Process for preparing titanic acid salt, titanic acid, and titanium oxide having controllable particle size and hierarchical structure

Technical field

0001The present invention relates to a process for preparing a titanic acid salt, titanic acid, and titanium oxide having a controllable particle size and a hierarchical structure, and belongs to the technical field of energy and environmental protection materials.

Background Art

0002Titanic acid salt, titanic acid, and titanium oxide have been widely used in the technical fields of lithium ion batteries, potassium ion batteries, sodium ion batteries, catalysis, photocatalysis, solar cells, water photolysis, sensing, biology and the like, and is a hotspot for the research in the material field.

0003Various application performances of titanic acid salts, titanic acid and titanium oxide materials are closely related to their morphology and structure. The one-dimensional structure mainly includes nanowires, nanorods, nanotubes and nanoribbons. Among them, the nanotubes have two surfaces, inner surface and outer surface, so that they have a high specific surface area, and have good advantages in the research and application of one-dimensional material structure, and have received much attention. As compared with single crystal nanoparticles, one-dimensional linear nanomaterials can reduce the grain boundary between particles and facilitate the transport of carriers in the longitudinal direction. They have the following characteristics: (1) at the nanometer scale, the specific surface area and active sites increase dramatically material, which can greatly accelerate the reaction on the surface and the interaction with the media; (2) in the photocatalysis field, the free movement of photogenerated electron-hole pair in the longitudinal direction will be facilitated, the recombination probability of electrons and holes will be reduced and the photocatalytic efficiency will be improved; (3) in the field of battery electrode materials, the long axis is beneficial for the effective migration of electrons, and the short axis is beneficial for the rapid intercalation and deintercalation process of lithium, sodium or potassium ions; in addition, the one-dimensional nanostructures have better charge-discharge performance, as compared with the nanoparticles; (4) in the field of solar cells, the one-dimensional structure can greatly reduce the grain boundaries between particles, facilitate the transport of electrons in the photoanode, and greatly improve the efficiency for collecting and converting electrons in the battery and the like.

0004In recent years, since the hierarchical structure has a high degree of order, and can achieve a variety of functions, its design and development has received many attentions. The hierarchical structure can increase the specific surface area of the material, increase the order of contact of the nanoparticles, and enhance the effective migration of electrons. However, the currently reported hierarchical structure for titanic acid salt, titanic acid salt and titanium oxide cannot achieve the effective regulation of particle size of nanowires and nanotubes in the hierarchical structure, or the regulation of particle size of the hierarchical structure material. Thus, it is one of the problems to be solved urgentlyin the art to find and realize the effective regulation of structure and morphology of the constituents in the hierarchical structure of titanic acid salt, titanic acid salt and titanium oxide and the particle size of spherical particles in the hierarchical structure, and design the desired material which may be used to construct multifunctional nanoscale device through reasonable experimentation and regulation.

SUMMARY OF INVENTION

0005To solve the above technical problems, an object of the present invention is to provide processes for preparing titanic acid salts, titanic acid, and titanium oxide having a controllable particle size and a hierarchical structure, which can synthesize titanic acid salts, titanic acid, and titanium oxide product having a hierarchical structure with controllable particle size and constituent morphology and structure, and find the morphology and structure of the material with the best performance, by adding a polymer in the reaction system and adjusting the amount of the polymer.

0006In order to achieve the above object, the present invention firstly provides a process for preparing a titanic acid salt having a controllable particle size and a hierarchical structure, wherein the process comprises the steps of: <ul id="ul0001" list-style="none" compact="compact"><li>S1, preparing a titanium-containing peroxo-complex solution;</li><li>S2, adding a basic metal compound to the titanium-containing peroxo-complex solution to form a mixture solution;</li><li>S3, adding a polymer to the mixture solution to form a precursor dispersion; the polymer includes one of polyvinyl alcohol, hydroxypropyl methyl cellulose, and polyethylene glycol; and</li><li>S4, subjecting the precursor dispersion to a solvothermal reaction to obtain the titanic acid salt having a hierarchical structure.</li></ul>

0007In the process for preparing the titanic acid salt having a hierarchical structure, preferably the prepared titanic acid salt mainly includes but is not limited to, one or more of lithium titanate, sodium titanate, potassium titanate, and the like.

0008In the process for preparing the titanic acid salt having a hierarchical structure, preferably, the hierarchical structure mainly includes, but is not limited to, one or more of a spherical hierarchical structure composed of nanoplatelet particles, a spherical hierarchical structure composed of nanotube particles, a spherical hierarchical structure composed of nanowire particles, and the like.

0009In the process for preparing the titanic acid salt having a hierarchical structure, preferably, in S1, the process for preparing the titanium-containing peroxo-complex solution is carried out by dispersing a titanium source in an aqueous hydrogen peroxide solution to form a solution; preferably, the molar concentration ratio of the titanium source to the hydrogen peroxide is 1:3 to 1:6; preferably, the titanium source used is one or more selected from the group consisting of titanium metal, titanium ethoxide, titanium propoxide, tetrabutyl titanate, titanium glycolate, titanium glyceroxide, titanium sulfate, titanium oxysulfate, titanium tetrachloride, titanium tetrafluoride, ammonium fluorotitanate, titanium nitride, titanium oxide, metatitanic acid, orthotitanic acid and the like. The dispersing is carried out by one or more selected from dispersion under agitation, ultrasonic dispersion and the like. The dispersing is preferably carried out at a temperature of from 10 degrees Celsius to 100 degrees Celsius.

0010The aqueous hydrogen peroxide solution may be one selected from the group consisting of an acidic aqueous hydrogen peroxide solution, a neutral aqueous hydrogen peroxide solution, and an alkaline aqueous hydrogen peroxide solution; wherein the acidic aqueous hydrogen peroxide solution is adjusted to be acidic with one or more of sulfuric acid, hydrochloric acid, nitric acid and acetic acid; the alkaline aqueous hydrogen peroxide solution is adjusted to be alkaline with one or more of aqueous ammonia, sodium hydroxide, lithium hydroxide, potassium hydroxide, and organic amine.

