Preparation method of battery-grade nanometer titanium dioxide

Abstract

The application discloses a preparation method of battery-grade nanometer titanium dioxide, which comprises the following steps: dissolving a strong alkali weak acid salt as a pH regulator into ice water to make titanium salt completely hydrolyzed to prepare titanic acid; and using sodium hydroxide as the pH regulator to make the titanic acid further converted into a crystalline precursor to prepare a titanium complex [Ti(OH)4(OH)2] 0 Then, the complex is sheared and dispersed, and then subjected to a hydrothermal reaction; after the reaction is completed, the product is completely washed with water and calcined to prepare nanometer titanium dioxide. The prepared nanometer titanium dioxide has super-low impurity content, small particle size and uniform particle size distribution; the total content of magnetic substances, including Cr, Fe, Ni and Zn, is less than 0.2 ppm; the particle size is 0-100 nm; and the average particle size is 50 nm, so that the nanometer titanium dioxide is an excellent material for battery doping.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of titanium dioxide preparation, more particularly, to a preparation method of lithium iron phosphate-doped nano-titanium dioxide. TECHNICAL BACKGROUND

[0002] Titanium dioxide has been widely concerned in the fields of biological separation, sensor, energy storage, solar cell, photocatalysis and the like in recent years due to its high photocatalytic activity, low toxicity, low price, high chemical and optical stability. TiO2 has three crystal structures, namely, anatase, rutile and brookite. Brookite TiO2 belongs to the orthorhombic system and is a metastable state, and the current research is very little. Anatase and rutile TiO2 belong to the hexagonal system and have good heat resistance, thermal stability and chemical stability, among which anatase TiO2 shows high catalytic activity, high electrochemical activity and strong ultraviolet light absorption capacity, and has been widely used in environmental governance, photocatalysis, battery and the like. Currently, the preparation methods of anatase nano-titanium dioxide mainly include titanium tetrachloride gas phase oxidation method, liquid phase hydrolysis method of titanyl sulfate or titanium sulfate solution, sol-gel method and the like, and nano-titanium dioxide with uniform and small particle size can be prepared.

[0003] For example, Chinese patent CN1636880A discloses a method for preparing anatase nano-titanium dioxide, which is to prepare metatitanic acid suspension by adding water to a certain amount of metatitanic acid wet material, dropwise adding Na2CO3 aqueous solution thereto until the pH is 9-11, then adding carboxyl-containing organic matter (citric acid, oxalic acid, succinic acid, formic acid and the like) or glycerol as a modifier under stirring at 50-80℃ for aging, then washing the precipitate with distilled water until the conductivity of the filtrate is less than 20mS / m to obtain treated metatitanic acid solution, adding nitric acid and water thereto until the pH of the solution is 0.1, then aging at room temperature for 1h, and finally reacting the aged suspension at 130-160℃ for 10h to obtain anatase nano-titanium dioxide with small particle size and a particle size range of 15-110nm.

[0004] For example, Chinese patent CN109319833A discloses a preparation method of anatase mesoporous nanometer titanium dioxide, which mixes a titanium source (tetrabutyl titanate, etc.) with anhydrous ethanol to form solution A, and then mixes an amphiphilic eutectic solvent with anhydrous ethanol, adds deionized water and anhydrous acetic acid to form solution B; then mixes solution B and solution A, ages, and obtains nanometer titanium dioxide gel; washes and dries the nanometer titanium dioxide gel to obtain nanometer titanium dioxide particles; and finally grinds and calcines to obtain anatase mesoporous nanometer titanium dioxide. The method uses an amphiphilic eutectic solvent as a template agent for synthesizing anatase mesoporous nanometer titanium dioxide, promotes the formation of mesoporous nanometer titanium dioxide crystals, and the obtained nanometer titanium dioxide has uniform pore size, developed pore channels, and good crystallinity, but the addition of the template agent may cause certain cleaning difficulties.

