-phase LLZ can be generated. This is preferable in that it is advantageous when considering the manufacturing method of the battery.

The method for producing a lithium ion conductive oxide of the present invention can be suitably used in the field of electrochemical devices such as lithium ion secondary batteries.

Claims (4)

In a method for producing a _lithium ion conductive oxide that is _Li7La3Zr2O12 having a garnet-type (crystalline ) _{structure ,}
A spray pyrolysis step of spray pyrolyzing a raw material aqueous solution containing lithium salt, lanthanum salt and zirconium salt, a chelating agent, and water as raw material components;
A firing step of firing the precursor composition obtained in the spray pyrolysis step,
In the spray pyrolysis step, while flowing the mist of the raw material aqueous solution with a carrier gas, the initial heating temperature of the mist is 150 ° C. to 300 ° C., and the final heating temperature is 600 ° C. to 850 ° C. while heating in an environment set to a high temperature,
The method for producing a lithium ion conductive oxide, wherein the firing temperature in the firing step is 700°C to 800°C. The lithium salt is LiNO ₃ , Li ₂ O, Li ₂ SO ₄ , LiCl, LiI, LiOH, Li ₂ CO ₃ , lithium acetate and lithium oxalate. The lanthanum salt is La(NO ₃ ) ₃ , La ₂ (SO ₄ ) ₃ , LaCl ₃ , La(OH) ₃ and lanthanum acetate. The zirconium salt is ZrO(NO ₃ ) ₂ , Zr(SO ₄ ) ₂ , ZrCl ₄ , ZrOCl ₂ , ZrI ₄ , zirconium acetate and zirconium acetate oxide.

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