Preparation method of rice-shaped TiO2-B with adjustable length-diameter ratio

Abstract

This invention provides a method for preparing rice-grain-shaped TiO2-B with adjustable aspect ratio, belonging to the technical field of anode materials for alkali metal ion batteries. The TiO2-B belongs to the monoclinic crystal system, space group C2 / m. The TiO2-B particles are ellipsoidal, with the c-axis as the major axis (7-13 nm) and the ab-axis as the minor axis. Its aspect ratio can be controlled within the range of 1.76-3.51, achieving a purity greater than 98%. The raw materials are inexpensive and reusable. The preparation method provided by this invention is simple, yields a highly controllable product with a large specific surface area, high purity, and good electrochemical performance.

Description

Technical Field

[0001] This invention belongs to the technical field of alkali metal ion battery anode materials, specifically relating to a method for preparing rice-grain-shaped TiO2-B, and the ability to control the aspect ratio of its particles. Background Technology

[0002] The rapid development of power batteries requires alkali metal ion batteries (lithium-ion batteries, sodium-ion batteries, potassium-ion batteries, etc.) to have better energy density, fast charging performance, and cycle performance.

[0003] TiO2-B, as an oxide anode material for lithium-ion batteries, possesses a theoretical capacity of 335 mAh / g, a rapid lithium-ion diffusion channel along the b-axis, and a low lithium intercalation volume expansion rate. This gives TiO2-B superior rate performance and cycle stability compared to other anode materials (including graphite, silicon, and other TiO2 materials). The lithium intercalation process in TiO2-B involves multiple intercalation sites and pathways, making lithium-ion diffusion in TiO2-B significantly constrained by particle morphology, particularly by the size of the directions related to the lithium intercalation pathway.

[0004] Several patents have disclosed methods for controlling the particle morphology of TiO2-B during preparation. Chinese patent CN108598455B discloses a method for preparing hierarchical TiO2-B using ammonium fluorotitanate and boric acid. The synthesized TiO2-B has exposed {010} crystal planes, which is considered beneficial for lithium-ion intercalation. However, the synthesized product contains obvious rutile impurities, resulting in poor cycling performance. Chinese patent CN113511674B reports a method for synthesizing ultralong TiO2-B nanotubes from anatase in a high-concentration NaOH solution. This TiO2-B exhibits a distinct nanotube structure and hollow cavities, which is considered beneficial for improving rate performance. However, the high concentration of NaOH, excessively long hydrothermal time, and acid replacement time increase the cost and resource consumption of the synthesis process. A US patent reports a method for preparing TiO2-B mesoporous spheres by spray pyrolysis granulation followed by NaOH etching of a template. Mesoporous structures are considered beneficial for electrolyte penetration and lithium-ion intercalation; however, the synthetic method is cumbersome and involves anatase formation. In summary, currently reported synthetic methods for controlling morphology often involve complex synthetic steps, are accompanied by the formation of impurity phases, and have uncontrollable morphology. Summary of the Invention

[0005] The technical problem to be solved by this invention is to overcome the shortcomings and defects mentioned in the background art. This invention utilizes the difference in adsorption energy of glycolic acid on different crystal nuclei surfaces of TiO2-B to synthesize precursor nanoparticles with

[001] orientation. Furthermore, the degree of directional adhesion can be controlled by adjusting the concentration of glycolic acid, and the degree of Oswald ripening can be adjusted by controlling the calcination temperature, thereby achieving control over the aspect ratio of TiO2-B particles within the range of 1.76-3.51. The preparation method of this invention is simple, low-cost, and produces products with high purity, strong controllability, and excellent performance.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for preparing rice-grain-shaped TiO2-B with adjustable aspect ratio specifically includes the following steps:

[0008] (1) Add the titanium source to dilute sulfuric acid, then add glycolic acid and stir to obtain precursor solution A;

[0009] (2) Precursor solution A is subjected to hydrothermal reaction to obtain precursor crystal nuclei with a certain

[001] orientation and unnucleated amorphous material;

[0010] (3) Secondary hydrothermal treatment causes the precursor nuclei obtained in step (2) to continue to attach along the

[001] direction and absorb amorphous material to form a rice-grain-shaped precursor.

[0011] (4) Calcine the rice-grain-shaped precursor obtained in step (3) in air.

[0012] In step (1), the concentration of dilute sulfuric acid is 0.1-0.15 mol / L, the mass ratio of titanium source to dilute sulfuric acid is 0.015-0.05, and the concentration of glycolic acid after dissolution is 1-1.5 mol / L.