[0005] For example, Chinese patent CN101497459A discloses a preparation method of nanometer anatase titanium dioxide powder, which rinses metatitanic acid with deionized water or distilled water several times to remove SO4 2- Then, an alkaline foaming agent (urea, ammonium carbonate, etc.) is added to the solution to adjust the pH value to 8.0-11.0, and a surface modifier (stearic acid, sodium silicate, etc.) is added, and the mixture is uniformly mixed to obtain a precursor. Finally, the precursor is placed in a reaction furnace and reacted at a temperature of 500-750°C for 2-3 hours to obtain anatase titanium dioxide powder with an average particle size of 20-80 nm and uniform particle size distribution. In this method, an alkaline foaming agent and a surface modifier are used, which have certain viscosity and are not easy to clean, and are easy to introduce impurities and agglomerate during calcination.

[0006] For example, Chinese patent CN1363521A discloses a preparation method of nanometer anatase titanium dioxide, which uses metatitanic acid as a raw material, adds an alkaline solution such as sodium carbonate and sodium bicarbonate for alkali dissolution, then filters and washes the alkali-dissolved substance to neutralization to obtain orthotitanic acid; then adds an acid solution for two times of acid dissolution to obtain a titanium dioxide sol; uses a coagulant to coagulate and squeeze the titanium dioxide sol, and uses an organic substance to extract and separate the titanium dioxide sol; then calcines and decomposes the organic substance at the decomposition temperature of the coagulant, cools to room temperature, and performs sand milling and air powdering to obtain nanometer anatase titanium dioxide powder. The titanium dioxide prepared by this method has a purity of more than 98% and a particle size of 5-30 nm. However, this method is complex and needs to go through the steps of alkali dissolution, two times of acid dissolution, coagulation, squeezing, organic substance extraction and separation, calcination, sand milling, and air powdering, and uses a sol-gel method, which increases the risk of impurity introduction and has high production cost.

[0007] For example, Chinese patent CN110342572A discloses a method for preparing anatase-type nano-titanium dioxide. The method is to dissolve tetrabutyl titanate in anhydrous ethanol to form a titanium alcohol solution under the conditions of ultrasonic oscillation, heating and high-speed mechanical stirring, then add the obtained titanium alcohol solution into an alkali solution; then move the obtained suspension into a reaction kettle for hydrothermal reaction; the obtained material is filtered, washed with acid and water, then refined, spray-dried and calcined to obtain anatase-type nano-titanium dioxide. The product prepared by the method has a mass fraction of titanium dioxide of more than 99%, uniform particle size, small particle size of 2-10 nm, good dispersibility and no agglomeration.

[0008] For example, Chinese patent CN109354062A discloses anatase-type nano-titanium dioxide and a preparation method and application thereof. The method specifically includes: adding pure water to TiCl4 to obtain a TiCl4 aqueous solution, then adding hydrochloric acid to the TiCl4 aqueous solution to prepare a TiCl4 acidolysis solution; adding sodium hydroxide to the acidolysis solution to neutralize the excess acid, and adding a precipitant (NaOH solution, ammonia water and NH4HCO3 solution) and a dispersant (PEG-2000 or ammonium polyacrylate) to perform a precipitation reaction, then filtering to obtain a precipitate and a filtrate, and washing the precipitate to neutral for standby; adding a dispersant to the precipitate and performing slurry preparation to obtain a slurry with a solid content of 30-50%, then performing sand milling and spray drying, then calcining at a temperature of 300-700°C for 60-150 min, and then performing airflow pulverization to obtain anatase-type nano-titanium dioxide with a pore size of less than 124A. The method adds a precipitant and an organic dispersant, the components are complex, and it is difficult to avoid impurity residues in the product.

[0009] Anatase-type nano-titanium dioxide has been widely used in the preparation of photocatalysis, solar cells, environmental purification, catalyst carriers, lithium batteries and gas sensors. In the above-mentioned prior art, anatase-type nano-titanium dioxide with small particle size or uniform particle size distribution can be obtained through a series of preparation methods, but none of the methods directly controls the particle size by forming a titanium complex aggregate and then using shear dispersion, and the prepared products are not mentioned for their impurity content. However, the nano-titanium dioxide on the market generally contains impurities such as iron oxide, aluminum oxide, copper, magnesium and zinc, and the impurity content is generally 0.01-0.5%. However, in the production process of lithium iron phosphate batteries, the anatase-type nano-titanium dioxide doped therein containing impurities, especially magnetic impurities, will adversely affect the electrochemical performance of the battery. In addition, poor uniformity of particle size distribution will cause uneven distribution of the doped titanium dioxide, affecting the doping effect and even reducing the electrochemical performance of the battery. Therefore, if the anatase-type nano-titanium dioxide doped in lithium iron phosphate has ultra-low impurity content and uniform particle size, the electrochemical performance of the battery and the chemical stability of the lithium iron phosphate crystal can be improved, thereby improving the energy density and cycle life of the battery. SUMMARY

[0010] The application provides a preparation method of battery-grade nanometer titanium dioxide. 0 The complex is sheared and dispersed, and then is subjected to hydrothermal reaction.