0011When the titanium source is dispersed in an aqueous hydrogen peroxide solution to form a solution for preparing the titanium-containing peroxo-complex solution, the titanium source may be hydrated titanic acid (containing only Ti, O, and H, without metal ions or other organic compounds, no impurities); and the hydrated titanic acid may be obtained from a titanium-containing compound by a hydrolysis reaction. The titanium-containing compound may be one or more selected from the group consisting of titanium ethoxide, titanium propoxide, tetrabutyl titanate, titanium glycolate, titanium glyceroxide, titanium sulfate, titanium oxysulfate, titanium tetrachloride, titanium tetrafluoride, ammonium fluorotitanate, industrial titanium-containing compounds and the like. The hydrolysis reaction is carried out by dispersing the titanium-containing compound in pure water for direct hydrolysis to form the hydrated titanic acid, or the hydrolysis reaction is carried out by dispersing the titanium-containing compound in an aqueous solution containing a basic substance for hydrolysis to form the hydrated titanic acid. The basic substance is one or more selected from the group consisting of aqueous ammonia, sodium hydroxide, potassium hydroxide, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, ethylenediamine, diethylamine, triethylamine, ethylamine, ethanolamine, diethanolamine and the like. The above process for dispersing the titanium source in an aqueous hydrogen peroxide solution to form a solution for preparing the titanium-containing peroxo-complex solution, is to subject the titanium-containing compound to the hydrolysis reaction and then purify to obtain the hydrated titanic acid; the purification is used to remove impurity ions to obtain the hydrated titanic acid having a purity of 97% or more; the purification may be carried out by one or more of water washing-separation by centrifugation, water washing-membrane separation, water washing-filtration and dialysis.

0012In the process for preparing the titanic acid salt having a hierarchical structure, preferably in S2, the concentration of the basic metal compound in the mixture solution is 0.05 mol/L to 0.4 mol/L; more preferably, the concentration is 0.10 mol/L to 0.35 mol/L. Preferably, the molar ratio of the titanium source to the basic metal compound is 1:100 to 1:1.

0013In the process for preparing the titanic acid salt having a hierarchical structure, preferably in S2, the basic metal compound used is one or more selected from the group consisting of a basic metal oxide, a basic metal peroxide, a basic metal superoxide, a basic metal hydroxide and the like. The metal element in the basic metal compound may be one or more selected from lithium, sodium, and potassium.

0014In the process for preparing the titanic acid salt having a hierarchical structure, preferably in S2, the basic metal compound is added in the form of a solid or an aqueous solution. Meanwhile, during the addition, the rate of addition of the metal compound is controlled so that it is added slowly.

0015In the process for preparing the titanic acid salt having a hierarchical structure, in S3, the addition of the polymer (one of polyvinyl alcohol, hydroxypropyl methyl cellulose, and polyethylene glycol) can regulate the morphology and particle size of the titanic acid salt product having a hierarchical structure. The mechanism after addition is that the substance such as polyvinyl alcohol, hydroxypropyl methyl cellulose, or polyethylene glycol has an advantages of being relatively stable under a high temperature and a basic condition, can make the titanium peroxo-complex more stable, and control the nucleation and growth rate of the titanic acid salt during the solvothermal reaction under a strong alkaline condition, while the substance such as polyvinyl alcohol, hydroxypropyl methyl cellulose, or polyethylene glycol can also increase the viscosity of the precursor dispersion, reduce the diffusion rate of ions, and in turn control the particle size. In addition, polyvinyl alcohol, hydroxypropyl methylcellulose, polyethylene glycol, and the like also have application advantages such as abundant sources and low prices.

0016In the process for preparing the titanic acid salt having a hierarchical structure, preferably in S3, the content by mass of the polymer (one of polyvinyl alcohol, hydroxypropyl methyl cellulose, and polyethylene glycol) in the precursor dispersion is 0.01% to 10%; preferably the content is from 0.1% to 1%.

0017In the process for preparing the titanic acid salt having a hierarchical structure, preferably in S3, the polymer (one of polyvinyl alcohol, hydroxypropyl methyl cellulose, and polyethylene glycol) is added in the form of a solid or an aqueous solution.

0018In the process for preparing the titanic acid salt having a hierarchical structure, preferably, the precursor dispersion may be one of a solution (transparent solution), an emulsion, a suspension, and the like.

0019In the process for preparing the titanic acid salt having a hierarchical structure, preferably in S4, the solvothermal reaction is carried out at a temperature of 80 degrees Celsius to 200 degrees Celsius; the solvothermal reaction is carried out for 1 to 24 hours.

0020The process for preparing the titanic acid salt having a hierarchical structure provided by the present invention can not only realize the regulation of morphology and particle diameter of constituent units in the hierarchical structure, but also can achieve the regulation of particle size in the hierarchical structure, which cannot be achieved by other processes.

0021The present invention also provides a titanic acid salt having a hierarchical structure prepared by the above preparation process.

0022The present invention also provides a process for surface modifying the titanic acid salt having a hierarchical structure, which can increase the conductivity of the titanic acid salt through surface modification. Preferably, the surface modification includes one or more of supporting carbon, supporting carbon nanotubes, supporting graphene, supporting black phosphorus, supporting a metal and the like.

0023The present invention also provides use of the titanic acid salt having a hierarchical structure as an electrode material in an ion battery; preferably, the ion battery is one or more selected from a lithium ion battery, a sodium ion battery, a potassium ion battery, and a magnesium ion battery.

0024The present invention also provides a process for preparing titanic acid, wherein the process comprises the step of: subjecting the titanic acid salt having a hierarchical structure prepared according to the present invention to an acid exchange process to obtain the titanic acid having a hierarchical structure. Preferably, the acid exchange process comprises: drying, washing and separating the titanic acid salt having a hierarchical structure; and placing the separated titanic acid salt having a hierarchical structure in an acid solution for hydrogen ion exchange to obtain the titanic acid having a hierarchical structure. The acid solution used may be one or more selected from nitric acid, hydrochloric acid, sulfuric acid, acetic acid and the like, and the concentration of the acid solution is 0.001 mol/L to 0.1 mol/L.

