CN108975390B

CN108975390B - Linear hierarchical structure lithium titanate and preparation method and application thereof

Info

Publication number: CN108975390B
Application number: CN201811037289.9A
Authority: CN
Inventors: 李建明; 金旭; 王晓琦; 焦航; 刘晓丹; 孙亮; 苏玲
Original assignee: Petrochina Co Ltd
Current assignee: Petrochina Co Ltd
Priority date: 2018-09-06
Filing date: 2018-09-06
Publication date: 2021-01-29
Anticipated expiration: 2038-09-06
Also published as: CN108975390A

Abstract

The invention provides lithium titanate with a linear hierarchical structure, and a preparation method and application thereof. The method comprises the following steps: (S1) dispersing a titanium source in an aqueous hydrogen peroxide solution containing lithium hydroxide to obtain a transparent solution; (S2) heating the transparent solution obtained in the step (S1) to react to obtain a precursor with a linear structure; (S3) separating the linear structure precursor obtained in the step (S2) and drying the precursor; (S4) hydrothermally reacting the linear structure precursor dried in step (S3) to obtain the linear hierarchical structure lithium titanate. The obtained linear hierarchical structure lithium titanate long shaft is beneficial to effective migration of electrons, the hierarchical structure is beneficial to the rapid embedding and embedding processes of lithium ions, sodium ions or potassium ions, the large specific surface area is beneficial to the contact area of electrolyte and an electrode, the current density is reduced, and the battery has good rapid charge and discharge performance.

Description

Linear hierarchical structure lithium titanate and preparation method and application thereof

Technical Field

The invention relates to the field of materials, in particular to lithium titanate with a linear hierarchical structure, and a preparation method and application thereof.

Background

Lithium titanate, titanic acid and titanium dioxide have been widely used in the fields of lithium ion batteries, potassium ion batteries, sodium ion batteries, catalysis, photocatalysis, solar cells, photolysis of water, sensing, biology and the like, and are hot spots for research in the field of materials.

The application properties of lithium titanate, titanic acid and titanium dioxide materials are closely related to the morphological structure of the materials. Compared with single crystal nano particles, the one-dimensional linear nano material can reduce grain boundaries among particles, is favorable for transporting current carriers in the long axis direction, and has the following characteristics: (1) under the nanometer scale, the specific surface area and active sites of the material can be increased rapidly, and the surface reaction and the interaction with the medium can be greatly accelerated; (2) in the field of photocatalysis, photoproduction electron-hole pairs can be moved freely in the long axis direction, the recombination probability of electron holes is reduced, and the photocatalysis efficiency is improved; (3) in the field of battery electrode materials, the long axis is beneficial to effective migration of electrons, the short axis is beneficial to the rapid embedding and embedding processes of lithium, sodium or potassium ions, and compared with nanoparticles, the one-dimensional nanostructure has better charge and discharge performance; (4) in the field of solar cells, the one-dimensional nano structure can greatly reduce grain boundaries among particles, is favorable for the transmission of electrons on a photo anode, greatly improves the electron collection and conversion efficiency of the cell, and the like.

Since the hierarchical structure has a high degree of order, it can realize various functions, and its design and development are receiving attention gradually. The hierarchical structure can increase the specific surface area of the material, increase the contact orderliness of the nanoparticles, promote the effective migration of electrons and the like. However, the lithium titanate, the titanic acid and the titanium dioxide hierarchical structures reported at present are all granular, and the hierarchical structure material with a one-dimensional structure cannot be realized, so that the effective separation and transportation of electrons by the hierarchical structure material cannot be further improved.

Therefore, the preparation of the one-dimensional nano material with the hierarchical structure can greatly improve the specific surface area of the material, well reduce the grain boundary among particles, solve the problem that the electron-hole is easy to compound and improve the effective transportation of electrons in the long axis direction.

Disclosure of Invention

An object of the present invention is to provide a method for preparing lithium titanate having a linear hierarchical structure;

the invention also aims to provide the lithium titanate with the linear hierarchical structure prepared by the preparation method;

it is still another object of the present invention to provide an electrode material for an ion battery;

still another object of the present invention is to provide a method for preparing titanic acid having a linear hierarchical structure;

still another object of the present invention is to provide a linear hierarchical structure titanic acid prepared by the method;

it is still another object of the present invention to provide the use of linear hierarchical titanic acid;

still another object of the present invention is to provide a method for preparing titanium dioxide having a linear hierarchical structure;

it is still another object of the present invention to provide a linear hierarchical structure titanium dioxide.

The invention also aims to provide application of the titanium dioxide with the linear hierarchical structure.

In order to achieve the above object, in one aspect, the present invention provides a method for preparing lithium titanate, wherein the method comprises:

(S1) dispersing a titanium source in an aqueous hydrogen peroxide solution containing lithium hydroxide to obtain a transparent solution;

(S2) heating the transparent solution obtained in the step (S1) to react to obtain a precursor with a linear structure;

(S3) separating the linear structure precursor obtained in the step (S2) and drying the precursor;

(S4) hydrothermally reacting the linear structure precursor dried in step (S3) to obtain the linear hierarchical structure lithium titanate.

According to some embodiments of the invention, wherein the molar ratio of hydrogen peroxide in the aqueous hydrogen peroxide solution to the titanium source is greater than or equal to 3: 1.

according to some embodiments of the invention, wherein the molar ratio of hydrogen peroxide in the aqueous hydrogen peroxide solution to the titanium source is (4-6): 1.

according to some embodiments of the present invention, the step (S4) further includes annealing the hydrothermal reaction product to obtain the linear-shaped lithium titanate with a hierarchical structure.

