JP2000128514A - Preparation of lithium-containing compound - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for preparing a lithium-containing compound, which is capable of easily preparing the compound at a low temp. SOLUTION: A glass ceramic-like lithium-containing compound containing Li, Ti, Al, P and O or, further, a glass ceramic-like lithium-containing compound further containing Si is prepared by using a sol-gel method. These compounds are obtained by first dissolving raw materials of organometal or inorganic metal compounds in ethanol, then mixing them, after adding nitric acid as a catalyst, heating the mixture to 60 deg.C in order to subject the mixture to gelation via solation, thereafter, drying the formed gel, subjecting to a first heating step at a temp. of 300-600 deg.C, and successively subjecting to a second heating step at a temp. of 700-1,100 deg.C. As the sol-gel method is applied in this method, the compound is obtained at a low temp. As raw materials, lithium methoxide and titanium butoxide are preferably used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to lithium (Li)
, Titanium (Ti), aluminum (Al), and phosphorus (P)
The present invention relates to a method for producing a lithium-containing compound containing at least lithium, titanium, aluminum, phosphorus, and oxygen among silicon, silicon (Si), and oxygen (O).

[0002]

2. Description of the Related Art In recent years, with the advance of electronic technology, a large number of small portable electronic devices such as a camera-integrated VTR (video tape recorder), a mobile phone, and a laptop computer have become widespread. Have been. Therefore, as a portable power source used for them, a small and lightweight battery having a high energy density, particularly a secondary battery, is being developed. Above all, lithium secondary batteries or lithium ion secondary batteries are expected to have higher energy densities than conventional lead batteries or nickel cadmium batteries using a liquid electrolyte using water as a solvent, and are therefore highly expected. .

However, in these lithium ion secondary batteries and the like, since a liquid electrolyte in which a lithium salt is dissolved in an organic solvent has been mainly used, it is necessary to provide a means for preventing liquid leakage or a means for preventing ignition. There is a problem that it is difficult to reduce the size and thickness of the battery. Therefore, in recent years, it has been proposed to improve the safety and reliability of these lithium ion secondary batteries and the like by using an inorganic solid electrolyte instead of a liquid electrolyte using an organic solvent.
For this purpose, it is essential to develop an inorganic solid electrolyte having high ionic conductivity and being thermally and chemically stable.

For example, as a material constituting an inorganic solid electrolyte, Li ₃ N single crystal (Applied Physics Letters,
30 (1977) 621-622) or LiI-Li ₂ S-based glass (Solid State Ionics, 5 (1981 ) 663; J.Solid Sta
te Chem. 69 (1987) 252) is known. These materials have high ionic conductivity and can obtain a value of 10 ⁻³ S / cm or more at room temperature. However, on the other hand, they are difficult to manufacture, and are electrochemically and thermally incompatible. It has the disadvantage of being stable.

Therefore, the development of alternative materials has been desired. Recently, however, oxides containing lithium having a glass ceramic structure have been required to be 1.5 × at room temperature.
It was reported that a high ionic conductivity of about 10 ⁻³ S / cm was obtained (Solid State Ionics, 96 (1997) 195-
200; Japanese Patent Application Laid-Open No. 10-97811). This oxide is electrochemically and thermally stable, and is promising as a material constituting an inorganic solid electrolyte.

[0006]

However, heretofore, this oxide was conventionally produced by a melting method. Specifically, for example, after heating and melting the raw material at 1400 to 1500 ° C. for 1 to 2 hours, the first heating is performed at 680 to 800 ° C. for about 12 hours.
The target product was obtained by raising the temperature to 00 to 350 ° C. and performing the second heating for about 24 hours. Therefore, the synthesis requires a very long time and heating at a high temperature, which increases the production cost and harms the global environment.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for producing a lithium-containing compound that can easily produce a lithium-containing compound at a low temperature.

[0008]

According to the present invention, there is provided a method for producing a lithium-containing compound, comprising: a lithium-containing compound containing at least lithium, titanium, aluminum, phosphorus and oxygen among lithium, titanium, aluminum, phosphorus, silicon and oxygen. Which comprises a step of forming a sol of a raw material containing a constituent element of a lithium-containing compound and then gelling the same, and a step of heating the gelled raw material.

