JPH09309726A - Lithium titanate hydrate and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently produce lithium titanate hydrate excellent in crystallinity by reacting a titanic acid compound obtained by reacting a titanium compound with an ammonium compound in water with a lithium compound in water. SOLUTION: A titanium compound is reacted with an ammonium compound in water at 0-50 deg.C to afford a titanic acid compound. Then, the titanic acid compound is reacted with a lithium compound, as necessary, in water containing 0.01-5mol/l ammonium compound at 50 deg.C to provide flaky or plate-like lithium titanate having laminate structure with 1-300m<2> /g specific surface area and 0.1-50μm longest particle diameter.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a lithium titanate hydrate which is a compound useful as a precursor of lithium titanate and a method for producing the same.

[0002]

2. Description of the Related Art Lithium titanate, which is useful as a negative electrode for lithium batteries, is a compound represented by the general formula Li _X Ti _Y O ₄ , and a typical compound is Li _2.67 Ti.
_1.33 O ₄ , LiTi ₂ O ₄ , Li _1.33 Ti _1.67 O ₄ , L
i _1.14 Ti _1.71 O ₄ . In order to obtain this lithium titanate, a method of heat-treating a mixture of a titanium oxide powder and a lithium compound powder at a temperature of 700 to 1600 ° C. is used (see Japanese Patent Application Laid-Open No. 6-275263).

[0003]

Since the lithium titanate obtained by the above-mentioned prior art method is a sintered body in which sintering between particles has occurred unevenly, the size and shape of the particles cannot be controlled. There's a problem. Furthermore, since the reaction for obtaining lithium titanate is a solid-solid reaction between the titanium oxide powder and the lithium compound powder, the reactivity is poor even if heat treatment is performed at a high temperature, and there is also a problem that a large amount of raw material powder remains. On the other hand, a mixture of titanium oxide and a lithium compound
Even if it heat-processes at a low temperature of 00 degreeC or less, there exists a problem that reaction will not progress and lithium titanate cannot be obtained.

[0004]

The present inventors have improved the state of a mixture of titanium oxide powder and lithium compound powder before heat treatment in order to obtain lithium titanate in which the size and shape of particles are controlled. As a result of various investigations so as to obtain a titanate compound by reacting a titanium compound with an ammonium compound in water, and then reacting the titanate compound with a lithium compound in water, the size and shape of particles are controlled. That the desired lithium titanate is obtained by heat treating this lithium titanate hydrate,
After further examination, the present invention was completed.

That is, the present invention provides a lithium titanate hydrate having a flaky or plate-like particle shape, and further a lithium titanate hydrate having a controlled particle size. The present invention also provides a method for efficiently obtaining the lithium titanate hydrate.

[0006]

DETAILED DESCRIPTION OF THE INVENTION The present invention has the general formula Li _X Ti _Y O
_{The present} invention relates to a lithium titanate hydrate represented by ₄ · nH ₂ O, wherein even a single phase of lithium titanate hydrate is a mixed state of lithium titanate hydrate and titanium oxide. It may also contain a small amount of impurities such as hydrogen and ammonia. X and Y in the general formula
The value of is expressed by the value of X / Y, and the value in the range of 0.5 to 2 is a value that gives a preferable composition. The lithium titanate hydrate of the present invention is characterized by having a flaky or plate-like particle shape, and the particle shape is controlled. When the lithium titanate hydrate particles have a flaky or plate-like particle shape, lithium titanate capable of promptly doping and dedoping lithium ions can be obtained, which is a preferable shape. In this flaky or plate-like shape, scale, mica, thin film,
It includes a shape called a thick film, and such a particle shape can be confirmed by observation with an electron microscope. Further, the lithium titanate hydrate of the present invention may have a laminated structure in which two or more particles having a flaky or plate-like shape are stacked. From the lithium titanate hydrate having such a laminated structure, lithium titanate having a similar laminated structure can be obtained, which can trap a substance or ion such as lithium between the layers, It is particularly preferable because it has excellent characteristics when used as a negative electrode material for batteries. The specific surface area of the lithium titanate hydrate is preferably in the range of 1 to 300 m ² / g, more preferably in the range of 5 to 300 m ² / g, and most preferably in the range of 10 to 300 m ² / g. .