[0011] The application provides a preparation method of battery-grade nanometer titanium dioxide.

[0012] (1) a certain proportion of a strong base weak acid salt and water with a temperature of 0-5 DEG C is configured, and is placed in an ice water bath with a temperature of 0 DEG C, then a titanium salt is added dropwise to obtain a sponge-like titanium acid precipitate, wherein the metal ion in the strong base weak acid salt has a distinct flame color reaction phenomenon;

[0013] (2) the sponge-like titanium acid precipitate is centrifuged to obtain a centrifuged titanium acid precipitate;

[0014] (3) a strong base is added to the titanium acid precipitate, stirring and heating to a certain temperature, and keeping for a certain time to form a crystalline precursor titanium complex [Ti(OH)4(OH)2] 0 , wherein the metal ion in the strong base has a distinct flame color reaction phenomenon;

[0015] (4) the titanium complex [Ti(OH)4(OH)2] 0 is sheared and dispersed;

[0016] (5) the dispersed titanium complex [Ti(OH)4(OH)2] 0 is subjected to hydrothermal reaction to obtain small-particle-size suspended anatase titanium acid;

[0017] (6) the anatase titanium acid obtained in step (5) is repeatedly centrifuged and washed until the specific color of the metal ion in the flame color reaction disappears to obtain a centrifuged precipitate;

[0018] (7) the centrifuged precipitate obtained in step (6) is calcined at 500-800 DEG C for 3-5 h to obtain nanometer titanium dioxide.

[0019] The strong base weak acid salt includes sodium carbonate, potassium carbonate and the like, and preferably sodium carbonate.

[0020] The titanium salt includes titanium sulfate, titanium chloride and the like, preferably titanium chloride is selected. The titanium chloride is preferably prepared by chlorination method to obtain titanium chloride with less impurities, which can avoid more additional impurities pollution.

[0021] The strong base weak acid salt and water with temperature of 0-5℃ are configured in a certain proportion, and the mass ratio of the strong base weak acid salt to water is 1:10-4:10.

[0022] The strong base weak acid salt is dissolved in water with temperature of 0-5℃ to form a supersaturated solution, and the pH of the solution is 9-11, which also serves as a pH regulator. When the titanium salt is added for hydrolysis, the strong base weak acid salt is consumed by the acid generated by the hydrolysis reaction, and the undissolved strong base weak acid salt is dissolved to maintain the pH balance of the solution. After the titanium salt is completely added, the strong base weak acid salt is consumed, and the solution is strongly acidic. Finally, the titanium salt is completely hydrolyzed to obtain a titanium acid precipitate. In the reaction for preparing the titanium acid precipitate, the final solution is acidic, and the metal impurities such as Fe and Cr are in ionic state after reacting with the acid, so that most of the metal impurities can be removed by centrifugal separation.

[0023] The water with temperature of 0-5℃ is used to reduce the temperature of the reaction system and reduce the dissipation of volatile substances such as titanium tetrachloride during the addition of the titanium salt.

[0024] The mass ratio of the strong base weak acid salt to the titanium salt is 1:5-1:10.

[0025] The strong base weak acid salt is added to neutralize part of the acid generated during the hydrolysis, improve the hydrolysis rate, and preferably carbonate. When the carbonate is consumed, CO2 is generated, which avoids introducing new impurity anions. The mass ratio of the strong base weak acid salt to the titanium salt needs to be appropriate. Too little strong base weak acid salt will result in insufficient hydrolysis rate of the titanium salt, and too much strong base weak acid salt will introduce new impurity anions. 2-

[0026] The titanium salt is added to the strong base weak acid salt for 20-40 minutes. The speed of adding the titanium salt cannot be too fast. If the titanium salt is added too fast, the local pH of the solution will be too low, more CO2 will be generated, and the volatile titanium salt will be taken away, resulting in a decrease in yield.