0025According to a particular embodiment of the invention, the process for preparing titanic acid may comprise the steps of: separating and drying the titanic acid salt having a hierarchical structure; and subjecting the dried titanic acid salt having a hierarchical structure to washing and separation for several times; placing the washed and separated titanic acid salt having a hierarchical structure in an acid solution for hydrogen ion exchange to obtain the titanic acid product having a hierarchical structure; and washing, separating and drying the obtained titanic acid product having a hierarchical structure to obtain the titanic acid having a hierarchical structure.

0026The present invention also provides the titanic acid having a hierarchical structure prepared by the above preparation process.

0027The present invention also provides use of the titanic acid having a hierarchical structure as an electrode material or a contaminant adsorbent in an ion battery; preferably, the ion battery is one or more selected from a lithium ion battery, a sodium ion battery, a potassium ion battery, a magnesium ion battery, and the like.

0028The present invention also provides a process for preparing titanium oxide, comprising the steps of: subjecting the titanic acid having a hierarchical structure to hydrothermal reaction and/or annealing to obtain the titanium oxide having a hierarchical structure. The system for the hydrothermal reaction is one selected from a pure water system, an acidic water system, and an alkaline water system. The hydrothermal reaction may be carried out at a temperature of 100 degrees Celsius to 200 degrees Celsius; and the hydrothermal reaction may be carried out for 1 to 24 hours; the annealing may be carried out at a temperature of 300 degrees Celsius to 700 degrees Celsius; and the annealing may be carried out for 1 to 24 hours.

0029The present invention also provides the titanium oxide having a hierarchical structure prepared by the above preparation process.

0030The invention also provides use of the titanium oxide having a hierarchical structure in one or more of catalytic hydrogenation of a material, photocatalytic degradation of organic contaminants, hydrogen production by photocatalytic decomposition of water, gas sensing, dye-sensitized solar cell, perovskite solar cell, hydrophilic or hydrophobic material, biomedical field and the like.

0031The process for preparing the titanic acid salt, titanic acid and titanium oxide having the hierarchical structure provided by the present invention may be as shown in <figref idref="f0001">FIG. 1</figref>. The prepared titanic acid salt, titanic acid and titanium oxide according to the present invention are microbeads of a hierarchical structure composed of one-dimensional nanotubes or nanowires, and are beneficial for improving the application effects of the material in the fields of battery electrodes, catalysis, photocatalysis, sensing, solar cells, hydrophilicity or hydrophobicity, biology, and the like.

0032The advantages of the present invention are: <ol id="ol0001" compact="compact" ol-style=""><li>(1) The process for preparing a titanic acid salt, titanic acid, and titanium oxide having a controllable particle size and a hierarchical structure provided by the present invention can not only realize the regulation of morphology and particle diameter of constituent units in the hierarchical structure, but also can achieve the regulation of particle size in the hierarchical structure, which cannot be achieved by other processes.</li><li>(2) The process provided by the present invention can produce titanic acid salt microbeads having a hierarchical structure with a particle size less than 100 nanometers, which cannot be achieved by other processes.</li><li>(3) The product obtained by the process provided by the present invention has controllable structure and particle size, and it can produce functional materials or devices applicable in the fields of a storage battery, photocatalysis, a solar cell, sensing, biomedical, contaminant adsorption and processing, or the like, by designing the morphology and structure of the material.</li><li>(4) The process provided by the present invention has a simple process, and easily controllable process parameters, and is easy to scale to the industrial production.</li><li>(5) The process provided by the present invention uses a readily available raw material, and has a low production cost.</li></ol>

DESCRIPTION OF DRAWINGS

0033<ul id="ul0002" list-style="none" compact="compact"><li><figref idref="f0001">FIG. 1</figref> is a schematic flow diagram of the preparation process of the titanic acid salt, titanic acid, and titanium oxide having a controllable particle size and a hierarchical structure provided by the present invention.</li><li><figref idref="f0002">FIG. 2</figref> is a SEM photograph of the morphology and structure of the sodium titanate microbead product having a hierarchical structure produced in Example 1.</li><li><figref idref="f0002">FIG. 3</figref> is a SEM photograph of the morphology and structure of the sodium titanate microbead product having a hierarchical structure produced in Example 2.</li><li><figref idref="f0002">FIG. 4</figref> is a SEM photograph of the morphology and structure of the sodium titanate microbead product having a hierarchical structure produced in Example 3.</li><li><figref idref="f0003">FIG. 5</figref> is a SEM photograph of the morphology and structure of the sodium titanate microbead product having a hierarchical structure produced in Example 4.</li><li><figref idref="f0003">FIG. 6</figref> is a SEM photograph of the morphology and structure of the sodium titanate microbead product having a hierarchical structure produced in Example 5.</li><li><figref idref="f0003">FIG. 7</figref> is a SEM photograph of the morphology and structure of the sodium titanate microbead product having a hierarchical structure produced in Example 6.</li><li><figref idref="f0004">FIG. 8</figref> is a SEM photograph of the morphology and structure of the lithium titanate microbead product having a hierarchical structure produced in Example 7.</li><li><figref idref="f0004">FIG. 9</figref> is a SEM photograph of the morphology and structure of the lithium titanate microbead product having a hierarchical structure produced in Example 8.</li><li><figref idref="f0004">FIG. 10</figref> is a SEM photograph of the morphology and structure of the potassium titanate microbead product having a hierarchical structure produced in Example 9.</li><li><figref idref="f0005">FIG. 11</figref> is a SEM photograph of the morphology and structure of the sodium titanate microbead product having a hierarchical structure produced in Comparative Example 1.</li><li><figref idref="f0005">FIG. 12</figref> is a SEM photograph of the morphology and structure of the lithium titanate microbead product having a hierarchical structure produced in Comparative Example 2.</li><li><figref idref="f0005">FIG. 13</figref> is a SEM photograph of the morphology and structure of the potassium titanate microbead product having a hierarchical structure produced in Comparative Example 3.</li><li><figref idref="f0006">FIG. 14</figref> is a chart of discharge capacity of the sodium ion battery containing the sodium titanate microbead product having a hierarchical structure and different particle sizes obtained in Examples 1 to 4 and Comparative Example 1, at different charge/discharge rates.</li><li><figref idref="f0006">FIG. 15</figref> is a chart of discharge capacity of the sodium ion battery containing the lithium titanate microbead product having a hierarchical structure and different particle sizes obtained in Examples 8 to 9 and Comparative Example 2, at different charge/discharge rates.</li></ul>

