CN110272067B - Preparation method of hydrated layered nano lithium titanate - Google Patents

Abstract

The invention discloses a preparation method of hydrated layered nano lithium titanate, which comprises the following stepsThe method comprises the following steps: (1) preparing a lithium source water solution; (2) mixing a titanium source precursor with ethanol, adding deionized water, continuously stirring to obtain a precipitate, and washing to obtain a solid substance; (3) mixing the solid matter prepared in the step (2) with the lithium source aqueous solution prepared in the step (1), and performing hydrothermal reaction and post-treatment to obtain the hydrated layered nano lithium titanate; the hydrated layered nano lithium titanate has a structural formula of Li_1.81H_0.19Ti₂O₅·2H₂And O. The preparation method disclosed by the invention can be used for preparing the hydrated layered nano lithium titanate with uniform appearance, excellent dispersion performance and pure phase, and is beneficial to further synthesizing the spinel type lithium titanate with good dispersion.

Description

Preparation method of hydrated layered nano lithium titanate

Technical Field

The invention relates to the technical field of inorganic materials, in particular to a preparation method of hydrated layered nano lithium titanate.

Background

With the increasing weight of energy and environmental problems, the development of novel green energy becomes the key point of current scientific research personnel. The lithium ion battery has the advantages of long service life, high temperature resistance, large capacity, no memory effect and the like, and is widely applied to the fields of electronic equipment, electric automobiles and the like. Spinel type lithium titanate (Li)₄Ti₅O₁₂) The lithium ion battery cathode material has the advantages of zero strain in the lithium ion intercalation/deintercalation process, high electrode potential (1.55V vs Li +/Li), difficulty in generating an SEI film, good safety, low cost and the like, and therefore, the lithium ion battery cathode material becomes the research focus of the current lithium ion battery cathode material.

Liquid phase methods, such as sol-gel methods, hydrothermal methods, are currently common methods for synthesizing lithium titanate. However, it is difficult to synthesize spinel-type lithium titanate (Li) by liquid phase method in one step₄Ti₅O₁₂) Instead, water and a layered lithium titanate (Li) are first obtained_1.81H_0.19Ti₂O₅·2H₂O), and then calcining the crystal form at high temperature to complete crystal form transformation. Therefore, in order to better control the morphology of spinel-type lithium titanate, the precursor (Li)_1.81H_0.19Ti₂O₅·2H₂O) is particularly important. However, the current liquid phase synthesis method usually adopts ethanolThe product obtained by the solvothermal method using water as a solvent has poor dispersibility, and the microspheres are formed by overlapping the sheets layer by layer and have uneven appearance.

Therefore, there is a need to propose a new solution to the above problems.

Disclosure of Invention

Aiming at the technical problems in the prior art, the invention discloses a preparation method of hydrated layered nano lithium titanate, which can be used for preparing the hydrated layered nano lithium titanate with uniform appearance, excellent dispersion performance and pure phase, and is beneficial to further synthesizing spinel type lithium titanate with good dispersibility.

The specific technical scheme is as follows:

a preparation method of hydrated layered nano lithium titanate comprises the following steps:

(1) preparing a lithium source water solution;

(2) mixing a titanium source precursor with ethanol, adding deionized water, continuously stirring to obtain a precipitate, and washing to obtain a solid substance;

(3) mixing the solid matter prepared in the step (2) with the lithium source aqueous solution prepared in the step (1), and performing hydrothermal reaction and post-treatment to obtain the hydrated layered nano lithium titanate;

the structural formula of the hydrated layered nano lithium titanate is Li_1.81H_0.19Ti₂O₅·2H₂O。

In order to avoid the problems of impure product phases, poor dispersibility and the like caused by the introduction of an ethanol solvent, the invention firstly proposes that a titanium source precursor is added into a mixed system of ethanol and water to generate a precipitate, and the obtained white precipitate is a titanium source which is mixed with an aqueous solution of a lithium source in a solid form and then subjected to hydrothermal reaction. The product obtained by the method has uniform appearance and good dispersibility in water and ethanol.

The invention completely avoids introducing ethanol in the hydrothermal reaction through optimizing the preparation process. And further optimizing the preparation process parameters to prepare the hydrated layered nano lithium titanate with uniform appearance, excellent dispersion performance and pure phase (without impurity phase).