The preferred lithium titanate hydrate of the present invention is one in which the size is controlled in the form of fine particles. The particle diameter (longest diameter) can be appropriately designed, but it is 0.1 to 50 μm because lithium titanate excellent in characteristics when used as a negative electrode material of a lithium battery can be obtained.
Is a preferable range, and 0.2 to 30 μm is a more preferable range. Further, the lithium titanate hydrate of the present invention preferably has excellent crystallinity, which can be confirmed by X-ray diffraction.

Next, the present invention is a method for producing a lithium titanate hydrate, which comprises reacting a titanium compound and an ammonium compound in water to obtain a titanate compound,
It is characterized by comprising a step of reacting the titanic acid compound and a lithium compound in water. First, the above-mentioned step is a step of obtaining a compound of titanic acid, and as the titanium compound used therefor, an inorganic titanium compound such as titanium sulfate, titanyl sulfate or titanium chloride, or an organic titanium compound such as titanium alkoxide can be used. Particularly, titanium chloride is preferable because it can reduce the amount of impurities remaining in lithium titanate. Further, as the ammonium compound, aqueous ammonia, ammonium carbonate, ammonium sulfate, ammonium nitrate or the like can be used. When an alkali metal compound such as a sodium compound or a potassium compound is used instead of the ammonium compound, elements of sodium and potassium remain in the obtained titanate compound, and the particles between particles during the subsequent heat treatment for obtaining lithium titanate are used. Sintering is caused, and the size and shape of the particles tend to be non-uniform. The reaction proceeds by mixing the titanium compound and the ammonium compound in water, and orthotitanic acid (H ₄ TiO ₄ ) or H _{4 -n} (N ₄ N in which its hydrogen ion is replaced with ammonium ion)
H ₄₎ titanate compound is a compound represented by _n TiO ₄ can be obtained. The replacement amount of ammonium ions in H _4-n (NH ₄ ) _n TiO ₄ can be arbitrarily changed by adjusting conditions such as ammonium ion concentration, free hydroxyl group concentration, hydrogen ion concentration and reaction temperature during the reaction. Since the particle size of the obtained titanic acid compound affects the particle size of the lithium titanate hydrate obtained in the subsequent step, when the reaction temperature is set in the range of 0 to 50 ° C., fine particles are obtained. This is preferable because a titanic acid compound can be obtained and further fine particle lithium titanate hydrate can be obtained. A more preferable temperature range is 5 to 40 ° C, and a most preferable temperature range is 10 to 30 ° C.

The titanic acid compound thus obtained may be filtered, washed, acid washed, or dried, if necessary.

The next step is a step of obtaining a lithium titanate hydrate using the titanic acid compound obtained in the above step, which is a step of reacting the titanic acid compound and the lithium compound in water. is there. As the lithium compound, a water-soluble lithium compound such as lithium hydroxide, lithium carbonate, lithium nitrate, and lithium sulfate can be used. The reaction proceeds by mixing the lithium compound and the titanate compound in water. When the temperature of this reaction is 50 ° C. or higher, lithium titanate hydrate having excellent crystallinity can be obtained, which is preferable. A more preferred temperature range is 100 ° C. or higher, an even more preferred temperature range is 100 to 250 ° C., and a most preferred temperature range is 130 to 200 ° C. When the reaction is carried out at a temperature of 100 ° C. or higher, it is preferable that the lithium compound and the titanate compound are placed in an autoclave and subjected to hydrothermal treatment under a saturated vapor pressure or under a pressure. It is more preferable that the hydrothermal treatment be performed in the presence of an ammonium compound, since a lithium titanate hydrate having good crystallinity and a well-formed shape can be obtained even at a lower hydrothermal treatment temperature. Ammonia water, ammonia gas, ammonium carbonate, ammonium sulfate, ammonium nitrate and the like can be used as the ammonium compound present during the hydrothermal treatment. The amount of the ammonium compound to be present is about 0.01 to 5 mol / l,
It is preferably 0.1 to 3 mol / l. By such a hydrothermal treatment, a lithium titanate hydrate having a laminated structure can be obtained.