In the method for producing a lithium-containing compound according to the present invention, first, a raw material containing a constituent element of the lithium-containing compound is converted into a sol through a sol, and then heated.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a flowchart showing a method for producing a lithium-containing compound according to the present embodiment. Note that this method for producing a lithium-containing compound is for producing a lithium-containing compound containing at least lithium, titanium, aluminum, phosphorus, and oxygen among lithium, titanium, aluminum, phosphorus, silicon, and oxygen. A case of manufacturing a glass-ceramic state, that is, a state in which a crystal phase and an amorphous (glassy) phase are mixed will be described.

First, a raw material made of an organic metal or an inorganic compound containing a constituent element of a lithium-containing compound to be produced is prepared. For example, lithium and titanium and in the case of producing a lithium-containing compound containing aluminum and a phosphorus, lithium alkoxide, titanium alkoxide, aluminum nitrate nonahydrate _{(Al (NO 3) 3 ·} 9H 2 O) and phosphoric acid Ammonium ((NH ₄ ) ₂ HPO ₄ ) is prepared. When a lithium-containing compound containing silicon is further produced, for example, a silicon alkoxide is prepared in addition to the compound.

Here, the reason why the lithium alkoxide or the titanium alkoxide is used is that a uniform network can be easily formed and a homogeneous crystal phase can be easily precipitated. It is more preferable to use lithium methoxide (LiOCH ₃ ) as the lithium alkoxide, and it is more preferable to use titanium butoxide (TiOC ₄ H ₉ ) as the titanium alkoxide.

Next, for example, these raw materials are individually mixed and dissolved with a solvent such as ethanol (C ₂ H ₅ OH). Thereafter, they are adjusted so as to have a predetermined molar ratio, and mixed while stirring so as not to generate a precipitate abruptly (step S1). Subsequently, for example, a catalyst such as nitric acid (HNO ₃ ) is added to the mixed solution and further mixed (step S2). The catalyst may be added when each raw material is individually mixed with a solvent before forming a mixed solution.

Thereafter, for example, the mixed solution is heated to 60 ° C.
And hold for a sufficient time until complete polymerization. This causes the mixed solution to gel via sol formation (step S3). After complete polymerization, the gel is dried (step S4). This drying may be natural drying,
Heat drying may be used.

After the gel is dried, for example, the dried body is heated at a temperature in the range of 300 ° C. to 1100 ° C. and fired. At this time, for example, first, 300 ° C. or more 6
The first heating is performed at a first temperature within a range of 00 ° C. or less for about 1.5 hours to perform preliminary firing (step S5). Next, second heating is performed for 5 hours at a second temperature in a range of 700 ° C. to 1100 ° C. higher than the first temperature and firing is performed (step S6). Thereby, the lithium-containing compound described above is obtained (step S).
7).

The composition of the entire lithium-containing compound is determined according to the mixing ratio of the raw materials. The composition of the crystal phase in the lithium-containing compound is represented by the chemical formula shown in Chemical formula 1, and is determined according to the mixing ratio of the raw materials. However, the lithium-containing compound produced by the present production method may have a non-stoichiometric composition in addition to the case where the composition of the crystal phase has the stoichiometric composition shown in Chemical formula 1. Further, the ratio of the crystalline phase and the amorphous phase in the lithium-containing compound, the type of raw material, the type and amount of solvent,
It is determined by the type of the catalyst, the heating temperature, the heating time, or the heating rate.

[0018]

## STR1 ## Li _{1 + x + y} Ti _2-x Al _x P _3-y Si _y O ₁₂ where 0 <x <2, 0 ≦ y <3

As described above, according to the method for producing a lithium-containing compound according to the present embodiment, since the sol-gel method is used, it can be produced at a low temperature. Therefore, the manufacturing cost can be reduced and the influence on the environment can be reduced. In addition, the manufacturing process is simple and easy to manufacture, and the production efficiency can be improved.