However, through a comparative experiment, it is found that if the preparation process in the prior art is adopted under the same preparation process parameters, although the heterogeneous hydrated layered nano lithium titanate can be obtained through the optimization of the process parameters, the morphology of the hydrated layered nano lithium titanate in the product is not uniform, the dispersibility is poor, and the further synthesis of the spinel type lithium titanate with good dispersibility is not facilitated. It has also been found that the preparation process is more sensitive to variations in the concentration of the lithium source, and that the prior art preparation process has a smaller adjustment range of the lithium source than the preparation process of the present invention, beyond which significant impurities in the product occur, and are therefore more detrimental to the actual production.

In the step (1):

the lithium source is selected from lithium hydroxide or lithium hydroxide monohydrate;

preferably, the concentration of the lithium source water solution is 0.175-0.225 mol/L, and experiments show that the selection of the concentration of the lithium source is important for obtaining pure-phase hydrated layered nano lithium titanate. When the concentration of the lithium source aqueous solution is too low, an anatase titanium dioxide heterogeneous phase can be generated in the product; when the concentration of the lithium source aqueous solution is too high, the product is no longer hydrated layered nano lithium titanate.

In the step (2):

the titanium source precursor is selected from titanate esters, and tetrabutyl titanate is preferred.

Preferably, the volume ratio of the ethanol to the water is 1-5: 1; more preferably 2: 1.

preferably, the mass-to-volume ratio of the titanium source precursor to the ethanol is 0.1-1 mol/L; further preferably 0.5 mol/L.

In the step (3):

preferably, the mass-to-volume ratio of the solid matter to the lithium source aqueous solution is 42.5-47.5 g/L; further preferably 45 to 47.5 g/L.

Preferably, the solid substance and the lithium source aqueous solution are subjected to hydrothermal reaction after being vigorously stirred on a magnetic stirring table for 10-20 min.

Preferably, the temperature of the hydrothermal reaction is 180-200 ℃. Tests show that the hydrated layered nano lithium titanate with uniform appearance, excellent dispersion performance and pure phase can be prepared by controlling the hydrothermal reaction temperature within the optimized range besides the lithium source concentration. Experiments show that the hydrothermal reaction temperature is too low, and more small particles exist in the prepared product; the hydrothermal reaction temperature is too high, and other heterogeneous phases are generated in the product.

Preferably, the post-treatment comprises washing, drying. The drying temperature is 60-80 ℃, and the drying time is 8-12 h.

Further preferably:

the concentration of the lithium source water solution is 0.175-0.225 mol/L;

the mass-to-volume ratio of the titanium source precursor to the ethanol is 0.5mol/L, and the volume ratio of the ethanol to the water is 2: 1;

the mass-volume ratio of the solid matter to the lithium source water solution is 45-47.5 g/L;

the temperature of the hydrothermal reaction is 180-200 ℃.

Tests show that the product prepared by adopting the further optimized process parameters has uniform appearance and optimal dispersion performance, and is favorable for further synthesizing the spinel type lithium titanate with good dispersibility.

Compared with the prior art, the invention has the beneficial effects that:

according to the invention, water is used as a solvent, hydrolysis precipitation of tetrabutyl titanate is used as a titanium source, and the titanium source and a lithium source are subjected to hydrothermal reaction in an aqueous solution, so that the hydrated layered lithium titanate is successfully prepared. Compared with the traditional solvothermal method, the product prepared by the technical scheme of the invention has less impurity phase, uniform appearance and better dispersibility. Better dispersion in electrochemical systems means a larger specific surface area, a shorter free path for ion diffusion, and also leads to better electrochemical performance. Therefore, the precursor with good dispersibility synthesized by the method has important significance for synthesizing the lithium titanate electrode with excellent electrochemical performance.

Drawings

FIG. 1 is an XRD pattern of the product prepared in example 1;

FIG. 2 is an SEM photograph of a product prepared in example 1;

FIG. 3 is an XRD pattern of the product prepared in comparative example 1;

FIG. 4 is an SEM photograph of a product prepared in comparative example 1;

FIG. 5 is an XRD pattern of the product prepared in comparative example 2;

FIG. 6 is an XRD pattern of the product prepared in comparative example 3;

FIG. 7 is an XRD pattern of the product prepared in example 2;

FIG. 8 is an SEM photograph of the product of example 2 at different magnifications;

FIG. 9 is an XRD pattern of the product prepared in comparative example 4;

FIG. 10 is an SEM photograph of a product prepared in comparative example 4;

FIG. 11 is an XRD pattern of a product prepared in comparative example 5;

FIG. 12 is an SEM photograph of a product prepared in comparative example 5;

fig. 13 is an XRD pattern of the product prepared in comparative example 6.