According to some embodiments of the present invention, wherein the annealing treatment of the step (S4) has a temperature of 300 ℃ to 700 ℃; the time of the annealing treatment is 1h to 24 h.

According to some embodiments of the invention, the titanium source is selected from the group consisting of hydrous titanic acid, titanium ethoxide, titanium isopropoxide, titanium propoxide, tetrabutyl titanate, titanium ethoxide, titanium propoxide, titanium sulfate, titanyl sulfate, titanium tetrachloride, titanium tetrafluoride, ammonium fluotitanate, titanium nitride, titanium dioxide, metatitanic acid, and orthotitanic acid.

According to some embodiments of the invention, the titanium source is hydrous titanic acid obtained by hydrolysis of a titanium-containing compound.

According to some embodiments of the invention, the titanium-containing compound is selected from the group consisting of titanium ethoxide, titanium isopropoxide, titanium propoxide, tetrabutyl titanate, titanium ethoxide, titanium propoxide, titanium sulfate, titanium oxysulfate, titanium tetrachloride, titanium tetrafluoride, ammonium fluorotitanate, and industrial titanium-containing compounds.

According to some embodiments of the present invention, the hydrolysis reaction is a direct hydrolysis of the titanium-containing compound dispersed in water to obtain hydrous titanic acid, or the hydrolysis reaction is a direct hydrolysis of the titanium-containing compound dispersed in an aqueous solution containing an alkaline substance to obtain hydrous titanic acid.

According to some embodiments of the invention, the alkaline material is selected from the group consisting of ammonia, sodium hydroxide, potassium hydroxide, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, ethylenediamine, diethylamine, triethylamine, ethylamine, ethanolamine, and diethanolamine.

According to some embodiments of the invention, the hydrolysis reaction is performed at normal temperature and pressure.

According to some embodiments of the present invention, the titanium-containing compound is further purified after the hydrolysis reaction to obtain the hydrous titanic acid.

According to some embodiments of the present invention, the purity of the purified hydrous titanic acid is 97% or higher.

According to some embodiments of the invention, wherein the purification is selected from the group consisting of water washing-centrifugation, water washing-membrane separation, water washing-filtration and dialysis.

According to some embodiments of the present invention, wherein the concentration of lithium hydroxide in the aqueous solution of hydrogen peroxide containing lithium hydroxide in step (S1) is 0.4mol/L to 1.0 mol/L.

According to some embodiments of the invention, the volume fraction of hydrogen peroxide in the aqueous hydrogen peroxide solution containing lithium hydroxide is between 0.5% and 10%.

According to some embodiments of the present invention, wherein the heating to perform the reaction in the step (S2) is heating to 60 ℃ to 100 ℃ to perform the reaction.

According to some embodiments of the present invention, the heating in step (S2) is performed by heating to 60 ℃ to 100 ℃ for 0.5h to 24 h.

According to some embodiments of the present invention, the heating in step (S2) is performed by heating to 60 ℃ to 100 ℃ for 3h to 10 h.

According to some embodiments of the present invention, the separation method of the line-like structure precursor obtained in the step (S3) (S2) is selected from one or more of centrifugation, suction filtration, and membrane separation.

According to some embodiments of the present invention, wherein the temperature of the drying in the step (S3) is 20 ℃ to 80 ℃.

According to some embodiments of the invention, wherein the drying is selected from the group consisting of low temperature drying and/or vacuum drying.

According to some embodiments of the invention, wherein the hydrothermal reaction in step (S4) has a reaction temperature of 80 ℃ to 150 ℃.

According to some embodiments of the invention, wherein the hydrothermal reaction in step (S4) has a reaction temperature of 100 ℃ to 150 ℃.

According to some embodiments of the invention, wherein the hydrothermal reaction time in step (S4) is 1h to 24 h.

According to some embodiments of the invention, wherein the hydrothermal reaction time in step (S4) is 1h to 8 h.

According to some embodiments of the present invention, the method further comprises a step of performing surface modification on the obtained linear-shaped lithium titanate in step (S4) after hydrothermal reaction to obtain the linear-shaped lithium titanate in step (S4).

According to some embodiments of the present invention, the surface modification is to load a combination of one or more selected from carbon, carbon nanotubes, graphene, black phosphorus, and metal on the surface of the linear hierarchical structure lithium titanate.

On the other hand, the invention also provides the lithium titanate with the linear hierarchical structure prepared by the preparation method.

In another aspect, the invention further provides an electrode material of an ion battery, wherein a preparation raw material of the electrode material comprises the linear hierarchical structure lithium titanate.

According to some embodiments of the invention, the ion battery is a lithium ion battery, a sodium ion battery, a potassium ion battery or a magnesium ion battery.

In another aspect, the invention further provides a preparation method of the linear hierarchical structure titanic acid, wherein the method comprises the step of performing acid exchange on the linear hierarchical structure lithium titanate to obtain the linear hierarchical structure titanic acid.

According to some embodiments of the present invention, the acid exchange includes placing the nanoscale hierarchical structure lithium titanate into an acid solution to perform hydrogen ion exchange, so as to obtain the linear hierarchical structure titanic acid, wherein the acid concentration in the acid solution is 0.01mol/L-0.1 mol/L.

According to some embodiments of the invention, the acid is selected from the group consisting of nitric acid, hydrochloric acid, sulfuric acid and acetic acid.

According to some embodiments of the present invention, the method further comprises a step of washing the linear graded-structure titanic acid before the acid exchange, and then subjecting the washed linear graded-structure titanic acid to an acid exchange treatment, and then washing and drying the linear graded-structure titanic acid obtained by the acid exchange treatment.