Furthermore, the raw materials can be sufficiently mixed at the molecular level, and the homogeneity of the lithium-containing compound, for example, the homogeneity in the crystalline phase and the amorphous phase can be increased. Therefore, the ionic conductivity can be increased, and the unevenness in characteristics can be reduced. Therefore, for example, if the lithium-containing compound produced by this method is used for the electrolyte of a battery, the characteristics of the battery can be improved.

In addition, the particles of the crystal phase can be made fine and uniform. Therefore, even in the form of a thin film, high ionic conductivity can be obtained uniformly over the entire surface. Therefore, for example, if the lithium-containing compound produced by this method is used for the electrolyte of a battery, the thickness of the battery can be reduced. Furthermore, the composition can be easily adjusted, and a lithium-containing compound having a composition that cannot be produced by a melting method or the like can be obtained.

In addition, if a lithium alkoxide or a titanium alkoxide is used as a raw material, a uniform crystal phase can be easily obtained.

[0023]

EXAMPLES Further, specific examples of the present invention will be described in detail. The following description will be continued with reference to FIG.

First Example First, titanium butoxide, lithium methoxide, aluminum nitrate nonahydrate and ammonium phosphate were prepared as raw materials. Next, these raw materials were individually mixed and dissolved with ethanol as a solvent (step S1). In addition, at that time, for the raw materials that are not easily dissolved,
Water and nitric acid as a catalyst were added and mixed (step S
2).

Subsequently, the molar ratio of lithium, titanium, aluminum and phosphorus is lithium: titanium: aluminum:
The amount of each ethanol solution in which each raw material was individually dissolved was adjusted so that phosphorus = 24: 20: 8: 48,
They were mixed with vigorous stirring so that no precipitate formed rapidly. After that, the mixed solution was heated to 60 ° C. and held for a sufficient time until the polymerization was completed, and the mixture was gelled through sol formation (step S3). After gelation, the gel was dried (step S4). After being dried, it is heated as a first heating at 400 ° C. for 1.5 hours (step S5), and then as a second heating, at 90 ° C.
Heated at 0 ° C. for 5 hours (step S6). As a result, a powdery substance was obtained.

The obtained substance was analyzed by X-ray diffraction. As a result, a sharp peak was observed together with a gentle peak. That is, it was found that the obtained substance was a glass ceramic in which an amorphous phase and a crystalline phase were mixed. The crystal phase of the obtained substance is Li
_{1 + x} Ti _2-x Al _x (PO ₄ ) ₃ (where 0 <x <2)
It turned out that it is a lithium containing compound represented by these.
Further, the entire composition of the substance, that is, the total composition of the amorphous phase and the crystalline phase is determined by ICP (Inductively Co
(updated Plasma). As a result, it was found that the molar ratio of lithium, titanium, aluminum, and phosphorus corresponded to the mixture molar ratio of the raw materials. That is, it was found that the obtained substance was a glass-ceramic lithium-containing compound containing lithium, titanium, aluminum, phosphorus, and oxygen.

(Second Embodiment) When mixing each ethanol solution in which each raw material is individually dissolved, the molar ratio of lithium, titanium, aluminum and phosphorus is lithium: titanium: aluminum: phosphorus = 24: 23. : 5: 48, except that the respective steps were adjusted so that the ratio became 5:48. However, in this example, water and nitric acid were not added when each raw material was mixed with ethanol, but after mixing each ethanol solution in which each raw material was dissolved, nitric acid was added and mixed. Thereby, also in the present embodiment,
A powdery substance was obtained as in the first example.

The obtained substance was subjected to analysis by X-ray diffraction and chemical analysis by ICP as in the first example. As a result, similar to the first embodiment,
The obtained substance is a glass ceramic, and the crystal phase is L
It was found that the compound was a lithium-containing compound represented by i _{1 + x} Ti _2-x Al _x (PO ₄ ) ₃ . Further, it was found that the molar ratio of lithium, titanium, aluminum, and phosphorus in the whole substance corresponded to the mixture molar ratio of the raw materials.
That is, it was found that the obtained substance was a glass-ceramic lithium-containing compound containing lithium, titanium, aluminum, phosphorus, and oxygen.