[0013] In step (1), the titanium source includes any one or more of tetrabutyl titanate, tetraethyl titanate, isopropyl titanate, tetraisobutyl titanate, and di(triethanolamine) titanate diisopropyl.

[0014] In step (1), the glycolic acid solution is added after it changes from turbid to clear and transparent and has no odor and volatilizes, so as to co-evaporate the titanium source and hydrolyze it to obtain fusel oil;

[0015] The raw materials mentioned in step (1), except for the titanium source, can be reused and will not reduce the purity of TiO2-B.

[0016] In step (2), the hydrothermal reaction temperature is 180℃ and the time is 30 minutes;

[0017] In step (3), the secondary hydrothermal reaction temperature is 140-150℃ and the time is 6-12 hours;

[0018] In step (4), the calcination temperature range is 370-500℃, and the heating rate is 2-5℃ / min;

[0019] The present invention also relates to rice-grain-shaped TiO2-B with adjustable aspect ratio prepared according to the above method.

[0020] The special features of this invention are:

[0021] In step (1), the concentration of glycolic acid is controlled to determine the degree of directional adhesion in step (2). A high concentration of glycolic acid helps to increase the aspect ratio of the particles. In step (2), the calcination temperature range is 370-500℃, and the heating rate is 2-5℃ / min. The calcination temperature affects the degree of ripening of TiO2-B. A high calcination temperature helps to reduce the aspect ratio of the particles.

[0022] In step (2), the temperature and time of hydrothermal treatment should be accurately controlled at 180°C for 30 minutes to maintain a suitable ratio of precursor nuclei and unnucleated amorphous material.

[0023] In step (1), glycolic acid is added only after the butanol produced by the hydrolysis of tetrabutyl titanate and sulfuric acid has fully volatilized, thereby reducing the rutile impurity phase induced by butanol and improving the purity of TiO2-B. All raw materials mentioned in step (1), except for the titanium source, can be reused without reducing the purity of TiO2-B.

[0024] The rice-grain-shaped TiO2-B prepared by this method has many advantages, such as high phase purity, high specific surface area, and excellent electrochemical performance. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 The X-ray diffraction (XRD) pattern and high-resolution transmission electron microscope (HRTEM) image of the product after hydrothermal treatment at 180°C for 30 minutes are shown in Example 1 of this invention.

[0027] Figure 2 The images are XRD patterns of the products of Example 1 and Comparative Example 1 of this invention.

[0028] Figure 3 These are HRTEM images of the products of Example 1 and Comparative Example 1 of the present invention.

[0029] Figure 4The graphs show the electrochemical performance of the products of Example 1 and Comparative Example 1 in a lithium-ion half-cell.

[0030] Figure 5 The XRD patterns of TiO2-B with different aspect ratios obtained by adjusting the glycolic acid concentration in Examples 1-3 of this invention are shown.

[0031] Figure 6 This is a synchrotron radiation XRD pattern of the precursor under in-situ heating in Embodiment 1 of the present invention.

[0032] Figure 7 The XRD patterns of TiO2-B with different aspect ratios were obtained by adjusting the glycolic acid concentration and increasing the calcination temperature to 430°C in Examples 4, 5, and 6 of this invention.

[0033] Figure 8 These are the dQ / dV fitting curves of the products from Examples 1, 7, and Comparative Example 2 of this invention. Detailed Implementation

[0034] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0035] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention. The preferred embodiments and materials described herein are for illustrative purposes only, and various modifications and refinements can be made without departing from the principles of the embodiments of the invention; such modifications and refinements are also considered to be within the scope of the invention.

[0036] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0037] Example 1

[0038] A rice-grain-shaped TiO2-B is prepared by the following steps:

[0039] (1) Dissolve 1 ml of tetrabutyl titanate in 30 ml of 0.12 mol / L dilute sulfuric acid. Stir thoroughly until the solution becomes clear and no odor evaporates. Add 3.5 g of glycolic acid and continue stirring. Add deionized water to restore the solution to 30 ml. Transfer the stirred solution to a 50 ml Teflon hydrothermal reactor and heat to 180 °C for 30 minutes. Then cool to 140 °C and continue heating for 6 hours. After filtration / centrifugation and washing, the precursor is obtained.

[0040] (2) After the precursor is dried, it is placed in a muffle furnace and heated to 370°C for 2 hours. It is then cooled with the furnace. The calcination atmosphere is air, and the heating rate is 2°C per minute. The powder is then removed, crushed, and ground evenly to obtain rice-grain-shaped TiO2-B.