In another aspect, the invention also provides the linear hierarchical structure titanic acid prepared by the method.

In another aspect, the invention also provides the application of the linear hierarchical structure titanic acid in preparing ion batteries or pollutant adsorption.

In another aspect, the present invention also provides a method for preparing titanium dioxide with a linear hierarchical structure, wherein the method comprises subjecting the titanic acid with a linear hierarchical structure of the present invention to a hydrothermal reaction and/or an annealing treatment to obtain the titanium dioxide with a linear hierarchical structure.

According to some embodiments of the present invention, the reaction system of the hydrothermal reaction is a neutral water system, an acidic water system or a basic water system; the temperature of the hydrothermal reaction is 100-200 ℃.

According to some embodiments of the invention, the hydrothermal reaction time is 1-24 h.

According to some embodiments of the invention, the hydrothermal reaction time is 5h to 24 h.

According to some embodiments of the invention, the temperature of the annealing treatment is 350 ℃ to 800 ℃.

According to some embodiments of the invention, the temperature of the annealing treatment is 400 ℃ to 600 ℃.

According to some embodiments of the invention, the annealing is performed for a period of time ranging from 1 hour to 24 hours.

According to some embodiments of the invention, the annealing is performed for a time period of 3h to 5 h.

In another aspect, the invention also provides the titanium dioxide with the linear hierarchical structure prepared by the preparation method.

In still another aspect, the invention also provides the application of the linear hierarchical structure titanium dioxide in the fields of photocatalytic degradation of organic pollutants, biomedicine and preparation of hydrogenation catalysts, dye-sensitized solar cells, perovskite solar cells, hydrophilic materials and hydrophobic materials.

It should be emphasized that the term "comprises/comprising" when used herein, is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps or components.

In conclusion, the invention provides a lithium titanate with a linear hierarchical structure, and a preparation method and application thereof. The technical scheme of the invention has the following advantages:

(1) the long shaft of the hierarchical structure is beneficial to effective migration of electrons, the hierarchical structure is beneficial to the rapid embedding and embedding processes of lithium ions, sodium ions or potassium ions, the large specific surface area is beneficial to the contact area of electrolyte and an electrode, the current density is reduced, and the battery has good rapid charge and discharge performance.

(2) The hierarchical structure is beneficial to electron-hole separation, increases catalytic reaction active sites, has higher photocatalytic activity, and is beneficial to hydrogen production by photolysis or photocatalytic degradation of organic pollutants.

(3) The larger specific surface area of the hierarchical structure can adsorb more dyes, and the one-dimensional structure is favorable for the transmission of electrons and has advantages in the aspect of solar cells.

(4) The hierarchical structure is beneficial to gas sensing, such as the sensing of gases such as hydrogen, oxygen, formaldehyde, propane, ethane, methane, carbon monoxide, carbon dioxide, water vapor and the like.

(5) The hierarchical structure has a large specific surface area, can adsorb more organic matters or heavy metal ions, plays a role in environmental management, has large mass and volume due to the fact that a single hierarchical structure is linear, is easy to perform self-settling separation or membrane separation, and improves the repeated recycling effect of materials.

Drawings

FIG. 1 is a flow chart of the preparation of the present invention;

fig. 2 is a high-low SEM topography of the linear hierarchical structure lithium titanate material obtained in example 1;

fig. 3 is a discharge capacity diagram of the lithium ion battery with different charge and discharge rates, in which the linear hierarchical structure lithium titanate material obtained in example 1 is applied to a negative electrode of the lithium ion battery;

fig. 4 is a discharge capacity diagram of the lithium ion battery with different charge and discharge rates, in which the linear hierarchical structure lithium titanate material obtained in example 2 is applied to a negative electrode of the lithium ion battery;

FIG. 5 is a graph of the discharge capacity of the sodium-ion battery at different charge and discharge rates when the linear hierarchical structure titanic acid material obtained in example 8 is applied to the negative electrode of the sodium-ion battery;

FIG. 6 is an SEM topography of the linear hierarchical structure titania material obtained in example 11;

FIG. 7 is a graph showing the rate of photocatalytic degradation of rhodamine B in the titania material having a linear hierarchical structure obtained in example 11.

Detailed Description

The following detailed description is provided for the purpose of illustrating the embodiments and the advantageous effects thereof, and is not intended to limit the scope of the present disclosure.

Example 1

According to the flow of the figure 1, 1 g of titanyl sulfate is dispersed and dissolved in 100ml of aqueous solution under the condition of stirring to form solution, then ammonia water with the concentration of 0.05 mol per liter is slowly dripped into the solution until the solution is neutral, the titanyl sulfate is gradually and completely hydrolyzed to generate hydrous titanic acid precipitate, then the hydrous titanic acid precipitate is ultrasonically dispersed, washed by deionized water for multiple times, and centrifugally separated. Next, hydrogen peroxide and lithium hydroxide were dissolved in water to form an aqueous solution having a lithium hydroxide concentration of 0.7 mole per liter and a hydrogen peroxide volume fraction of 2.5%. Subsequently, the hydrous titanic acid precipitate after the above centrifugal separation was dispersed in 100ml of the aqueous hydrogen peroxide solution containing lithium hydroxide prepared above, and stirred to form a yellow transparent solution. Then, the above yellow transparent solution was heated to 75 ℃ and stirred at a constant temperature for 8 hours, and the reaction was stopped and separated to obtain a white solid. Subsequently, the white solid was put into an oven and dried at 60 ℃ for 20 hours. Subsequently, the above-mentioned dried white solid powder was dispersed in 100mL of pure water and reacted at 100 ℃ for 5 hours to obtain a lithium titanate product having a linear hierarchical structure.