[0027] The strong base includes sodium hydroxide, potassium hydroxide and the like, and sodium hydroxide is preferably selected.

[0028] The strong base is added to the titanium acid precipitate for stirring and heating to 40-45℃, and the temperature is maintained for 100-150 minutes. The stirring speed is 300-800 r / min, and a titanium complex [Ti(OH)4(OH)2] 0 is formed.

[0029] The mass ratio of the strong base to the titanium salt is 1:1.5-1:3.​

[0030] Strong base is added as pH regulator into the precipitate of titanic acid, so that the pH of the solution is 5-6, and the precipitate of titanic acid is further converted into crystalline precursor, so that it forms titanium complex [Ti(OH)4(OH)2] 0 , wherein the temperature needs to be raised to 40-45℃, and the temperature needs to be kept for 100-150 min, so that the titanium complex [Ti(OH)4(OH)2] 0 precursor is formed; wherein at the temperature of 40-45℃, part of the precursor forms crystallization center, i.e. crystal nucleus, through hydroxyl bridging and oxyl bridging, the number of crystal nucleus is controlled by controlling the holding time, so as to avoid the growth of crystal, and the size of crystal is controlled and the formation of spherical crystal is promoted by controlling the stirring speed, too fast stirring will lead to too fast growth of crystal, so that the crystal particle is too large, and too slow stirring will lead to slow growth of crystal, so that the crystal particle is too small.

[0031] In addition, the mass ratio of strong base and titanium salt also needs to be appropriate, by controlling the pH of the solution, the conversion of titanic acid to form more [Ti(OH)4(OH)2] 0 precursor, and further form more crystal nucleus with anatase structure, which is beneficial to reduce the particle size of crystal. When the content of alkali in the solution is small and the pH is low, rutile structure crystal nucleus will appear, and the grain size of rutile phase will be slightly larger than that of anatase.

[0032] Among them, the strong base weak acid salt and strong base containing the same metal ion are preferred, such as sodium carbonate and sodium hydroxide. The metal ion contained in the selected strong base weak acid salt and strong base has obvious flame color reaction phenomenon, which is to take the disappearance of the characteristic color of metal ion in the flame color reaction as the end point of water washing in the subsequent repeated centrifugal water washing to remove soluble impurities in the precipitate of titanic acid. The flame color reaction detection of metal ion in the water washing liquid is to burn the water washing liquid and observe the color of the flame, when the characteristic color of metal ion in the flame color reaction disappears, it means that the soluble metal ion in the solution is basically removed. And the same kind of metal ion is used in the strong base weak acid salt and strong base, so as to avoid the introduction of multiple metal impurities, and the yellow color of Na + in the flame color reaction can be used as the end point of water washing, which is convenient for confirming the end point of water washing.

[0033] Among them, the disperser is selected to form titanium complex [Ti(OH)4(OH)2] 0The agglomerates are sheared and dispersed, preferably using a high-speed disc disperser, at a rotational speed of 5000-20000r / min, and for 10-20min. The shearing operation breaks and re-creates the different crystal nuclei produced in the previous step, with the aim of forming crystal nuclei of uniform morphology, which is crucial for obtaining hydrolysis products of uniform particle size. Too high a rotational speed will result in crystal nuclei that are too small, causing the crystals to grow too quickly during the subsequent hydrothermal reaction, and resulting in products of large particle size. Too low a rotational speed will result in crystal nuclei that are too large, also resulting in products of large particle size.

[0034] The hydrothermal reaction is carried out at a temperature of 110-150℃, a pressure of 1.5-8.0bar, for 360-720min, and at a stirring speed of 0-500r / min.

[0035] The water used in the method is laboratory grade secondary water. The use of laboratory grade secondary water reduces the pollution caused by impurities in the water.