The lithium titanate hydrate thus obtained may be filtered and, if necessary, washed or dried. The drying temperature can be appropriately set as long as the temperature is lower than the temperature at which lithium titanate hydrate releases water of crystallization, and a temperature of about 30 to 200 ° C. is appropriate.

The lithium titanate hydrate thus obtained is heat-treated at a temperature of about 200 to 1300 ° C. to obtain lithium titanate.

[0013]

EXAMPLES Examples of the present invention will be shown below, but the present invention is not limited to these examples.

Example 1 (1) Synthesis of titanic acid compound In a 5 l 4-necked flask, 28% by weight of aqueous ammonia 91 was added.
1 ml and 1339 ml of pure water were added, and while stirring, ice-cooling was performed so that the temperature of the solution became 10 to 15 ° C., and 1.25
2250 ml of a mol / l titanium tetrachloride aqueous solution was added over 2 hours and then aged for 1 hour to obtain a precipitate. The pH after aging is 8.85 and the TiO ₂ concentration is 50 g / l.
And the free hydroxyl group concentration was 0.5 mol / l.

Next, an aqueous hydrochloric acid solution prepared by diluting 199 ml of 35% by weight hydrochloric acid with 300 ml of pure water was added to the above aged slurry over 1 hour to adjust the pH to 5.50, and then the pH was adjusted to 5.50. Aged for 1 hour while holding. Thereafter, the precipitate was filtered and washed to remove ammonia and chloride ions, and the obtained filter cake was repulped to T
A slurry having an iO ₂ concentration of 50 g / l was obtained. Then, while cooling with ice, 26 ml of 35% by weight hydrochloric acid was added to the slurry.
After adjusting the pH to 5.50 by adding a hydrochloric acid aqueous solution diluted with 104 ml of pure water over 1 hour, the mixture was aged for 1 hour while maintaining the pH, and then the precipitate was filtered and washed, A titanic acid compound was obtained.

A small amount of the titanic acid compound thus obtained was dried at a temperature of 50 ° C. and its physical properties were investigated. As a result, this titanic acid compound was an aggregate of fine particles (amorphous form), and was amorphous in X-ray. According to the chemical analysis, the component ratio was 47.0% by weight of Ti, N
H ₄ 1.44 wt%, a Cl 0.07 wt%, the composition is estimated to H _3.92 (NH ₄₎ a _0.08 TiO _4. Further, DSC analysis revealed that the polymer was dehydrated at 111 ° C. and crystallized into anatase at 440 ° C.

(2) Synthesis of Lithium Titanate Hydrate The titanate compound obtained in (1) above is repulped to give T.
A slurry having an iO ₂ concentration of 55.02 g / l was obtained. The pH of this slurry was 6.90 and the conductivity was 330 μS /
cm. 3.64 l of this slurry was charged into a 5-l4 neck flask, and while cooling the ice with ice so that the temperature of the slurry was 10 to 15 ° C, an aqueous solution in which 84.97 g of lithium hydroxide monohydrate was dissolved in 360 ml of pure water was added. It was added over time and then aged for 1 hour. After completion of the addition, the pH of the slurry was 12.1, and the TiO ₂ concentration was 50 g / l. The added lithium compound is Li / Ti
The molar ratio was 0.8. Next, the slurry thus obtained was charged into an autoclave and hydrothermally treated at a temperature of 190 ° C. for 2 hours. The slurry after the hydrothermal treatment was thickened into a paste, had a pH of 13, and had an ammonia odor. Next, the hydrothermally treated slurry was filtered and then dried at a temperature of 50 ° C. without washing to obtain a lithium titanate hydrate (Sample A) of the present invention.