[0041] Comparative Example 1

[0042] A rice-grain-shaped TiO2-B is prepared in the same way as in Example 1, except that the hydrothermal process in step (1) is changed to be maintained at 160°C for 4 hours.

[0043] Table 1: Calculation and statistical analysis of the ab plane, c-axis dimensions, and aspect ratio of TiO2-B in Example 1 and Comparative Example 1 using the Williamson-Hall (WH) method and HRTEM, respectively.

[0044]

[0045] The TiO2-B prepared in Example 1 and Comparative Example 1 were analyzed by XRD and HRTEM. The particle size was characterized using the Scherrer equation and HRTEM. Figure 1 As shown, the product obtained after hydrothermal treatment at 180°C for 30 minutes in Example 1 consists of 3-5 nanometer particles and unnucleated amorphous materials, which is a prerequisite for subsequent directional adhesion. The XRD and TEM results of the final products of Example 1 and Comparative Example 1 are shown below. Figure 2 , 3 As shown in Table 1, the rice-grain-shaped TiO2-B exhibits a higher (002) / (110) peak intensity ratio, indicating that the rice-grain-shaped TiO2-B possesses a certain c-axis preferred orientation. In HRTEM, the c-axis of the rice-grain-shaped TiO2-B is the long axis, approximately 10 nm, while the ab-axis is the short axis, approximately 4 nm. The final product of Comparative Example 1 is spherical. In terms of electrochemical performance, the rice-grain-shaped TiO2-B exhibits better cycling performance at high rates, with a capacity retention of 93.67% after 5000 cycles at 10C, compared to only 75.54% in Comparative Example 1.

[0046] Example 2

[0047] A rice-grain-shaped TiO2-B is prepared in the same way as in Example 1, except that the amount of glycolic acid added in step (1) is 3g.

[0048] Example 3

[0049] A rice-grain-shaped TiO2-B is prepared in the same way as in Example 1, except that the amount of glycolic acid added in step (1) is 2.5g.

[0050] Table 2: Full width at half maximum (FWHM) of the

[110] and

[002] crystal planes in the fitted XRD images of Examples 1-6, and aspect ratios calculated using the Scherer formula.

[0051]

[110] FWHM

[002] FWHM Axial Ratio (AR) Example 1 2.381 0.702 3.51 Example 2 2.446 0.745 3.32 Example 3 2.175 1.104 2.04 Example 4 1.553 0.681 2.36 Example 5 1.610 0.818 2.02 Example 6 1.634 0.961 1.76

[0052] The TiO2-B prepared in Examples 1-3 were subjected to XRD analysis. Figure 4 As shown in Table 2, the peak intensity ratio of (002) and (110) gradually decreases as the amount of glycolic acid decreases. This indicates that the decrease in glycolic acid concentration during hydrothermal process reduces the degree of directional adhesion, thereby reducing the aspect ratio of TiO2-B.

[0053] Example 4

[0054] A rice-grain-shaped TiO2-B is prepared in the same way as in Example 1, except that the calcination temperature in step (2) is 430℃.

[0055] Example 5

[0056] A rice-grain-shaped TiO2-B is prepared in the same way as in Example 2, except that the calcination temperature in step (2) is 430℃.

[0057] Example 6

[0058] A rice-grain-shaped TiO2-B is prepared in the same way as in Example 3, except that the calcination temperature in step (2) is 430℃.

[0059] The TiO2-B prepared in Examples 4-6 were subjected to XRD analysis. Figure 5 As shown in Table 2, the rice-grain-shaped precursor obtained in Example 1 exhibited a decrease in the half-width and an increase in the peak intensity of the (100), (110), and (020) crystal planes during the heating process to 500℃. This indicates that the rice-grain-shaped precursor underwent ripening along the ab-axis during the heating process, which caused the rice-grain-shaped precursor to transition to a spherical shape. During this process, the aspect ratio of the ellipsoid gradually decreased. Therefore, in Examples 4-6, by using different concentrations of glycolic acid to control the aspect ratio, controlling the temperature of the calcination process can further regulate the aspect ratio of the rice-grain TiO2-B.

[0060] Example 7

[0061] A rice-grain-shaped TiO2-B is prepared in the same way as in Example 1, except that the supernatant from step (1) of Example 4 is taken and added to the solution after evaporation in step (1) of Example 1.

[0062] Comparative Example 2

[0063] A rice-grain-shaped TiO2-B is prepared in the same way as in Example 1, except that in step (1), glycolic acid is added first and then tetrabutyl titanate is added, and the mixture is sealed during stirring to prevent the solution from evaporating.