[0036] The present application controls the particle size of the product by adding a strong base to the titanium acid precipitate to form a titanium complex [Ti(OH)4(OH)2] 0 The titanium complex [Ti(OH)4(OH)2] 0 is then sheared and dispersed to control the particle size of the product, making the particle size uniform, and the solution after the reaction to form titanium acid is acidic, causing the metal impurities such as Fe and Cr to be in ionic form, which can be removed by centrifugation. The metal cations in the subsequently added strong base and weak acid salt and strong base are easily dissolved, and the subsequent water washing is easy to remove, while the anions are completely consumed, avoiding the introduction of more impurities. Therefore, the nano-titanium dioxide prepared by the present application has a very low impurity content, the total content of magnetic substances including Cr, Fe, Ni and Zn is less than 0.2ppm, the product is spherical, the particle size is 0-100nm, and the particle size distribution is uniform, with an average particle size of 50nm, meeting the requirements of battery-grade nano-titanium dioxide. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 Process flow chart for nano-titanium dioxide

[0038] Figure 2 XRD pattern of Example 1

[0039] Figure 3 XRD pattern of Example 2

[0040] Figure 4 XRD pattern of Example 3

[0041] Figure 5 XRD pattern of Example 4

[0042] Figure 6XRD pattern of Example 5

[0043] Figure 7 SEM pattern of Example 1

[0044] Figure 8 SEM pattern of Example 2

[0045] Figure 9 SEM pattern of Example 3

[0046] Figure 10 SEM pattern of Example 4

[0047] Figure 11 SEM pattern of Example 5 DETAILED DESCRIPTION

[0048] Embodiments of the present application will be described in more detail below. The present application can be implemented in various forms and should not be construed as being limited to the embodiments set forth herein; rather, these embodiments are provided so that the present application will be thorough and complete, and will fully convey the scope of the application to those skilled in the art. It should be understood that the embodiments of the present application are only for illustrative purposes and are not intended to limit the scope of the present application.

[0049] The term "comprising" as used herein is an open term that is intended to mean "including, but not limited to." The term "based on" is intended to mean "based, at least in part, on" The term "one embodiment" is intended to mean "at least one embodiment." The term "another embodiment" is intended to mean "at least one additional embodiment." Relative terms such as "first," "second," "third," and the like are intended to convey the relative position of the elements in the description and are not intended to convey any specific order or sequence of implementation.

[0050] All embodiments of the present application are implemented in the following technical solutions, and the flow chart is shown in FIG. 1. Figure 1 The specific steps include:

[0051] (1) A solution is prepared according to a mass ratio of sodium carbonate to water of 1:10 to 4:10, the water temperature is 5°C, and the solution is placed in a four-necked flask, then an ice water pot at 0°C is placed therein, and then titanium tetrachloride is slowly added dropwise, the dropwise adding time is 30 min, and a sponge-like titanic acid precipitate is obtained, wherein the mass ratio of sodium carbonate to titanium tetrachloride is 1:5 to 1:10;

[0052] (2) The sponge-like titanic acid precipitate is centrifuged to obtain a centrifuged titanic acid precipitate;

[0053] (3) The titanic acid precipitate is placed in a four-necked flask, sodium hydroxide is added, and the temperature is raised to 40-45°C, and the temperature is maintained for 100-150 min, the stirring speed is 300-800 r / min, and a titanium complex [Ti(OH)4(OH)2] is formed 0 , wherein the mass ratio of the strong base to the titanium salt is 1:1.5 to 1:3;

[0054] (4) Shearing dispersion of the titanium complex [Ti(OH)4(OH)2] with a disperser, the rotating speed is set at 5000-20000 r / min, and the shearing time is 10-20 min; 0

[0055] (5) The colloid is transferred into a hydrothermal reactor, and heated to 110-150°C, the pressure is 1.5-8.0 bar, the holding time is 360-720 min, and the stirring speed is 0-500 r / min, to obtain the octahedral molecular small-particle-size suspended anatase titanium oxide;

[0056] (6) The anatase titanium oxide obtained in step (5) is repeatedly centrifuged and washed with water until the flame color reaction yellow disappears in the washing liquid, to obtain the centrifuged precipitate;

[0057] (7) The centrifuged precipitate is placed into a tube furnace and calcined at 500-800°C for 3-5 h to remove free water and bound water, to obtain the battery-grade nanometer titanium dioxide.