The physical properties of the sample A thus obtained were examined. As a result, this lithium titanate hydrate had a long diameter of 1 μm and a short diameter of 0.8 μm as observed by an electron microscope.
It was found that the fine particles had an extremely thin plate-like shape with a thickness of about 16 nm and had a laminated structure in which about 4 layers were stacked in the thickness direction, and the layer interval was about 4 nm. The specific surface area is 105.2 m ² / g and the void volume is 0.386 m
1 / g. In addition, Bell Soap 28 manufactured by Nippon Bell Co., Ltd. was used for the measurement of the void amount. Further, it was found from the diffraction pattern of X-ray diffraction that the crystallinity was excellent. Further, according to a chemical analysis, the component ratio is Ti45.
6 wt%, Li 5.37 wt%, NH ₄ <0.01 wt%, Cl <0.005 wt%, and its composition is estimated to be Li _1.33 Ti _1.67 O ₄ · H ₂ O from the weight loss due to heat treatment. To be done. Furthermore, according to the DSC analysis, the adhered water was desorbed at 75 ° C and the crystal water was released at 215 ° C to give Li _1.33 T.
It was found to undergo a phase transition to i _1.67 O ₄ and crystallize at 337 ° C.

Example 2 (1) Synthesis of Titanic Acid Compound A titanic acid compound was obtained according to the method described in (1) of Example 1 above. (2) Synthesis of lithium titanate hydrate The titanate compound obtained in (1) above is repulped to give T
A slurry having an iO ₂ concentration of 56.24 g / l was obtained. 1.494 l of this slurry and 0.208 l of pure water were charged into a 3 l 4-neck flask, and an ice-cooled 3.075N lithium hydroxide aqueous solution was added over 1 hour while cooling the ice so that the temperature of the slurry was 10 to 15 ° C. Then, 0.376 l of pure water was added, and the mixture was stirred for 1 hour and aged. Next, the slurry thus obtained was charged into an autoclave and subjected to a hydrothermal treatment at a temperature of 170 ° C. for 4 hours. Next, the hydrothermally treated slurry was filtered and then dried at a temperature of 110 ° C. without washing to obtain a lithium titanate hydrate of the present invention (Sample B).

The physical properties of the sample B thus obtained were examined. As a result, this lithium titanate hydrate had a major axis of 0.8 μm and a minor axis of 0.65 as observed by an electron microscope.
It was found to have an extremely thin plate-like shape with a thickness of about 20 μm and a thickness of about 20 nm. The specific surface area was 119.2 m ² / g and the void volume was 0.408 ml / g. In addition, Bell Soap 28 manufactured by Nippon Bell Co., Ltd. was used for the measurement of the void amount. Further, it was found from the diffraction pattern of X-ray diffraction that the crystallinity was excellent. Furthermore, according to the chemical analysis, the component ratios are as follows: Ti 43.1 wt%, Li 4.85 wt%, NH ₄ <0.01 wt%, Cl <0.005 wt%
The existence of Li _1.33 Ti _1.67 O _{4 .H 2} O was confirmed by X-ray diffraction. Furthermore, according to DSC analysis, 20
It was found that the water of crystallization was released at 8 ° C. to cause a phase transition to Li _1.33 Ti _1.67 O ₄ and crystallized at 345 ° C.

Example 3 Lithium titanate hydrate (Sample C) of the present invention was obtained by the same procedure as in Example 2 except that the hydrothermal treatment temperature was 150 ° C.

The physical properties of the sample C thus obtained were examined. As a result, this lithium titanate hydrate had a major axis of 0.8 μm and a minor axis of 0.65 as observed by an electron microscope.
It was found to have an extremely thin plate-like shape with a thickness of about 20 μm and a thickness of about 20 nm. The specific surface area was 130.1 m ² / g, and the void volume was 0.327 ml / g. In addition, Bell Soap 28 manufactured by Nippon Bell Co., Ltd. was used for the measurement of the void amount. Further, it was found from the diffraction pattern of X-ray diffraction that the crystallinity was excellent. Furthermore, according to the chemical analysis, the component ratios are as follows: Ti 43.2 wt%, Li 4.80 wt%, NH ₄ <0.01 wt%, Cl <0.005 wt%
The existence of Li _1.33 Ti _1.67 O _{4 .H 2} O was confirmed by X-ray diffraction. Furthermore, according to DSC analysis, 20
It was found that the water of crystallization was released at 6 ° C. to _{undergo a} phase transition to Li _1.33 Ti _1.67 O ₄ and crystallized at 355 ° C.