(Third Embodiment) When mixing each ethanol solution in which each raw material is individually dissolved, the molar ratio of lithium, titanium, aluminum and phosphorus is lithium: titanium: aluminum: phosphorus = 24: 14. : 14: 48, except that the respective steps were adjusted to give the same steps as in the first example. However, in this example, water and nitric acid were not added when each raw material was mixed with ethanol, but after mixing each ethanol solution in which each raw material was dissolved, nitric acid was added and mixed. As a result, a powdery substance was obtained in this example as in the first example.

The obtained substance was subjected to analysis by X-ray diffraction and chemical analysis by ICP as in the first example. As a result, similar to the first embodiment,
The obtained substance is a glass ceramic, and the crystal phase is L
It was found that the compound was a lithium-containing compound represented by i _{1 + x} Ti _2-x Al _x (PO ₄ ) ₃ . Further, it was found that the molar ratio of lithium, titanium, aluminum, and phosphorus in the whole substance corresponded to the mixture molar ratio of the raw materials.
That is, it was found that the obtained substance was a glass-ceramic lithium-containing compound containing lithium, titanium, aluminum, phosphorus, and oxygen.

(Fourth Embodiment) When mixing each ethanol solution in which each raw material is individually dissolved, the molar ratio of lithium, titanium, aluminum and phosphorus is lithium: titanium: aluminum: phosphorus = 24: 5. : 23: 48, except that the respective steps were adjusted so that the ratio became 23:48. However, in this example, water and nitric acid were not added when each raw material was mixed with ethanol, but after mixing each ethanol solution in which each raw material was dissolved, nitric acid was added and mixed. Thereby, also in the present embodiment, the first
A powdery substance was obtained in the same manner as in Example 1.

The obtained substance was subjected to analysis by X-ray diffraction and chemical analysis by ICP as in the first example. As a result, similar to the first embodiment,
The obtained substance is a glass ceramic, and the crystal phase is L
It was found that the compound was a lithium-containing compound represented by i _{1 + x} Ti _2-x Al _x (PO ₄ ) ₃ . Further, it was found that the molar ratio of lithium, titanium, aluminum, and phosphorus in the whole substance corresponded to the mixture molar ratio of the raw materials.
That is, it was found that the obtained substance was a glass-ceramic lithium-containing compound containing lithium, titanium, aluminum, phosphorus, and oxygen.

(Fifth Embodiment) Tributoxyoxyphosphine (CH ₃ (CH _3
2) except for ₃ O) ₃ PO) that was performed using the same process as that of the first embodiment. However, in this example, water and nitric acid were not added when each raw material was mixed with ethanol, but after mixing each ethanol solution in which each raw material was dissolved, nitric acid was added and mixed. As a result, a powdery substance was obtained in this example as in the first example.

The obtained substance was analyzed by X-ray diffraction and chemical analysis by ICP, respectively, as in the first example. As a result, similar to the first embodiment,
The obtained substance is a glass ceramic, and the crystal phase is L
It was found that the compound was a lithium-containing compound represented by i _{1 + x} Ti _2-x Al _x (PO ₄ ) ₃ . Further, it was found that the molar ratio of lithium, titanium, aluminum, and phosphorus in the whole substance corresponded to the mixture molar ratio of the raw materials.
That is, it was found that the obtained substance was a glass-ceramic lithium-containing compound containing lithium, titanium, aluminum, phosphorus, and oxygen.

Thus, from the results of each of the examples, the sol
It has been found that by using the gel method, a lithium-containing compound containing lithium, titanium, aluminum, phosphorus, and oxygen can be produced at a low temperature.

As described above, the present invention has been described with reference to the embodiment and each example. However, the present invention is not limited to the above-described embodiment and each example, and can be variously modified. For example, in the above embodiment and each example, the case where a lithium-containing compound in the form of a glass ceramic is manufactured has been described. can do.

In each of the above embodiments, only the case where a powdery lithium-containing compound is obtained has been described. However, by adjusting various conditions, a thin-film or bulk lithium-containing compound can be obtained. .

Further, in the above-described embodiment and each example, the first heating and the second heating are performed after the gelation. However, only the first heating may be performed. Only the heating of No. 2 may be performed. In addition, heating may be performed while gradually increasing the temperature.