Detailed Description

The present invention will be described in further detail with reference to examples, but the embodiments of the present invention are not limited thereto.

Example 1

(1) 7mmol of lithium hydroxide monohydrate was added to 40mL of deionized water with stirring to form a solution.

(2) 1.7mL (5mmol) of tetrabutyl titanate is dripped into 10mL of ethanol by a pipette, and then 5mL of deionized water is immediately dripped into the ethanol solution to form a white precipitate and the mixture is continuously stirred; the precipitate was washed twice with deionized water by centrifugation (8000 rpm).

(3) Adding 1.8g of precipitate into an aqueous solution of lithium hydroxide monohydrate, stirring strongly for 10min, pouring the stirred mixture into a 50mL polytetrafluoroethylene reaction kettle, and reacting at 180 ℃ for 36 h; after the reaction is finished, the product is respectively centrifugally washed for three times by deionized water and ethanol, and dried for 12 hours at 80 ℃ to obtain the final product.

FIG. 1 is an XRD pattern of the product prepared in this example, and it can be confirmed from FIG. 1 that the product isIs Li_1.81H_0.19Ti₂O₅·2H₂O, the product has pure phase and no impurity phase.

Fig. 2 is an SEM photograph of the product prepared in this example, and it can be seen from fig. 2 that the product is in the shape of nano-sheet, regular and uniform in morphology, and good in dispersibility.

Comparative example 1

The preparation process in the prior art is adopted, and specifically comprises the following steps:

(1) 7mmol of lithium hydroxide monohydrate was dissolved in 20mL of deionized water with stirring to form a solution.

(2) 1.7mL of tetrabutyl titanate was added to 20mL of ethanol, and the ethanol solution of tetrabutyl titanate was added to the aqueous solution of lithium hydroxide monohydrate with vigorous stirring and stirring was continued for 2 hours to obtain a mixed solution.

(3) The mixed solution is added into a 50mL reaction kettle and reacted for 36h at a constant temperature of 180 ℃. After the reaction is finished, the product is respectively centrifugally washed for three times by deionized water and ethanol, and dried for 12 hours at 80 ℃ to obtain the product.

FIG. 3 is an XRD pattern of the product of this comparative example, from which it can be seen that the product is phase-pure Li_1.81H_0.19Ti₂O₅·2H₂O。

FIG. 4 is an SEM photograph of a product prepared by the comparative example, and the observation shows that the product has insufficient uniformity in appearance and size and poor dispersibility.

Comparative example 2

The preparation process was exactly the same as in example 1 except that the amount of lithium hydroxide monohydrate added in step (1) was adjusted to 4mmol, and the process parameters in the other steps were exactly the same.

FIG. 5 is an XRD pattern of a product prepared in this comparative example, and it was observed that anatase TiO form was present in the product₂The miscellaneous phase of (1).

Comparative example 3

The preparation process was exactly the same as in example 1 except that the amount of lithium hydroxide monohydrate added in step (1) was adjusted to 12mmol, and the process parameters in the other steps were exactly the same.

FIG. 6 shows the product of this comparative exampleThe XRD pattern of the product is observed, and the product is LiTiO₂And Li was not observed_1.81H_0.19Ti₂O₅·2H₂Characteristic peak of O.

Example 2

(1) 9mmol of lithium hydroxide monohydrate was added to 40mL of deionized water with stirring to form a solution.

(2) 1.7mL of tetrabutyl titanate is dripped into 10mL of ethanol by a liquid transfer gun, and then 5mL of deionized water is dripped into the ethanol solution immediately to form white precipitate and the mixture is continuously stirred; the precipitate was washed twice with deionized water by centrifugation (8000 rpm).

(3) Adding 1.9g of precipitate into an aqueous solution of lithium hydroxide monohydrate, stirring strongly for 10min, pouring the stirred mixture into a 50mL polytetrafluoroethylene reaction kettle, and reacting at 200 ℃ for 36 h; after the reaction is finished, the product is respectively centrifugally washed for three times by deionized water and ethanol, and is dried for 12 hours at the temperature of 80 ℃ to obtain the final product.