Example 4 (1) Synthesis of Titanic Acid Compound A titanic acid compound was obtained according to the method described in (1) of Example 1 above. (2) Synthesis of lithium titanate hydrate The titanate compound obtained in (1) above is repulped to give T
A slurry having an iO ₂ concentration of 55.02 g / l was obtained. The pH of this slurry was 6.90 and the conductivity was 330 μS /
cm. 3.64 l of this slurry was charged into a 5-l4 neck flask, and while cooling the ice with ice so that the temperature of the slurry was 10 to 15 ° C, an aqueous solution in which 84.97 g of lithium hydroxide monohydrate was dissolved in 360 ml of pure water was added. It was added over time and then aged for 1 hour. After completion of the addition, the pH of the slurry was 12.1, and the TiO ₂ concentration was 50 g / l. The added lithium compound is Li / Ti
The molar ratio was 0.8. Next, the slurry thus obtained was heated to 95 ° C. and reacted at that temperature for 2 hours. The reaction slurry obtained is then cooled, then filtered and then dried without washing at a temperature of 50 ° C.,
A lithium titanate hydrate of the present invention (Sample D) was obtained.

The physical properties of the sample D thus obtained were examined. As a result, it was found by electron microscope observation that the lithium titanate hydrate was an aggregate of fine particles of about 300 nm and had an extremely thin plate shape. The specific surface area is 6.2 m ² / g and the void volume is 0.016 m
1 / g. Moreover, according to the chemical analysis, the component ratios thereof are: Ti 44.1 wt%, Li 4.61 wt%, NH
₄ 0.02% by weight, Cl <0.005% by weight, X
The presence of Li _1.33 Ti _1.67 O _{4 .H 2} O was confirmed by line diffraction. Furthermore, according to DSC analysis, Li at 348 ° C.
It was found to undergo a phase transition to _1.33 Ti _1.67 O ₄ and crystallize at 476 ° C.

Example 5 In Example 2, after adding an aqueous solution of lithium hydroxide over 1 hour, 0.138 of an aqueous solution of ammonia of 0.138 was added.
1 and pure water 0.238 l were added and treated in the same manner as in Example 2 except that the mixture was stirred for 1 hour for aging to obtain a lithium titanate hydrate of the present invention (Sample E). The concentration of the ammonium compound during the hydrothermal treatment is 0.5 mol / l.

The physical properties of the sample E thus obtained were examined. As a result, this lithium titanate hydrate had a major axis of 0.8 μm and a minor axis of 0.65 as observed by an electron microscope.
It was found to have an extremely thin plate-like shape with a thickness of about 20 μm and a thickness of about 20 nm. The specific surface area was 126.9 m ² / g and the void volume was 0.389 ml / g. In addition, Bell Soap 28 manufactured by Nippon Bell Co., Ltd. was used for the measurement of the void amount. Further, it was found from the diffraction pattern of X-ray diffraction that the crystallinity was excellent. Further, according to the chemical analysis, the component ratios thereof are Ti 43.0% by weight, Li 4.83% by weight, NH ₄ 0.05% by weight, Cl <0.005% by weight, and from X-ray diffraction, it is Li _1.33 Ti _1.67. The presence of O ₄ · H ₂ O was confirmed. Furthermore, according to the DSC analysis, 208
It was found that the water of crystallization was released at 0 ° C. to _{undergo a} phase transition to Li _1.33 Ti _1.67 O ₄ and crystallized at 344 ° C.