The SEM morphology map of the linear hierarchical structure lithium titanate material obtained in this example is shown in fig. 2, where a in fig. 2 shows that the product is a linear structure, the diameter of the linear structure is 20 nm to 1 micron, the length of the linear structure is 1 micron to 50 microns, and the aspect ratio is greater than 10; as can be seen from b of fig. 2, the linear structure is a linear hierarchical structure, the surface of which is composed of nanosheet particles, the size of the nanosheets is mainly 5 nm to 100 nm, and the thickness is 1 nm to 10 nm.

The discharge capacity test results of the lithium ion battery using the lithium titanate material with the linear hierarchical structure obtained in this example as the electrode material at different charge and discharge rates are shown in fig. 3. The preparation of the lithium ion battery electrode adopts a blade coating method, and firstly, according to the lithium titanate product: super P: polyvinylidene fluoride (PVDF) is in a mass ratio of 7:2:1, N-methyl pyrrolidone (NMP) is used as a solvent to be mixed into slurry, a blade coater is used for uniformly coating the slurry on a copper foil, then metal lithium is used as a counter electrode in a glove box, and 1mol/L LiPF is adopted₆The electrochemical test was carried out on button cells of type CR2032 assembled with/EC-DMC-EMC (1:1:1) as electrolyte and Glass Fiber as separator. As can be seen in fig. 3, the material structure has the following characteristics: (1) the linear structure has a large length-diameter ratio which is mainly 10 to 100, and compared with nano particles, the linear structure can greatly reduce grain boundaries among the particles, is favorable for effective migration of electrons in the long axis direction, and improves the overall conductivity of the electrode material; (2) the thickness of the nanosheet with the flaky hierarchical structure is mainly 1-10 nanometers, and the nanosheet has a very short lithium ion migration path, so that the intercalation and deintercalation processes of lithium ions can be rapidly promoted, and the multiplying power charge and discharge performance can be promoted; (3) the hierarchical structure has a large specific surface area, which is beneficial to the contact area of the electrolyte and the electrode and reduces the current density; (4) the linear hierarchical structure is easy to be fully and uniformly mixed with the conductive agent, and the number of lines is increasedThe effective conductive contact between the two promotes the effective transportation of electrons. Therefore, the lithium titanate material with the structure has excellent charge and discharge performance of the lithium ion battery, and the average battery capacity is respectively kept at 190, 173, 164, 152, 145, 139 and 126mAhg at different charge and discharge rates of 1C, 2C, 5C, 10C, 15C, 20C and 50C^-1Is higher than other reported linear lithium titanate materials.

Example 2

According to the flow of the figure 1, under the stirring condition, 2 g of titanium sulfate is dispersed and dissolved in 100ml of aqueous solution to form solution, then sodium hydroxide with the concentration of 0.1mol per liter is slowly dripped into the solution until the solution is neutral, so that the titanium sulfate is gradually and completely hydrolyzed to generate hydrous titanic acid precipitate, then the hydrous titanic acid precipitate is ultrasonically dispersed, washed by deionized water for multiple times, and centrifugally separated. Next, hydrogen peroxide and lithium hydroxide were dissolved in water to form an aqueous solution having a lithium hydroxide concentration of 0.8 mole per liter and a hydrogen peroxide volume fraction of 4%. Subsequently, the hydrous titanic acid precipitate after the above centrifugal separation was dispersed in 100ml of the aqueous hydrogen peroxide solution containing lithium hydroxide prepared above, and stirred to form a yellow transparent solution. Then, the above yellow transparent solution was heated to 85 ℃ and stirred at a constant temperature for 6 hours, and the reaction was stopped and separated to obtain a white solid. Subsequently, the white solid was put into an oven and dried at 70 ℃ for 20 hours. Subsequently, the above-mentioned dried white solid powder was dispersed in 100mL of pure water and reacted at 120 ℃ for 4 hours to obtain a lithium titanate product having a linear hierarchical structure. And then, putting the lithium titanate with the linear hierarchical structure into a muffle furnace, and heating at 400 ℃ for 5 hours to obtain the spinel type lithium titanate material with the linear hierarchical structure. The morphology map of the lithium titanate material with the linear hierarchical structure obtained in the embodiment is basically similar to that of the lithium titanate material shown in FIG. 2.

The discharge capacity test results of the lithium ion battery using the lithium titanate material with the linear hierarchical structure obtained in this example as the electrode material at different charge and discharge rates are shown in fig. 4. It can be seen that the following properties are exhibited due to the material structure: (1) the linear structures have a large aspect ratio, mainly 10 to 100, which can be much larger compared to nanoparticlesThe grain boundary among the particles is reduced, so that the effective migration of electrons in the long axis direction is facilitated, and the overall conductivity of the electrode material is improved; (2) the thickness of the nanosheet with the flaky hierarchical structure is mainly 1-10 nanometers, and the nanosheet has a very short lithium ion migration path, so that the intercalation and deintercalation processes of lithium ions can be rapidly promoted, and the multiplying power charge and discharge performance can be promoted; (3) the hierarchical structure has a large specific surface area, which is beneficial to the contact area of the electrolyte and the electrode and reduces the current density; (4) the linear hierarchical structure is easy to be fully and uniformly mixed with the conductive agent, the effective conductive contact between the wires is increased, and the effective transportation of electrons is promoted. Therefore, the lithium titanate material with the structure has excellent charge and discharge performance of the lithium ion battery, and the average battery capacity is respectively maintained at 227, 207, 194, 182, 178, 173 and 167mAhg at different charge and discharge rates of 1C, 2C, 5C, 10C, 15C, 20C and 50C^-1Especially, 167mAhg can be kept under the ultra-fast charge and discharge rate of 50C^-1The discharge capacity of the lithium titanate is far higher than that of other reported linear lithium titanate materials.