In addition, in the above-described embodiment and each example, the raw materials have been described with specific examples, but any compounds capable of obtaining a lithium-containing compound may be used. Furthermore, in the above-described embodiment and each example, the solvent and the catalyst have been described with specific examples. However, as long as they can function as a solvent or a catalyst, other solvents and catalysts can be used. Is also good.

In addition, in the above-described embodiment and each example, only the case where the catalyst is added has been described. However, when the sol and the gel are sufficiently formed without adding the catalyst, the catalyst is used. No addition is required. Furthermore,
In the above-described embodiment and each example, the mixed solution in which the raw materials are dissolved is heated so as to form a sol and a gel. However, a sol may be formed by mixing without heating.

[0041]

As described above, according to the method for producing a lithium-containing compound according to any one of claims 1 to 12, the raw material is turned into a sol, then gelled, and then heated. Lithium-containing compounds can be produced at low temperatures. Therefore, there is an effect that the manufacturing cost can be reduced and the influence on the environment can be reduced. In addition, there is an effect that the manufacturing process is simple and easy to manufacture, and the production efficiency can be improved.

Further, the raw materials can be sufficiently mixed at the molecular level, and the homogeneity of the lithium-containing compound can be improved. Therefore, the ionic conductivity can be increased, and the unevenness in characteristics can be reduced. Therefore, for example, when the lithium-containing compound produced by this method is used for the electrolyte of a battery, there is also an effect that the characteristics of the battery can be improved.

In addition, the crystal phase particles can be made fine and uniform. Therefore, even in the form of a thin film, high ionic conductivity can be obtained uniformly over the entire surface. Therefore, for example, if the lithium-containing compound produced by this method is used for the electrolyte of a battery, the effect of reducing the thickness of the battery can also be achieved.

Further, the composition can be easily adjusted, and an effect that a lithium-containing compound having a composition which cannot be produced by a melting method or the like can be obtained can be obtained.

In particular, according to the method for producing a lithium-containing compound according to any one of claims 6 to 10, since a lithium alkoxide or a titanium alkoxide is used as a raw material, homogeneity can be easily improved. This has the effect.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a method for producing a lithium-containing compound according to one embodiment of the present invention.

Claims (12)

[Claims] At least one of lithium (Li), titanium (Ti), aluminum (Al), phosphorus (P), silicon (Si), and oxygen (O) contains lithium, titanium, aluminum, phosphorus, and oxygen. A method for producing a lithium-containing compound, comprising: a step of forming a raw material containing a constituent element of the lithium-containing compound into a sol, followed by gelation; and a step of heating the gelated raw material. Method for producing contained compound. 2. The method for producing a lithium-containing compound according to claim 1, wherein the heating is performed at a temperature within a range of 300 ° C. or more and 1100 ° C. or less. 3. A method comprising: a first heating step of heating at a first temperature; and a second heating step of heating at a second temperature higher than the first temperature after the first heating step. The method for producing a lithium-containing compound according to claim 1, wherein 4. The method for producing a lithium-containing compound according to claim 3, wherein in the first heating step, heating is performed at a temperature within a range of 300 ° C. or more and 600 ° C. or less. 5. The method for producing a lithium-containing compound according to claim 3, wherein in the second heating step, heating is performed at a temperature within a range from 700 ° C. to 1100 ° C. 6. The method for producing a lithium-containing compound according to claim 1, wherein at least a lithium alkoxide is used as a raw material. 7. The method for producing a lithium-containing compound according to claim 6, wherein at least lithium methoxide is used as a raw material. 8. The method for producing a lithium-containing compound according to claim 1, wherein at least titanium alkoxide is used as a raw material. 9. The method for producing a lithium-containing compound according to claim 8, wherein at least titanium butoxide is used as a raw material. 10. The method for producing a lithium-containing compound according to claim 1, wherein at least lithium alkoxide and titanium alkoxide are used as raw materials. 11. The method for producing a lithium-containing compound according to claim 1, wherein the raw materials are mixed with a solvent, and ethanol is used as a solvent. 12. The method for producing a lithium-containing compound according to claim 1, wherein a catalyst is added to the raw material and nitric acid is used as the catalyst.