FIG. 7 is an XRD pattern of the product of this example, which was observed to be Li_1.81H_0.19Ti₂O₅·2H₂And O, the product phase is pure and has no impurity phase.

FIG. 8 is an SEM photograph of the product prepared in this example at different magnifications, and the observation shows that the product is in a nano-sheet shape and has better dispersibility; from the magnified SEM photograph (b), it can be seen that the surface of the product is smooth and flat, and the lamellar structure is completely retained.

Comparative example 4

The preparation process in the prior art is adopted, and specifically comprises the following steps:

(1) 9mmol of lithium hydroxide monohydrate was dissolved in 20mL of deionized water with stirring to form a solution.

(2) 1.7mL of tetrabutyl titanate was added to 20mL of ethanol, and the ethanol solution of tetrabutyl titanate was added to the aqueous solution of lithium hydroxide monohydrate with vigorous stirring and stirring was continued for 2 hours to obtain a mixed solution.

(3) The mixed solution is added into a 50mL reaction kettle and reacted for 36h at the constant temperature of 200 ℃. After the reaction is finished, the product is respectively centrifugally washed for three times by deionized water and ethanol, and dried for 12 hours at 80 ℃ to obtain the product.

FIG. 9 is an XRD pattern of a product prepared in this comparative example, and it was observed that the product was LiTiO₂。

FIG. 10 is an SEM photograph of a product of this comparative example, which was observed to be a pile of small particles.

Comparative example 5

The preparation process was identical to that of example 2 except that the hydrothermal reaction temperature in step (3) was adjusted to 160 deg.C and the process parameters in the other steps were identical.

FIG. 11 is an XRD pattern of a product prepared in this comparative example, and it was observed that the product was Li_1.81H_0.19Ti₂O₅·2H₂O。

Fig. 12 is an SEM photograph of the product prepared by the comparative example, and the observation shows that the surface of the nanosheet in the product is rough, and there are many small particles, which may be because the growth rate of the nanosheet is slowed down by the lower reaction temperature, so that some small particles do not grow into the sheet.

Comparative example 6

The preparation process was identical to that of example 2 except that the hydrothermal reaction temperature in step (3) was adjusted to 220 deg.C and the process parameters in the other steps were identical.

FIG. 13 is an XRD pattern of a product prepared in this comparative example, and it was observed that Li was a main phase in the product_1.81H_0.19Ti₂O₅·2H₂O, but with a small amount of LiTiO₂The presence of a heterogeneous phase.

Claims (3)

1. A preparation method of hydrated layered nano lithium titanate is characterized by comprising the following steps:

(1) preparing a lithium source water solution;

the lithium source is selected from lithium hydroxide or lithium hydroxide monohydrate;

the concentration of the lithium source water solution is 0.175-0.225 mol/L;

(2) mixing a titanium source precursor with ethanol, adding deionized water, continuously stirring to obtain a precipitate, and washing to obtain a solid substance;

the titanium source precursor is selected from tetrabutyl titanate;

the volume ratio of the ethanol to the deionized water is 1-5: 1;

the mass-to-volume ratio of the titanium source precursor to the ethanol is 0.1-1 mol/L;

(3) mixing the solid matter prepared in the step (2) with the lithium source aqueous solution prepared in the step (1), and performing hydrothermal reaction and post-treatment to obtain the hydrated layered nano lithium titanate;

the temperature of the hydrothermal reaction is 180-200 ℃;

the mass-volume ratio of the solid matter to the lithium source water solution is 42.5-47.5 g/L;

the structural formula of the hydrated layered nano lithium titanate is Li_1.81H_0.19Ti₂O₅·2H₂O。

2. The method for preparing hydrated layered nano lithium titanate according to claim 1, wherein in the step (3), the post-treatment comprises washing and drying.

3. The method for preparing hydrated layered nano lithium titanate according to claim 1, wherein:

the concentration of the lithium source water solution is 0.175-0.225 mol/L;

the mass-to-volume ratio of the titanium source precursor to the ethanol is 0.5mol/L, and the volume ratio of the ethanol to the water is 2: 1;

the mass-volume ratio of the solid matter to the lithium source water solution is 45-47.5 g/L;

the temperature of the hydrothermal reaction is 180-200 ℃.

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