Detailed Description of Embodiments

0034In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solutions in the Examples of the present invention will be set forth clearly and completely with reference to the Examples of the present invention. It is obvious that the described Examples are merely part of the Examples of the present invention, rather than all Examples. Any other examples achieved by a person of ordinary skill in the art based on the examples of the present invention without inventive work shall fall within the scope of the present invention.

0035Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art to which the present invention belongs. Herein, the terms are used in the Description of the present invention for the purpose of describing particular embodiments, and are not intended to limit the present invention. The term "and/or" as used herein includes any and all combinations of one or more of the listed items.

0036Specific embodiments of the present invention are disclosed herein in detail and the modes, in which the principle of the present application can be applied, are set forth, by reference to the following description. It should be understood that the embodiments of the invention are not limited in scope. The embodiments of the present invention include many variations, modifications, and equivalents within the scope of spirit and paragraphs of the appended claims.

0037Features described and/or illustrated with respect to one embodiment may be used in one or more other embodiments in the same or similar manner, in combination with, or in place of, features in other embodiments.

0038It should be emphasized that the term "comprise/comprising", when used herein, refers to the presence of features, integers, steps or components, but does not preclude the presence or addition of one or more other features, integers, steps or components.

0039Any numerical value recited herein includes all values of the lower and upper values in increments of one unit from the lower limit to the upper limit, provided that there is an interval of at least two units between any lower value and any higher value. For example, if the value of the number of components or a process variable (e.g., temperature, pressure, time, etc.) is stated to be from 1 to 90, preferably from 20 to 80, more preferably from 30 to 70, it is intended that the values such as 15 to 85, 22 to 68, 43 to 51, and 30 to 32 are also explicitly listed in the specification. For a value less than 1, it is appropriately considered that one unit is 0.0001, 0.001, 0.01, or 0.1. These are merely examples that are intended to be expressly stated, and all possible combinations of numerical values recited between the minimum and maximum values are considered to be explicitly described in this specification in a similar manner.

0040Unless indicated otherwise, all ranges include endpoints and all numbers between the endpoints. "About" or "approximately" as used with a range applies to both endpoints of the range. Thus, "about 20 to 30" is intended to cover "about 20 to about 30", including at least the indicated endpoints.

0041All articles and references disclosed, including patent applications and publications, are hereby incorporated herein by reference for all purposes. The term "essentially consisting of" describing a combination shall include the determined elements, ingredients, components or steps, and other elements, ingredients, components or steps that do not substantially affect the basic novel characteristics of the combination. The use of the term "comprising" or "comprises" to described the combination of elements, ingredients, components or steps herein also contemplates embodiments essentially consisting of these elements, ingredients, components or steps. By using the term "may" herein, it is intended to mean that any of the described attributes included by "may" is optional.

0042Multiple elements, ingredients, components or steps can be provided by a single element, ingredient, component or step to be integrated. Alternatively, a single component, component, component or step to be integrated may be divided into multiple separate components, ingredients, components or steps. The disclosed term "a" or "an" used to describe the element, ingredient, component or step does not exclude other elements, ingredients, components or steps.

0043The principles of the present invention are described in detail below with reference to a plurality of examples.

Example 1

0044This Example provides a process for preparing sodium titanate having a hierarchical structure, which comprises the following steps: Under stirring, 2 g of titanium oxysulfate was dispersed and dissolved into 150 ml of water to form a solution, then aqueous ammonia at a concentration of 0.1 mol/L was slowly added dropwise to the solution until the solution was neutral, so that titanium oxysulfate was gradually and completely hydrolyzed to form a hydrated titanic acid precipitate. Subsequently, the hydrated titanic acid precipitate was ultrasonically dispersed, washed several times with deionized water, and separated by centrifugation. The separated hydrated titanic acid precipitate was ultrasonically dispersed in 180 ml of water, and 10 ml of 30% aqueous hydrogen peroxide solution was added under stirring to form a titanium-containing peroxo-complex solution. Subsequently, 1.6 g of sodium hydroxide was added to the peroxo-complex solution under stirring to form a pale yellow transparent solution. Then 10 ml of polyvinyl alcohol solution at a concentration of 5% was added to the above solution under stirring to form a precursor dispersion containing polyvinyl alcohol. Finally, the precursor dispersion containing polyvinyl alcohol was hydrothermally treated at 150 °C for 12 hours, to obtain sodium titanate microbead product having a hierarchical structure (the structure thereof is shown in <figref idref="f0002">FIG. 2</figref>).

Example 2

0045This Example provides a process for preparing sodium titanate having a hierarchical structure, which comprises the following steps: Under stirring, 2 g of titanium oxysulfate was dispersed and dissolved into 150 ml of water to form a solution, then aqueous ammonia at a concentration of 0.1 mol/L was slowly added dropwise to the solution until the solution was neutral, so that titanium oxysulfate was gradually and completely hydrolyzed to form a hydrated titanic acid precipitate. Subsequently, the hydrated titanic acid precipitate was ultrasonically dispersed, washed several times with deionized water, and separated by centrifugation. The separated hydrated titanic acid precipitate was ultrasonically dispersed in 170 ml of water, and 10 ml of 30% aqueous hydrogen peroxide solution was added under stirring to form a titanium-containing peroxo-complex solution. Subsequently, 1.6 g of sodium hydroxide was added to the peroxo-complex solution under stirring to form a pale yellow transparent solution. Then 20 ml of polyvinyl alcohol solution at a concentration of 5% was added to the above solution under stirring to form a precursor dispersion containing polyvinyl alcohol. Finally, the precursor dispersion containing polyvinyl alcohol was hydrothermally treated at 150 °C for 12 hours, to obtain sodium titanate microbead product having a hierarchical structure (the structure thereof is shown in <figref idref="f0002">FIG. 3</figref>).