[0058] The specific implementation conditions of different examples are shown in Table 1:

[0059] Table 1 Specific conditions of different examples

[0060]

[0061] The nanometer titanium dioxide prepared in Examples 1-5 in Table 1 is subjected to XRD, SEM, ICP and particle size distribution tests, and the results are as follows:

[0062] (1) The XRD of Examples 1-5 is shown in the attached Figures 2 to 6 figure, all samples have a sharp diffraction peak at 25.5°, which is the characteristic peak of anatase titanium dioxide, indicating that the sample is anatase titanium dioxide, and the intensity of the characteristic peak is high, indicating that the sample has high crystallinity, which meets the requirements of battery-grade nanometer titanium dioxide. Among them, Example 3 has a small peak at 27°, which is the characteristic peak of rutile titanium dioxide, because the mass ratio of sodium hydroxide to titanium tetrachloride in Example 2 is 1:3, and the amount of alkali added is less, resulting in a lower pH of the solution, so a small amount of rutile phase appears, but the main phase is still anatase, and the corresponding, from the particle size distribution test results in Table 3, it can also be seen that Example 2 has a slightly larger particle size than Examples 1 and 2 because of the doping of a small amount of rutile phase.

[0063] (2) The SEM of Examples 1-5 is shown in the attached Figures 7 to 11 ​As shown in the SEM, all the samples are spherical, wherein the particle size of the samples of Examples 1-3 is about 0-100 nm, and the particle size is relatively uniform, the particle size distribution of the obtained samples is uniform, and Examples 4 and 5 are comparative examples with shearing dispersion rotation speed out of the range, and the formed sample particles are larger, as shown in the attached Figure 10 and the attached Figure 11 As shown in the SEM, all the samples are spherical, wherein the particle size of the samples of Examples 1-3 is about 0-100 nm, and the particle size is relatively uniform, the particle size distribution of the obtained samples is uniform, and Examples 4 and 5 are comparative examples with shearing dispersion rotation speed out of the range, and the formed sample particles are larger, as shown in the attached

[0064] (3) The ICP test results of Examples 1-5 are shown in Table 2, and the ICP test results show that the total content of the magnetic substances including Cr, Fe, Ni and Zn in the sample is 0.15-0.2 ppm, the magnetic substance of the sample is less, and it is proved that the prepared nano titanium dioxide has ultra-low impurity content, which has a great advantage for battery doping.

[0065] (4) The particle size distribution test results of Examples 1-5 are shown in Table 3, and the particle size distribution test results show that the average particle size of the samples of Examples 1-3 is 40-50 nm, the overall particle size is less than 100 nm, and the overall average particle size is 50 nm; Example 4 forms a smaller crystal nucleus because the shearing speed is too large, and larger particles are formed during hydrothermal reaction, with an average particle size of 82.18 nm and a maximum particle size of 334 nm; Example 5 forms a larger crystal nucleus because the shearing speed is too small, and larger particles are also formed during hydrothermal reaction, with an average particle size of 136.94 nm and a maximum particle size of 490.84 nm; it is shown that the particle size and uniform distribution of the product can be effectively controlled by shearing dispersion of the complex.

[0066] Table 2 ICP test results

[0067]

[0068] Table 3 Particle size distribution test results

[0069]

[0070]

[0071] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of changes or replacements within the technical range disclosed in the present application, which should be covered within the protection scope of the present application, therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for producing a battery-grade nanoscale titanium dioxide, characterized by, Prepared by the following method, the specific steps include: (1) configuring the strong base weak acid salt and water with a temperature of 0-5℃ according to a certain proportion, placing in the ice water bath of 0℃, then adding the titanium salt dropwise to obtain the sponge-like titanium acid precipitate, wherein the metal ion in the strong base weak acid salt has obvious flame color reaction phenomenon; (2) centrifugal separation of the sponge-like titanium acid precipitate to obtain the centrifuged titanium acid precipitate; (3) adding a strong base into the titanium acid precipitate, stirring and heating to a certain temperature, and keeping for a certain time to form a crystalline precursor titanium complex [Ti(OH)4(OH)2] 0 wherein the metal ion in the strong base has a distinct flame color reaction phenomenon; (4) the titanium complex [Ti(OH)4(OH)2] 0 shear dispersion of the agglomerates; (5) the dispersed titanium complex [Ti(OH)4(OH)2] 0 hydrothermal reaction to obtain small-particle-size suspended anatase phase titanic acid; (6) repeating the centrifugal separation and water washing of the anatase titanium acid obtained in step (5) until the specific color of the metal ion in the water washing liquid disappears in the flame color reaction, to obtain the centrifuged precipitate; (7) calcining the centrifuged precipitate obtained in step (6) at 500-800℃ for 3-5h to obtain the nano titanium dioxide.