Example 3

According to the flow of the figure 1, under the stirring condition, 0.3 g of titanium tetrafluoride is dispersed and dissolved in 100ml of aqueous solution to form a solution, then tetramethyl ammonium hydroxide with the concentration of 0.10 mol per liter is slowly dripped into the solution until the solution is neutral, so that the titanium tetrafluoride is gradually and completely hydrolyzed to generate hydrous titanic acid precipitate, then the hydrous titanic acid precipitate is ultrasonically dispersed, washed with deionized water for multiple times, and centrifugally separated. Next, hydrogen peroxide and lithium hydroxide were dissolved in water to form an aqueous solution having a lithium hydroxide concentration of 0.4 mole per liter and a hydrogen peroxide volume fraction of 1%. Subsequently, the hydrous titanic acid precipitate after the above centrifugal separation was dispersed in 100ml of the aqueous hydrogen peroxide solution containing lithium hydroxide prepared above, and stirred to form a yellow transparent solution. Then, the above yellow transparent solution was heated to 60 ℃ and stirred at a constant temperature for 24 hours, and the reaction was stopped and separated to obtain a white solid. Subsequently, the white solid was placed in an oven and dried under vacuum at 30 ℃ for 24 hours. Subsequently, the dried white solid powder was dispersed in 100mL of an ethanol solution containing forty percent pure water, and reacted at 120 ℃ for 6 hours to obtain a lithium titanate product having a linear hierarchical structure. The SEM image of the obtained linear-graded lithium titanate is close to fig. 2.

The test result of the discharge capacity of the lithium ion battery using the lithium titanate with the linear hierarchical structure of the present embodiment as the electrode material is close to that in fig. 3.

Example 4

According to the flow of figure 1, 6 g of titanium tetrachloride is dispersed and dissolved in 100ml of aqueous solution under the condition of stirring to form solution, then potassium hydroxide with the concentration of 0.10 mol per liter is slowly dripped into the solution until the solution is neutral, the titanium tetrachloride is gradually and completely hydrolyzed to generate hydrous titanic acid precipitate, then the hydrous titanic acid precipitate is ultrasonically dispersed, washed with deionized water for multiple times, and centrifugally separated. Next, hydrogen peroxide and lithium hydroxide were dissolved in water to form an aqueous solution having a lithium hydroxide concentration of 1.0 mole per liter and a hydrogen peroxide volume fraction of 8%. Subsequently, the hydrous titanic acid precipitate after the above centrifugal separation was dispersed in 100ml of the aqueous hydrogen peroxide solution containing lithium hydroxide prepared above, and stirred to form a yellow transparent solution. Then, the above yellow transparent solution was heated to 100 ℃ and stirred at a constant temperature for 1 hour, and the reaction was stopped and separated to obtain a white solid. Subsequently, the white solid was put into an oven and dried at 80 ℃ for 12 hours. Subsequently, the above-mentioned dried white solid powder was dispersed in 100mL of an aqueous solution containing 0.01mol per liter of nitric acid, and reacted at 150 ℃ for 1 hour to obtain a lithium titanate product having a linear hierarchical structure. Subsequently, the lithium titanate having the linear hierarchical structure is placed in a muffle furnace and heated at 300 ℃ for 12 hours to obtain lithium titanate having a linear hierarchical structure. The SEM image of the obtained linear-graded lithium titanate is close to fig. 2.

The test result of the discharge capacity of the lithium ion battery using the lithium titanate with the linear hierarchical structure of the present embodiment as the electrode material is close to that in fig. 4.

Example 5

According to the flow of the figure 1, 3 g of titanium isopropoxide is dispersed in 100ml of aqueous solution under the stirring condition to be directly hydrolyzed to form hydrous titanic acid precipitate, then the hydrous titanic acid precipitate is ultrasonically dispersed, washed by deionized water for multiple times, and centrifugally separated. Next, hydrogen peroxide and lithium hydroxide were dissolved in water to form an aqueous solution having a lithium hydroxide concentration of 0.8 mole per liter and a hydrogen peroxide volume fraction of 5%. Subsequently, the hydrous titanic acid precipitate after the above centrifugal separation was dispersed in 100ml of the aqueous hydrogen peroxide solution containing lithium hydroxide prepared above, and stirred to form a yellow transparent solution. Then, the above yellow transparent solution was heated to 80 ℃ and stirred at a constant temperature for 4 hours, the reaction was stopped and a white solid was isolated. Subsequently, the white solid was put into an oven and dried at 70 ℃ for 15 hours. Subsequently, the dried white solid powder was dispersed in 150mL of an aqueous solution containing 0.1mol/l of lithium hydroxide, and reacted at 130 ℃ for 8 hours to obtain a lithium titanate product having a linear hierarchical structure. Subsequently, the lithium titanate having the linear hierarchical structure is placed in a muffle furnace and heated at 700 ℃ for 1 hour to obtain lithium titanate having a linear hierarchical structure. The SEM image of the obtained linear-graded lithium titanate is close to fig. 2.