[0064] Table 3: dQ / dV peak area ratio of products from Examples 1, 7, and Comparative Example 2 (A) x / (A x +A y The fitted values ​​and the content values ​​calculated using the method described in patent CN113030061B

[0065]

[0066]

[0067] The TiO2-B prepared in Examples 1, 7, and Comparative Example 2 were analyzed for dQ / dV. Figure 8 As shown, the TiO2-B prepared in Examples 1 and 7 both have a purity greater than 98%, indicating that the sulfuric acid used to regulate pH and the glycolic acid used to control nucleation are not significantly consumed. This allows for the reuse of raw materials other than the titanium source during the synthesis process, reducing synthesis costs. The TiO2-B prepared in Comparative Example 2 has a purity of 94.95%, indicating that adding the titanium source first and evaporating the fusel oil produced by hydrolysis helps improve product purity.

[0068] In summary, this invention controls the anisotropy during nucleation and directional attachment by regulating the ligand concentration during the hydrothermal process in material synthesis, thereby preferentially growing nanocrystal nuclei along the

[001] direction and controlling the aspect ratio of ellipsoidal nanoparticles. Furthermore, strict control of the calcination temperature can further regulate the aspect ratio, resulting in rice-grain-type TiO2-B with excellent electrochemical performance. This method, based solely on thermodynamics, allows for arbitrary control of the ellipsoidal aspect ratio within a certain range without increasing experimental costs. This method is simple to operate, low in cost, high in purity, highly reproducible, and offers strong product controllability.

[0069] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Therefore, any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention should fall within the protection scope of the present invention.

Claims

1. A method for preparing rice-grain-shaped TiO2-B with adjustable aspect ratio, characterized in that, Rice-grain-sized TiO2-B belongs to the monoclinic crystal system, space group C2 / m. The TiO2-B particles are ellipsoidal, with the c-axis being the major axis (7-13 nm) and the ab-axis being the minor axis. Its aspect ratio can be controlled within the range of 1.76-3.51, and the synthesis purity is above 98%. The method for preparing rice-grain-sized TiO2-B with controllable aspect ratio includes the following steps: S1. Preparation of precursor solution: Add titanium source to dilute sulfuric acid, then add glycolic acid and stir to obtain precursor solution A; S2. Precursor solution A undergoes a hydrothermal reaction to obtain precursor crystal nuclei with a certain [001] orientation and unnucleated amorphous material. The hydrothermal reaction temperature is 180℃ and the time is 30 minutes. After the S3 and S2 reactions are completed, the secondary hydrothermal reaction causes the precursor crystal nuclei obtained from S2 to continue to attach along the [001] direction and absorb amorphous material to form rice-grain-shaped precursors. The secondary hydrothermal reaction temperature is 140-150℃ and the time is 6-12 hours. S4. Calcine the rice-grain-shaped precursor obtained in S3 in air.

2. The method for preparing rice-grain-shaped TiO2-B with adjustable aspect ratio according to claim 1, characterized in that, In step S1, the concentration of dilute sulfuric acid is 0.1-0.15 mol / L, the mass ratio of titanium source to dilute sulfuric acid is in the range of 0.015-0.05, and the concentration of glycolic acid after dissolution is in the range of 1-1.5 mol / L.

3. The method for preparing rice-grain-shaped TiO2-B with adjustable aspect ratio according to claim 1 or 2, characterized in that, In step S1, the titanium source includes any one or more of tetrabutyl titanate, tetraethyl titanate, isopropyl titanate, tetraisobutyl titanate, and diisopropyl di(triethanolamine) titanate.

4. The method for preparing rice-grain-shaped TiO2-B with adjustable aspect ratio according to any one of claims 1, characterized in that, The glycolic acid mentioned in step S1 is added only after the titanium source has been completely hydrolyzed and the solution has changed from turbid to clear and transparent with no odor or volatilization.

5. The method for preparing rice-grain-shaped TiO2-B with adjustable aspect ratio according to any one of claims 1, characterized in that, In step S1, all raw materials except for the titanium source can be reused without reducing the purity of TiO2-B.

6. The method for preparing rice-grain-shaped TiO2-B with adjustable aspect ratio according to claim 1, characterized in that, In step S4, the calcination temperature range is 370-500℃, and the heating rate is 2-5℃ / min.

7. Rice-grain TiO2-B prepared by a method for preparing rice-grain TiO2-B with adjustable aspect ratio according to any one of claims 1-6.

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