2. The method for preparing battery-grade nano-titanium dioxide according to claim 1, characterized in that, The strong base weak acid salt is sodium carbonate or potassium carbonate.

3. The method for preparing battery-grade nano-titanium dioxide according to claim 1, characterized in that, The strong base weak acid salt is sodium carbonate.

4. The method for preparing battery-grade nano-titanium dioxide according to claim 1, characterized in that, The titanium salt is titanium sulfate or titanium chloride.

5. The method for preparing battery-grade nano-titanium dioxide according to claim 1, characterized in that, The titanium salt is titanium chloride.

6. The method for preparing battery-grade nano-titanium dioxide according to claim 1, characterized in that, The strong base weak acid salt and water with a temperature of 0-5℃ are configured according to a certain proportion, and the mass ratio of the strong base weak acid salt to water is 1:10-4:

10.

7. The method for preparing battery-grade nano-titanium dioxide according to claim 1, characterized in that, The mass ratio of the strong base weak acid salt to the titanium salt is 1:5-1:

10.

8. The method of claim 1, wherein the battery grade nanoscale titanium dioxide is prepared by the process of claim 1, wherein the titanium dioxide has a particle size of 20-50 nm, a specific surface area of 100-200 m2 / g, and a purity of 99.9% or more. The titanium salt is added to the strong base weak acid salt for 20-40min.

9. The method for preparing battery-grade nano-titanium dioxide according to claim 1, characterized in that, The strong base is sodium hydroxide or potassium hydroxide.

10. The method for preparing battery-grade nano-titanium dioxide according to claim 1, characterized in that, The strong base is sodium hydroxide.

11. The method for preparing battery-grade nano-titanium dioxide according to claim 1, characterized in that, The strong base is added to the titanium acid precipitate, stirred and heated to 40-45°C, and kept for 100-150 min, with stirring speed of 300-800 r / min, to form titanium complex [Ti(OH)4(OH)2] 0 .

12. The method of claim 1, wherein the battery grade nanoscale titanium dioxide is characterized by: The mass ratio of the strong base to the titanium salt is 1:1.5-1:

3.

13. The method of claim 1, wherein the battery grade nanoscale titanium dioxide is prepared by the process of claim 1, wherein the titanium dioxide has a particle size of 20-50 nm, a specific surface area of 100-200 m2 / g, and a purity of 99.9% or more. The strong base weak acid salt and the strong base containing the same kind of metal ion are selected.

14. The method for preparing battery-grade nano-titanium dioxide according to claim 1, characterized in that, The strong base weak acid salt and the strong base are sodium carbonate and sodium hydroxide.

15. The method for preparing battery-grade nano-titanium dioxide according to claim 1, characterized in that, The titanium complex is sheared and dispersed by using a dispersing machine, and the rotating speed is set to 5000-20000r / min, and the shearing time is 10-20min.

16. The method of claim 1, wherein the battery grade nanoscale titanium dioxide is characterized by: The titanium complex is sheared and dispersed by using a high-speed disc dispersing machine, and the rotating speed is set to 5000-20000r / min, and the shearing time is 10-20min.

17. The method for preparing battery-grade nano-titanium dioxide according to claim 1, characterized in that, The temperature of the hydrothermal reaction is 110-150℃, the pressure is 1.5-8.0bar, the holding time is 360-720min, and the stirring speed is 0-500r / min.

18. The method for preparing battery-grade nano-titanium dioxide according to claim 1, characterized in that, The water used in the method is laboratory secondary water.

19. The method for preparing battery-grade nano-titanium dioxide according to claim 1, characterized in that, The content of the magnetic substance in the prepared nano titanium dioxide is less than 0.2ppm, the particle size is 0-100nm, and the average particle size is 50nm.

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