Example 6

According to the scheme of FIG. 1, first, hydrogen peroxide and lithium hydroxide are dissolved in water to form 100ml of an aqueous solution having a lithium hydroxide concentration of 0.9 mol/L and a hydrogen peroxide volume fraction of 3%. Under stirring, 1 g of titanyl sulfate was slowly added to the above aqueous solution, and stirred to form a yellow transparent solution. Subsequently, the above yellow transparent solution was heated to 70 ℃ and stirred at a constant temperature for 8 hours, the reaction was stopped and a white solid was isolated. The white solid was then placed in an oven and dried at 60 degrees celsius for 20 hours. Subsequently, the above-mentioned dried white solid powder was dispersed in 100mL of pure water and reacted at 100 ℃ for 5 hours to obtain a lithium titanate product having a linear hierarchical structure. The SEM image of the obtained linear-graded lithium titanate is close to fig. 2.

Example 7

According to the scheme of FIG. 1, first, hydrogen peroxide and lithium hydroxide are dissolved in water to form 100ml of an aqueous solution having a lithium hydroxide concentration of 0.6 mol/L and a hydrogen peroxide volume fraction of 2%. Under stirring, 1 g of tetrabutyl titanate was slowly added to the above aqueous solution, and stirred to form a yellow transparent solution. Subsequently, the above yellow transparent solution was heated to 80 ℃ and stirred at a constant temperature for 5 hours, the reaction was stopped and a white solid was isolated. The white solid was then placed in an oven and dried under vacuum at 60 degrees celsius for 20 hours. Subsequently, the above-mentioned dried white solid powder was dispersed in 100mL of pure water containing tetradecaethanol, and reacted at 90 ℃ for 15 hours to obtain a lithium titanate product having a linear hierarchical structure. The SEM image of the obtained linear-graded lithium titanate is close to fig. 2.

Example 8

The lithium titanate having a linear hierarchical structure prepared in example 1 was separated, and then placed in an oven and dried at 120 ℃ for 24 hours. And then, washing and separating the dried lithium titanate with the linear hierarchical structure for multiple times by using deionized water, then putting the washed lithium titanate into a nitric acid solution of 0.01mol/L for hydrogen ion exchange, washing the lithium titanate with deionized water for multiple times after the hydrogen ion exchange until the pH value of a washing solution is close to neutral, and then separating and drying to obtain the titanic acid with the linear hierarchical structure.

The results of the discharge capacity test of the sodium-ion battery using the linear graded-structure titanic acid material obtained in this example as the electrode material at different charge and discharge rates are shown in fig. 5. The preparation of the sodium ion battery electrode adopts a blade coating method, and firstly, according to a titanic acid product: super P: polyvinylidene fluoride (PVDF) is in a mass ratio of 7:2:1, N-methyl pyrrolidone (NMP) is used as a solvent to be mixed into slurry, a blade coater is used for uniformly coating the slurry on a copper foil, then metal lithium is used as a counter electrode in a glove box, and 1mol/L NaClO is adopted as electrolyte₄Dissolving in EC/DMC (volume ratio of 1:1) and adding 2% volume fraction of FEC as additive and Glass Fiber as separator, assembling into type CElectrochemical testing was performed on R2032 coin cells. As can be seen in fig. 5, the material structure has the following characteristics: (1) the linear structure has a large length-diameter ratio which is mainly 10 to 100, and compared with nano particles, the linear structure can greatly reduce grain boundaries among the particles, is favorable for effective migration of electrons in the long axis direction, and improves the overall conductivity of the electrode material; (2) the thickness of the nanosheet with the flaky hierarchical structure is mainly 1-10 nanometers, and the nanosheet has a very short lithium ion migration path, can quickly promote the intercalation and deintercalation processes of sodium ions, and promotes the multiplying power charge-discharge performance; (3) the hierarchical structure has a large specific surface area, which is beneficial to the contact area of the electrolyte and the electrode and reduces the current density; (4) the linear hierarchical structure is easy to be fully and uniformly mixed with the conductive agent, the effective conductive contact between the wires is increased, and the effective transportation of electrons is promoted. Therefore, the titanic acid material with the structure has better charging and discharging performances of the sodium-ion battery, and the average capacity of the battery is respectively maintained at 151, 128, 111, 97, 88, 83 and 54mAhg under different charging and discharging rates of 1C, 2C, 5C, 10C, 15C, 20C and 50C^-1Higher than other reported titanic acid materials.

Example 9

The lithium titanate having a linear hierarchical structure prepared in example 1 was separated, and then placed in an oven and dried at 150 ℃ for 12 hours. And then, washing and separating the dried lithium titanate with the linear hierarchical structure for multiple times by using deionized water, then putting the washed lithium titanate into 0.05 mol/L hydrochloric acid solution for hydrogen ion exchange, washing the lithium titanate with deionized water for multiple times after the hydrogen ion exchange until the pH of the washing solution is close to neutral, and then separating and drying to obtain the titanic acid with the linear hierarchical structure. The discharge capacity test result of the sodium-ion battery using the linear hierarchical structure titanic acid of the present example as the electrode material is close to that of fig. 5.

Example 10

The lithium titanate having a linear hierarchical structure prepared in example 1 was separated, and then placed in an oven and dried at 200 ℃ for 4 hours. And then, washing and separating the dried lithium titanate with the linear hierarchical structure for multiple times by using deionized water, then putting the washed lithium titanate into 0.1mol/L acetic acid solution for hydrogen ion exchange, washing the lithium titanate with deionized water for multiple times after the hydrogen ion exchange until the pH value of the washing solution is close to neutral, and then separating and drying to obtain the titanic acid with the linear hierarchical structure. The discharge capacity test result of the sodium-ion battery using the linear hierarchical structure titanic acid of the present example as the electrode material is close to that of fig. 5.