Example 6 In Example 2, after adding an aqueous lithium hydroxide solution over 1 hour, 0.276 aqueous ammonia solution of 8.71N
Lithium titanate hydrate (Sample F) of the present invention was obtained by the same treatment as in Example 2 except that 1 l of pure water and 0.1 l of pure water were added and the mixture was stirred for 1 hour for aging. The concentration of the ammonium compound during the hydrothermal treatment is 1.0 mol / l.

The physical properties of the sample F thus obtained were examined. As a result, this lithium titanate hydrate had a major axis of 0.8 μm and a minor axis of 0.65 as observed by an electron microscope.
It was found to have an extremely thin plate-like shape with a thickness of about 20 μm and a thickness of about 20 nm. The specific surface area was 113.9 m ² / g, and the void volume was 0.559 ml / g. In addition, Bell Soap 28 manufactured by Nippon Bell Co., Ltd. was used for the measurement of the void amount. Further, it was found from the diffraction pattern of X-ray diffraction that the crystallinity was excellent. Further, according to the chemical analysis, the component ratios thereof are Ti 42.7% by weight, Li 4.97% by weight, NH ₄ 0.05% by weight, Cl <0.005% by weight, and from the X-ray diffraction, it is Li _1.33 Ti _1.67. The presence of O ₄ · H ₂ O was confirmed. Furthermore, according to the DSC analysis, 209
It was found that the water of crystallization was released at 0 ° C. to _{undergo a} phase transition to Li _1.33 Ti _1.67 O ₄ and crystallized at 334 ° C.

Samples E and F obtained in the presence of an ammonium compound during hydrothermal treatment (Examples 5 and 6) and samples A and B obtained in the absence of an ammonium compound (Examples 1 and 2) Comparing with, it was found that Samples E and F in which the ammonium compound was present had a larger amount of voids, and at the same hydrothermal treatment temperature, a well-shaped lithium titanate hydrate with good crystallinity was obtained. It was

As a result of heat-treating the samples A to F obtained in Examples 1 to 6 at a temperature of 250 to 1300 ° C., it was confirmed that lithium titanate was obtained.

[0031]

INDUSTRIAL APPLICABILITY The present invention is a lithium titanate hydrate having a flaky or plate-like particle shape, and lithium titanate having excellent properties can be obtained. Further, the lithium titanate hydrate of the present invention is a useful compound that can be used in various applications such as an ultraviolet absorber because the size and shape of particles are controlled.

The present invention further comprises a step of reacting a titanium compound and an ammonium compound in water to obtain a titanate compound, and a step of reacting the titanate compound and a lithium compound in water. A method for producing a lithium acid hydrate, which is a method capable of efficiently obtaining the above lithium titanate hydrate.

[Brief description of drawings]

FIG. 1 is an electron micrograph showing the particle shape of the lithium titanate hydrate obtained in Example 1.

2 is an X-ray diffraction pattern of the lithium titanate hydrate obtained in Example 1. FIG.

3 is a DSC analysis pattern of the lithium titanate hydrate obtained in Example 1. FIG.

4 is an electron micrograph showing the particle shape of the lithium titanate hydrate obtained in Example 4. FIG.

5 is an X-ray diffraction pattern of the lithium titanate hydrate obtained in Example 4. FIG.

6 is a DSC analysis pattern of the lithium titanate hydrate obtained in Example 4. FIG.

Claims (7)

[Claims] 1. A lithium titanate hydrate having a flaky or plate-like particle shape. 2. The lithium titanate hydrate according to claim 1, which has a laminated structure. 3. The lithium titanate hydrate according to claim 1, which has a specific surface area in the range of 1 to 300 m ² / g. 4. The lithium titanate hydrate according to claim 1, which has a longest particle size in the range of 0.1 to 50 μm. 5. Lithium titanate hydrate comprising the steps of reacting a titanium compound with an ammonium compound in water to obtain a titanate compound, and reacting the titanate compound with a lithium compound in water. Method of manufacturing things. 6. The method for producing a lithium titanate hydrate according to claim 5, wherein the titanate compound and the lithium compound are hydrothermally treated in water. 7. The method for producing a lithium titanate hydrate according to claim 6, wherein the hydrothermal treatment is performed in the presence of an ammonium compound.