Example 3

0046This Example provides a process for preparing sodium titanate having a hierarchical structure, which comprises the following steps: Under stirring, 2 g of titanium oxysulfate was dispersed and dissolved into 150 ml of water to form a solution, then aqueous ammonia at a concentration of 0.1 mol/L was slowly added dropwise to the solution until the solution was neutral, so that titanium oxysulfate was gradually and completely hydrolyzed to form a hydrated titanic acid precipitate. Subsequently, the hydrated titanic acid precipitate was ultrasonically dispersed, washed several times with deionized water, and separated by centrifugation. The separated hydrated titanic acid precipitate was ultrasonically dispersed in 150 ml of water, and 10 ml of 30% aqueous hydrogen peroxide solution was added under stirring to form a titanium-containing peroxo-complex solution. Subsequently, 1.6 g of sodium hydroxide was added to the peroxo-complex solution under stirring to form a pale yellow transparent solution. Then 40 ml of polyvinyl alcohol solution at a concentration of 5% was added to the above solution under stirring to form a precursor dispersion containing polyvinyl alcohol. Finally, the precursor dispersion containing polyvinyl alcohol was hydrothermally treated at 150 °C for 12 hours, to obtain sodium titanate microbead product having a hierarchical structure (the structure thereof is shown in <figref idref="f0002">FIG. 4</figref>).

Example 4

0047This Example provides a process for preparing sodium titanate having a hierarchical structure, which comprises the following steps: Under stirring, 2 g of titanium oxysulfate was dispersed and dissolved into 150 ml of water to form a solution, then aqueous ammonia at a concentration of 0.1 mol/L was slowly added dropwise to the solution until the solution was neutral, so that titanium oxysulfate was gradually and completely hydrolyzed to form a hydrated titanic acid precipitate. Subsequently, the hydrated titanic acid precipitate was ultrasonically dispersed, washed several times with deionized water, and separated by centrifugation. The separated hydrated titanic acid precipitate was ultrasonically dispersed in 150 ml of water, and 10 ml of 30% aqueous hydrogen peroxide solution was added under stirring to form a titanium-containing peroxo-complex solution. Subsequently, 1.6 g of sodium hydroxide was added to the peroxo-complex solution under stirring to form a pale yellow transparent solution. Then 40 ml of polyvinyl alcohol solution at a concentration of 10% was added to the above solution under stirring to form a precursor dispersion containing polyvinyl alcohol. Finally, the precursor dispersion containing polyvinyl alcohol was hydrothermally treated at 150 °C for 12 hours, to obtain sodium titanate microbead product having a hierarchical structure (the structure thereof is shown in <figref idref="f0003">FIG. 5</figref>).

Example 5

0048This Example provides a process for preparing sodium titanate having a hierarchical structure, which comprises the following steps: Under stirring, 2 g of titanium oxysulfate was dispersed and dissolved into 150 ml of water to form a solution, then aqueous ammonia at a concentration of 0.1 mol/L was slowly added dropwise to the solution until the solution was neutral, so that titanium oxysulfate was gradually and completely hydrolyzed to form a hydrated titanic acid precipitate. Subsequently, the hydrated titanic acid precipitate was ultrasonically dispersed, washed several times with deionized water, and separated by centrifugation. The separated hydrated titanic acid precipitate was ultrasonically dispersed in 150 ml of water, and 10 ml of 30% aqueous hydrogen peroxide solution was added under stirring to form a titanium-containing peroxo-complex solution. Subsequently, 1.6 g of sodium hydroxide was added to the peroxo-complex solution under stirring to form a pale yellow transparent solution. Then 40 ml of hydroxypropyl methyl cellulose solution at a concentration of 5% was added to the above solution under stirring to form a precursor dispersion containing hydroxypropyl methyl cellulose. Finally, the precursor dispersion containing hydroxypropyl methyl cellulose was hydrothermally treated at 150 °C for 12 hours, to obtain sodium titanate microbead product having a hierarchical structure (the structure thereof is shown in <figref idref="f0003">FIG. 6</figref>).

Example 6

0049This Example provides a process for preparing sodium titanate having a hierarchical structure, which comprises the following steps: Under stirring, 2 g of titanium oxysulfate was dispersed and dissolved into 150 ml of water to form a solution, then aqueous ammonia at a concentration of 0.1 mol/L was slowly added dropwise to the solution until the solution was neutral, so that titanium oxysulfate was gradually and completely hydrolyzed to form a hydrated titanic acid precipitate. Subsequently, the hydrated titanic acid precipitate was ultrasonically dispersed, washed several times with deionized water, and separated by centrifugation. The separated hydrated titanic acid precipitate was ultrasonically dispersed in 150 ml of water, and 10 ml of 30% aqueous hydrogen peroxide solution was added under stirring to form a titanium-containing peroxo-complex solution. Subsequently, 1.6 g of sodium hydroxide was added to the peroxo-complex solution under stirring to form a pale yellow transparent solution. Then 40 ml of polyethylene glycol (PEG-8000) solution at a concentration of 5% was added to the above solution under stirring to form a precursor dispersion containing polyethylene glycol. Finally, the precursor dispersion containing polyethylene glycol was hydrothermally treated at 150 °C for 12 hours, to obtain sodium titanate microbead product having a hierarchical structure (the structure thereof is shown in <figref idref="f0003">FIG. 7</figref>).