Example 11

The linear hierarchical structure titanic acid prepared in example 8 was placed in a muffle furnace and annealed at 400 degrees celsius for 4 hours to obtain a linear hierarchical structure titanium dioxide. The SEM morphology of the linear hierarchical structure titania material obtained in this example is shown in fig. 6, where it can be seen that the product is a linear structure, the diameter of which is 20 nm to 1 micron, the length of which is 1 micron to 50 microns, and the aspect ratio of which is greater than 10; the linear structure is a linear hierarchical structure, the surface of the linear hierarchical structure is composed of nano-sheet particles, the size of the nano-sheet is mainly 5-100 nanometers, and the thickness of the nano-sheet is 1-10 nanometers. FIG. 7 is a graph showing the rate of photocatalytic degradation of rhodamine B by titanium dioxide obtained in this example. The test condition is that 50mg of the titanium dioxide product prepared in the embodiment is dispersed in 10mg/L rhodamine B solution, and a rate chart of photocatalytic degradation of rhodamine B under the irradiation of a 3-watt LED ultraviolet lamp is adopted; under the same test conditions, P25 was used as a comparative material. As can be seen in FIG. 7, the linear hierarchical structure is beneficial to the separation of electrons and holes, and increases the advantages of structural characteristics such as catalytic reaction active sites, and the like, so that the material has the performance of photocatalytic decomposition of organic matters higher than that of the conventional commercial P25 product, about 2.5 times of the rate of the P25 product, and has better application prospect of photocatalytic decomposition of organic pollutants.

Example 12

The linear hierarchical structure titanic acid prepared in example 8 was placed in a muffle furnace and annealed at 600 degrees celsius for 3 hours to obtain a linear hierarchical structure titanium dioxide. The SEM image of the linear hierarchical structure titanium dioxide of this example is close to fig. 6. The rate chart of photocatalytic degradation of rhodamine B for titanium dioxide obtained in this example is close to that of fig. 7.

Example 13

The linear hierarchical structure titanic acid prepared in example 8 was dispersed in 100ml of pure water and reacted at 180 ℃ for 6 hours to obtain a linear hierarchical structure titanium dioxide. The SEM image of the linear hierarchical structure titanium dioxide of this example is close to fig. 6. The rate chart of photocatalytic degradation of rhodamine B for titanium dioxide obtained in this example is close to that of fig. 7.

Example 14

The linear hierarchical structure titanic acid prepared in example 8 was dispersed in 100ml of a nitric acid solution having a concentration of 0.01mol per liter, and reacted at 150 ℃ for 12 hours to obtain a linear hierarchical structure titanium dioxide. The SEM image of the linear hierarchical structure titanium dioxide of this example is close to fig. 6. The rate chart of photocatalytic degradation of rhodamine B for titanium dioxide obtained in this example is close to that of fig. 7.

Example 15

The linear hierarchical structure titanic acid prepared in example 8 was dispersed in 100ml of an aqueous ammonia solution having a concentration of 0.01mol per liter, and reacted at 120 ℃ for 24 hours to obtain a linear hierarchical structure titanium dioxide. The SEM image of the linear hierarchical structure titanium dioxide of this example is close to fig. 6. The rate chart of photocatalytic degradation of rhodamine B for titanium dioxide obtained in this example is close to that of fig. 7.

Example 16

The linear hierarchical structure titanic acid prepared in example 8 was dispersed in 100ml of a hydrofluoric acid solution having a concentration of 0.05 mol per liter, and reacted at 150 degrees celsius for 6 hours. And then, separating and drying a product obtained by the hydrothermal reaction, putting the product into a muffle furnace, and annealing the product for 3 hours at 550 ℃ to obtain the linear hierarchical structure titanium dioxide. The SEM image of the linear hierarchical structure titanium dioxide of this example is close to fig. 6. The rate chart of photocatalytic degradation of rhodamine B for titanium dioxide obtained in this example is close to that of fig. 7.

Claims

1. A preparation method of linear hierarchical structure lithium titanate is provided, wherein the method comprises the following steps:

(S1) dispersing a titanium source in an aqueous hydrogen peroxide solution containing lithium hydroxide to obtain a transparent solution; the molar ratio of hydrogen peroxide to the titanium source in the aqueous hydrogen peroxide solution is greater than or equal to 3: 1; the concentration of lithium hydroxide in the aqueous solution of hydrogen peroxide containing lithium hydroxide is 0.4-1.0 mol/L, and the volume fraction of hydrogen peroxide is 0.5-10%;

(S2) heating the transparent solution obtained in the step (S1) to 60-100 ℃ for reaction to obtain a precursor with a linear structure;

(S3) separating the linear structure precursor obtained in the step (S2) and drying the precursor; the drying temperature is 20-80 ℃;

(S4) hydrothermally reacting the linear structure precursor dried in the step (S3) to obtain the linear hierarchical structure lithium titanate; the reaction temperature of the hydrothermal reaction is 80 ℃ to 150 ℃.

2. The production method according to claim 1, wherein the molar ratio of hydrogen peroxide to the titanium source in the aqueous hydrogen peroxide solution of step (S1) is (4-6): 1.

3. the production method according to claim 1, wherein step (S4) further comprises annealing a product obtained by hydrothermal reaction to obtain the linear-shaped hierarchical structure lithium titanate.

4. The production method according to claim 3, wherein the temperature of the annealing treatment is 300 ℃ to 700 ℃; the time of the annealing treatment is 1h to 24 h.