Example 7

0050This Example provides a process for preparing lithium titanate having a hierarchical structure, which comprises the following steps: Under stirring, 1.5 g of titanium isopropoxide was dispersed and dissolved into 150 ml of water for direct hydrolysis to form a hydrated titanic acid precipitate. Subsequently, the hydrated titanic acid precipitate was ultrasonically dispersed, washed several times with deionized water, and separated by centrifugation. The separated hydrated titanic acid precipitate was ultrasonically dispersed in 150 ml of water, and 10 ml of 30% aqueous hydrogen peroxide solution was added under stirring to form a titanium-containing peroxo-complex solution. Subsequently, 1.2 g of lithium hydroxide was added to the peroxo-complex solution under stirring to form a pale yellow transparent solution. Then 40 ml of polyvinyl alcohol solution at a concentration of 5% was added to the above solution under stirring to form a precursor dispersion containing polyvinyl alcohol. Finally, the precursor dispersion containing polyvinyl alcohol was hydrothermally treated at 150 °C for 12 hours, to obtain lithium titanate microbead product having a hierarchical structure (the structure thereof is shown in <figref idref="f0004">FIG. 8</figref>).

Example 8

0051This Example provides a process for preparing lithium titanate having a hierarchical structure, which comprises the following steps: Under stirring, 1.5 g of tetrabutyl titanate was dispersed and dissolved into 150 ml of water for direct hydrolysis to form a hydrated titanic acid precipitate. Subsequently, the hydrated titanic acid precipitate was ultrasonically dispersed, washed several times with deionized water, and separated by centrifugation. The separated hydrated titanic acid precipitate was ultrasonically dispersed in 150 ml of water, and 10 ml of 30% aqueous hydrogen peroxide solution was added under stirring to form a titanium-containing peroxo-complex solution. Subsequently, 1.6 g of lithium hydroxide was added to the peroxo-complex solution under stirring to form a pale yellow transparent solution. Then 40 ml of polyvinyl alcohol solution at a concentration of 5% was added to the above solution under stirring to form a precursor dispersion containing polyvinyl alcohol. Finally, the precursor dispersion containing polyvinyl alcohol was hydrothermally treated at 150 °C for 12 hours, to obtain lithium titanate microbead product having a hierarchical structure (the structure thereof is shown in <figref idref="f0004">FIG. 9</figref>).

Example 9

0052This Example provides a process for preparing potassium titanate having a hierarchical structure, which comprises the following steps: Under stirring, 3 g of titanium tetrachloride was dispersed and dissolved into 150 ml of water to form a solution, then potassium hydroxide at a concentration of 0.1 mol/L was slowly added dropwise to the solution until the solution was neutral, so that titanium tetrachloride was gradually and completely hydrolyzed to form a hydrated titanic acid precipitate. Subsequently, the hydrated titanic acid precipitate was ultrasonically dispersed, washed several times with deionized water, and separated by centrifugation. The separated hydrated titanic acid precipitate was ultrasonically dispersed in 150 ml of water, and 10 ml of 30% aqueous hydrogen peroxide solution was added under stirring to form a titanium-containing peroxo-complex solution. Subsequently, 1.7 g of potassium hydroxide was added to the peroxo-complex solution under stirring to form a pale yellow transparent solution. Then 40 ml of polyvinyl alcohol solution at a concentration of 5% was added to the above solution under stirring to form a precursor dispersion containing polyvinyl alcohol. Finally, the precursor dispersion containing polyvinyl alcohol was hydrothermally treated at 160 °C for 12 hours, to obtain potassium titanate microbead product having a hierarchical structure (the structure thereof is shown in <figref idref="f0004">FIG. 10</figref>).

Example 10

0053This example provides a process for preparing titanic acid having a hierarchical structure, which comprises the following steps: The sodium titanate microbead product having a hierarchical structure prepared in Example 1 was separated and dried in an oven. Subsequently, the dried sodium titanate microbead product having a hierarchical structure was washed several times with deionized water and separated, and then placed into a hydrochloric acid solution at 0.01 mol/L for hydrogen ion exchange. After hydrogen ion exchange, it was washed several times with deionized water until the pH of the washing liquid is close to neutral, and then separated and dried to obtain the titanic acid microbead product having a hierarchical structure.

Example 11

0054This example provides a process for preparing titanic acid having a hierarchical structure, which comprises the following steps: The sodium titanate microbead product having a hierarchical structure prepared in Example 1 was separated and dried in an oven. Subsequently, the dried sodium titanate microbead product having a hierarchical structure was washed several times with deionized water and separated, and then placed into a hydrochloric acid solution at 0.10 mol/L for hydrogen ion exchange. After hydrogen ion exchange, it was washed several times with deionized water until the pH of the washing liquid is close to neutral, and then separated and dried to obtain the titanic acid microbead product having a hierarchical structure.

Example 12

0055This example provides a process for preparing titanic acid having a hierarchical structure, which comprises the following steps: The titanic acid salt microbead product having a hierarchical structure prepared in any of Examples 2 to 9 was separated and dried in an oven. Subsequently, the dried titanic acid salt microbead product having a hierarchical structure was washed several times with deionized water and separated, and then placed into a hydrochloric acid solution at 0.05 mol/L for hydrogen ion exchange. After hydrogen ion exchange, it was washed several times with deionized water until the pH of the washing liquid is close to neutral, and then separated and dried to obtain the titanic acid microbead product having a hierarchical structure.

Example 13

0056This example provides a process for preparing titanium oxide having a hierarchical structure, which comprises the following steps: The titanic acid microbead product having a hierarchical structure prepared in Example 10 was placed in a muffle furnace and annealed at 600 °C for 3 hours, to obtain the titanium oxide microbead product having a hierarchical structure.

Example 14

0057This example provides a process for preparing titanium oxide having a hierarchical structure, which comprises the following steps: The titanic acid microbead product having a hierarchical structure prepared in Example 10 was dispersed into 50 ml of an aqueous nitric acid solution at 0.01 mol/L, and hydrothermally reacted at 120 °C for 6 hours, to obtain the titanium oxide microbead product having a hierarchical structure.

Example 15

0058This example provides a process for preparing titanium oxide having a hierarchical structure, which comprises the following steps: The titanic acid microbead product having a hierarchical structure prepared in Example 10 was dispersed into 50 ml of an aqueous hydrochloric acid solution at 0.005 mol/L, and hydrothermally reacted at 120 °C for 2 hours. Then the hydrothermal reaction product was separated, dried, and placed in a muffle furnace, and annealed at 400 °C for 4 hours, to obtain the titanium oxide microbead product having a hierarchical structure.

Example 16

0059This example provides a process for preparing titanium oxide having a hierarchical structure, which comprises the following steps: The titanic acid microbead product having a hierarchical structure prepared in any of Examples 11 to 12 was placed in a muffle furnace and annealed at 500 °C for 4 hours, to obtain the titanium oxide microbead product having a hierarchical structure.

Comparative Example 1

0060This Example provides a process for preparing sodium titanate having a hierarchical structure, which comprises the following steps: Under stirring, 2 g of titanium oxysulfate was dispersed and dissolved into 150 ml of water to form a solution, then aqueous ammonia at a concentration of 0.1 mol/L was slowly added dropwise to the solution until the solution was neutral, so that titanium oxysulfate was gradually and completely hydrolyzed to form a hydrated titanic acid precipitate. Subsequently, the hydrated titanic acid precipitate was ultrasonically dispersed, washed several times with deionized water, and separated by centrifugation. The separated hydrated titanic acid precipitate was ultrasonically dispersed in 190 ml of water, and 10 ml of 30% aqueous hydrogen peroxide solution was added under stirring to form a titanium-containing peroxo-complex solution. Subsequently, 1.6 g of sodium hydroxide was added to the peroxo-complex solution under stirring to form a pale yellow transparent solution. Finally, the pale yellow transparent solution was hydrothermally treated at 150 °C for 12 hours, to obtain sodium titanate microbead product having a hierarchical structure (the structure thereof is shown in <figref idref="f0005">FIG. 11</figref>).

Comparative Example 2

0061This Example provides a process for preparing lithium titanate having a hierarchical structure, which comprises the following steps: Under stirring, 1.5 g of titanium isopropoxide was dispersed and dissolved into 150 ml of water for direct hydrolysis to form a hydrated titanic acid precipitate. Subsequently, the hydrated titanic acid precipitate was ultrasonically dispersed, washed several times with deionized water, and separated by centrifugation. The separated hydrated titanic acid precipitate was ultrasonically dispersed in 150 ml of water, and 10 ml of 30% aqueous hydrogen peroxide solution was added under stirring to form a titanium-containing peroxo-complex solution. Subsequently, 1.2 g of lithium hydroxide was added to the peroxo-complex solution under stirring to form a pale yellow transparent solution. Finally, the pale yellow transparent solution was hydrothermally treated at 150 °C for 12 hours, to obtain lithium titanate microbead product having a hierarchical structure (the structure thereof is shown in <figref idref="f0005">FIG. 12</figref>).

Comparative Example 3

0062This Example provides a process for preparing potassium titanate having a hierarchical structure, which comprises the following steps: Under stirring, 3 g of titanium tetrachloride was dispersed and dissolved into 150 ml of water to form a solution, then potassium hydroxide at a concentration of 0.1 mol/L was slowly added dropwise to the solution until the solution was neutral, so that titanium tetrachloride was gradually and completely hydrolyzed to form a hydrated titanic acid precipitate. Subsequently, the hydrated titanic acid precipitate was ultrasonically dispersed, washed several times with deionized water, and separated by centrifugation. The separated hydrated titanic acid precipitate was ultrasonically dispersed in 150 ml of water, and 10 ml of 30% aqueous hydrogen peroxide solution was added under stirring to form a titanium-containing peroxo-complex solution. Subsequently, 1.7 g of potassium hydroxide was added to the peroxo-complex solution under stirring to form a pale yellow transparent solution. Finally, the pale yellow transparent solution was hydrothermally treated at 160 °C for 12 hours, to obtain potassium titanate microbead product having a hierarchical structure (the structure thereof is shown in <figref idref="f0005">FIG. 13</figref>).