5. The production method according to claim 1, wherein the titanium source is selected from one or a combination of more of hydrous titanic acid, titanium ethoxide, titanium isopropoxide, tetrabutyl titanate, titanium ethoxide, titanium propoxide, titanium sulfate, titanyl sulfate, titanium tetrachloride, titanium tetrafluoride, ammonium fluorotitanate, titanium nitride, titanium dioxide, and metatitanic acid.

6. The production method according to claim 1, wherein the titanium source is orthotitanic acid.

7. The production method according to claim 5, wherein the hydrous titanic acid is obtained by hydrolysis of a titanium-containing compound.

8. The production method according to claim 7, wherein the titanium-containing compound is selected from one or a combination of more of titanium ethoxide, titanium isopropoxide, tetrabutyl titanate, titanium ethoxide, titanium propoxide, titanium sulfate, titanyl sulfate, titanium tetrachloride, titanium tetrafluoride, and ammonium fluorotitanate.

9. The production method according to claim 7, wherein the hydrolysis reaction is a direct hydrolysis in which the titanium-containing compound is dispersed in water to obtain hydrous titanic acid, or a hydrolysis in which the titanium-containing compound is dispersed in an aqueous solution containing an alkaline substance to obtain hydrous titanic acid.

10. The production method according to claim 9, wherein the basic substance is selected from a combination of one or more of ammonia, sodium hydroxide, potassium hydroxide, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, ethylenediamine, diethylamine, triethylamine, ethylamine, ethanolamine, and diethanolamine.

11. The production method according to claim 7, wherein the titanium-containing compound is further purified after the hydrolysis reaction to obtain the hydrous titanic acid.

12. The production method according to claim 11, wherein the purity of the hydrous titanic acid obtained through purification is 97% or more.

13. The method of claim 11, wherein the purification is selected from a combination of one or more of water washing-centrifugation, water washing-membrane separation, water washing-filtration, and dialysis.

14. The production method according to claim 1, wherein the heating in the step (S2) is carried out for a reaction time of 0.5 to 24 hours.

15. The method of claim 1, wherein the drying in step (S3) is selected from low-temperature drying and/or vacuum drying.

16. The method according to claim 1, wherein the time for the hot liquid reaction in the step (S4) is 1 to 24 hours.

17. The production method according to any one of claims 1 to 16, further comprising a step of, after hydrothermal reaction in the step (S4) to obtain the linear-shaped lithium titanate having a hierarchical structure, surface-modifying the obtained linear-shaped lithium titanate having a hierarchical structure.

18. The preparation method of claim 17, wherein the surface modification is to load a linear hierarchical structure lithium titanate surface with a combination of one or more selected from carbon nanotubes, graphene, black phosphorus, and metals.

19. A linear hierarchical structure lithium titanate produced by the production method according to any one of claims 1 to 18.

20. An electrode material for an ion battery, wherein a raw material for producing the electrode material comprises the linear hierarchical structure lithium titanate according to claim 19.

21. The electrode material of claim 20, wherein the ion battery is a lithium ion battery, a sodium ion battery, a potassium ion battery, or a magnesium ion battery.

22. A method for producing a linear hierarchical structure titanic acid, comprising subjecting the linear hierarchical structure lithium titanate according to claim 19 to acid exchange to obtain the linear hierarchical structure titanic acid.

23. The preparation method according to claim 22, wherein the acid exchange comprises putting the nano-scale hierarchical structure lithium titanate into an acid solution to perform hydrogen ion exchange to obtain the linear hierarchical structure titanic acid, wherein the concentration of the acid in the acid solution is 0.01mol/L-0.1 mol/L.

24. The method of claim 23, wherein the acid is selected from the group consisting of nitric acid, hydrochloric acid, sulfuric acid, and acetic acid.

25. The production method according to claim 23, further comprising a step of washing the linear graded-structure titanic acid prior to the acid exchange, and then subjecting the washed linear graded-structure titanic acid to an acid exchange treatment, and then washing and drying the linear graded-structure titanic acid obtained by the acid exchange treatment.

26. A linear hierarchical structure titanic acid produced by the production method according to any one of claims 22 to 25.

27. Use of the linear graded titanic acid of claim 26 in the preparation of an ion battery or for pollutant adsorption.

28. The use of claim 27, wherein the ion battery is a lithium ion battery, a sodium ion battery, a potassium ion battery, or a magnesium ion battery.

29. A method for producing a linear-shaped hierarchical-structure titanium dioxide, which comprises subjecting the linear-shaped hierarchical-structure titanic acid according to claim 26 to hydrothermal reaction and/or annealing treatment to obtain the linear-shaped hierarchical-structure titanium dioxide.

30. The preparation method according to claim 29, wherein a reaction system of the hydrothermal reaction is a neutral water system, an acidic water system, or a basic water system; the temperature of the hydrothermal reaction is 100-200 ℃.

31. The method of claim 30, wherein the hydrothermal reaction is carried out for a period of time ranging from 1 hour to 24 hours.

32. The method of any one of claims 29 to 31, wherein the annealing is performed at a temperature of 350 ℃ to 800 ℃.

33. The production method according to claim 32, wherein the time of the annealing treatment is 1h to 24 h.

34. The titanium dioxide having a linear hierarchical structure produced by the production method according to any one of claims 29 to 33.

35. Use of the linear graded-structure titanium dioxide according to claim 34 in photocatalytic degradation of organic pollutants, in the biomedical field and in the preparation of hydrogenation catalysts, dye-sensitized solar cells, perovskite solar cells, hydrophilic materials, and hydrophobic materials.