0063The related data results of titanic acid salts in Examples 1-9 and Comparative Examples 1-3 are shown in Table 1 below. <tables id="tabl0001" num="0001"><table frame="all"><title>Table 1</title><tgroup cols="6"><colspec colnum="1" colname="col1" colwidth="26mm" /><colspec colnum="2" colname="col2" colwidth="21mm" /><colspec colnum="3" colname="col3" colwidth="47mm" /><colspec colnum="4" colname="col4" colwidth="22mm" /><colspec colnum="5" colname="col5" colwidth="28mm" /><colspec colnum="6" colname="col6" colwidth="25mm" /><thead><row><entry valign="middle">No.</entry><entry valign="middle">Titanic acid salt</entry><entry valign="middle">Additives and concentrations</entry><entry valign="middle">Constituent unit</entry><entry valign="middle">particle size of Microbead</entry><entry valign="middle">Dispersibility</entry></row></thead><tbody><row><entry valign="middle">Example 1</entry><entry valign="middle">Sodium titanate</entry><entry valign="middle">0.25% polyvinyl alcohol</entry><entry valign="middle">wire</entry><entry valign="middle">250-350nm</entry><entry valign="middle">OK</entry></row><row><entry valign="middle">Example 2</entry><entry valign="middle">Sodium titanate</entry><entry valign="middle">0.5% polyvinyl alcohol</entry><entry valign="middle">tube and wire</entry><entry valign="middle">150-250nm</entry><entry valign="middle">good</entry></row><row><entry valign="middle">Example 3</entry><entry valign="middle">Sodium titanate</entry><entry valign="middle">1.0% polyvinyl alcohol</entry><entry valign="middle">tube</entry><entry valign="middle">100-150nm</entry><entry valign="middle">good</entry></row><row><entry valign="middle">Example 4</entry><entry valign="middle">Sodium titanate</entry><entry valign="middle">2.0% polyvinyl alcohol</entry><entry valign="middle">tube</entry><entry valign="middle">80-100nm</entry><entry valign="middle">good</entry></row><row><entry valign="middle">Example 5</entry><entry valign="middle">Sodium titanate</entry><entry valign="middle">1.0% hydroxypropyl methylcellulose</entry><entry valign="middle">tube</entry><entry valign="middle">40-60nm</entry><entry valign="middle">good</entry></row><row><entry valign="middle">Example 6</entry><entry valign="middle">Sodium titanate</entry><entry valign="middle">1. 0% polyethylene glycol</entry><entry valign="middle">tube and platelet</entry><entry valign="middle">50-80nm</entry><entry valign="middle">OK</entry></row><row><entry valign="middle">Example 7</entry><entry valign="middle">Lithium titanate</entry><entry valign="middle">1.0% polyvinyl alcohol</entry><entry valign="middle">tube and platelet</entry><entry valign="middle">80-150nm</entry><entry valign="middle">OK</entry></row><row><entry valign="middle">Example 8</entry><entry valign="middle">Lithium titanate</entry><entry valign="middle">1.0% polyvinyl alcohol</entry><entry valign="middle">tube</entry><entry valign="middle">200-300nm</entry><entry valign="middle">OK</entry></row><row><entry valign="middle">Example 9</entry><entry valign="middle">Potassium titanate</entry><entry valign="middle">1.0% polyvinyl alcohol</entry><entry valign="middle">platelet</entry><entry valign="middle">60-80nm</entry><entry valign="middle">good</entry></row><row><entry valign="middle">Comparative example 1</entry><entry valign="middle">Sodium titanate</entry><entry valign="middle">none</entry><entry valign="middle">tube and wire</entry><entry valign="middle">300-600nm</entry><entry valign="middle">agglomerated</entry></row><row><entry valign="middle">Comparative example 2</entry><entry valign="middle">Lithium titanate</entry><entry valign="middle">none</entry><entry valign="middle">platelet</entry><entry valign="middle">300-700nm</entry><entry valign="middle">agglomerated</entry></row><row><entry valign="middle">Comparative example 3</entry><entry valign="middle">Potassium titanate</entry><entry valign="middle">none</entry><entry valign="middle">wire</entry><entry valign="middle">200-450nm</entry><entry valign="middle">agglomerated</entry></row></tbody></tgroup></table></tables>

0064It can be seen from the data of Table 1 that the results of constituent units, particle size of the microbead, and dispersability and the like in each of the products of the Examples are different, indicating that the process of the present invention can realize the control of the particle size of the titanic acid salts, and provide them with a hierarchical structure. Similarly, the process according to the present invention thus can realize the corresponding control of titanic acid and titanium oxide.

0065<figref idref="f0006">FIG. 14</figref> is a chart of discharge capacity of the sodium ion battery containing the sodium titanate microbead product having a hierarchical structure and different particle sizes obtained in Examples 1 to 4 and Comparative Example 1, at different charge/discharge rates. The discharge capacity was tested in the following manner. The sodium ion battery electrode was prepared using knife coating process. Firstly, a slurry was prepared in a mass ratio of sodium titanate microbead having a hierarchical structure: Super P: polyvinylidene fluoride (PVDF) = 7:2:1 with N-methylpyrrolidone (NMP) as solvent. Subsequently the slurry was uniformly coated on a copper foil using a knife coater, and then a model CR2032 button cell was assembled in a glove box with metallic lithium as a counter electrode, 1 mol/L NaClO₄ dissolved in EC/DMC (in volume ratio of 1:1) with a volume fraction of 2% of FEC additive as the electrolytic solution, and Glass Fiber as a separator and it was electrochemically tested. <figref idref="f0006">FIG. 15</figref> is a chart of discharge capacity of the sodium ion battery containing the lithium titanate microbead product having a hierarchical structure and different particle sizes obtained in Examples 8 to 9 and Comparative Example 2, at different charge/discharge rates. The discharge capacity was tested in the following manner. The lithium ion battery electrode was prepared using knife coating process . Firstly, a slurry was prepared in a mass ratio of lithium titanate microbead product having a hierarchical structure: Super P : polyvinylidene fluoride (PVDF) = 7:2:1 with N- methylpyrrolidone (NMP) as solvent. Subsequently the slurry was uniformly coated on a copper foil using a knife coater, and then a model CR2032 button cell was assembled in a glove box with metallic lithium as a counter electrode, 1 mol/L LiPF₆/EC-DMC-EMC (1:1:1) as the electrolytic solution, and Glass Fiber as a separator, and it was electrochemically tested. It can be seen by comparing data in <figref idref="f0006">FIGs. 14 and 15</figref> that the performance test results of the materials are closely related to the particle size of the materials. When sodium titanate is used in a sodium ion battery, the battery has the best discharge capacity at different charge/discharge rates when the particle size of sodium titanate having a hierarchical structure is 100-150 nm. When lithium titanate is used in a lithium ion battery, the battery has the best discharge capacity at different charge/discharge rates when the particle size of lithium titanate having a hierarchical structure is 60-80 nm.

0066In summary it can be seen that the process for preparing a titanic acid salt, titanic acid, and titanium oxide having a controllable particle size and a hierarchical structure provided by the present invention is the first to realize the particle size regulation of the material having a hierarchical structure. The process can also produce titanic acid salt microbeads with a hierarchical structure having a particle size of less than 100 nanometers, and obtain the morphology and structure when the material performance is the best.

0067It is to be understood that the above description is for the purpose of illustration and not limitation. Many embodiments and many applications other than the provided examples will be apparent to those skilled in the art by reading this description. Thus, the scope of the invention should not be determined by reference to the above description, but should be determined by the whole scope of the claims and equivalents to which these claims are entitled. The disclosures of all articles and references, including patent applications and publications, are hereby incorporated by reference in its entirety for all purposes. Any aspect of the subject matter disclosed herein, which is omitted in the claims, is not intended to be a disclaimer of the subject matter, and it should not be construed that the inventor does not consider such a subject matter as be a part of the disclosed inventive subject matters.