A kind of antimony trioxide and its preparation method and application

Abstract

The application relates to the field of inorganic materials, in particular to a kind of antimony trioxide and its preparation method and application, comprising: preparing PS-b-PVP copolymer template; PS-b-PVP copolymer template is immersed in treatment in antimony salt and ammonia water in turn; pyrolysis under inert gas protection, the antimony trioxide prepared in the application has unique nanotubular structure, effectively shortens the transmission path of lithium ion and electron, significantly inhibits the pulverization and structure collapse of electrode material in the charging and discharging process, thereby endowing it with high specific capacity and excellent cycle stability.

Description

Technical Field

[0001] This invention relates to the field of inorganic materials, specifically to antimony trioxide, its preparation method, and its applications. Background Technology

[0002] With the rapid development of portable electronic devices, electric vehicles, and large-scale energy storage systems, the demand for lithium-ion batteries with high energy density, long cycle life, and high safety is becoming increasingly urgent. As a key component of lithium-ion batteries, the anode material directly affects the overall performance of the battery. Currently, commercially available graphite anode materials, due to their relatively low theoretical specific capacity (approximately 372 mAh / g), are insufficient to meet the development requirements of next-generation high-energy-density lithium-ion batteries. Therefore, the development of novel high-capacity anode materials has become a current research hotspot.

[0003] Transition metal oxides such as tin oxide, cobalt oxide, and iron oxide have attracted widespread attention due to their high theoretical specific capacity. Among them, antimony trioxide (antimony trioxide) is an important anode material with advantages such as high theoretical specific capacity (approximately 1100 mAh / g), abundant resources, and relatively low cost. However, antimony trioxide suffers from severe volume expansion during charge and discharge, which leads to electrode material pulverization and structural collapse, resulting in rapid capacity decay and poor cycle stability, severely limiting its practical application.

[0004] To mitigate the volume effect of antimony trioxide (antimony trioxide), researchers have explored various strategies, such as nanostructuring antimony trioxide, combining it with carbon materials, and designing special hollow or porous structures. Among these, constructing antimony trioxide with a one-dimensional nanotube structure is considered an effective approach because the nanotube structure not only provides a shorter lithium-ion diffusion path but also reserves buffer space for volume expansion, thereby improving the cycling stability of the material. However, related research is still relatively limited. Summary of the Invention

[0005] Purpose of the invention: To address the above-mentioned technical problems, this invention proposes an antimony trioxide, its preparation method, and its application.

[0006] The technical solution adopted is as follows: In a first aspect, the present invention provides a method for preparing antimony trioxide, comprising the following steps: Templates for preparing polystyrene-b-poly(4-vinylpyridine) (PS-b-PVP) copolymers; The PS-b-PVP copolymer template was sequentially impregnated in an antimony salt solution and ammonia water. The impregnated product was pyrolyzed under inert gas protection to obtain antimony trioxide.

[0007] In a preferred embodiment of the present invention, the PS-b-PVP copolymer template has a nanotube structure. This nanotube structure, through subsequent impregnation and pyrolysis processes, can effectively guide the formation of antimony trioxide nanotubes with well-preserved morphology.

[0008] As a preferred embodiment of the present invention, the method for preparing the PS-b-PVP copolymer template specifically includes the following sub-steps: S1: Styrene, RAFT reagent, and free radical initiator are dissolved in dioxane, and after purging with nitrogen to remove oxygen, the reaction is carried out at 70-90℃. After the reaction is completed, the reaction solution is precipitated with methanol, the product is collected, washed, and dried under vacuum to obtain polystyrene macromolecular chain transfer agent. S2: Dissolve the polystyrene macromolecular chain transfer agent, free radical initiator and vinylpyridine obtained in step S1 in dioxane, remove oxygen by purging with nitrogen, and react at 60-80℃. After the reaction is completed, add the reaction solution to a water / tetrahydrofuran mixed solvent containing linear alkylbenzene sulfonic acid, continue stirring and collect the product, and wash, vacuum dry and grind in sequence to obtain the PS-b-PVP copolymer template.

[0009] The above preparation method employs reversible addition-fragmentation chain transfer (RAFT) living polymerization technology. First, a polystyrene macromolecular chain transfer agent with controllable molecular weight and narrow distribution is synthesized. Then, a polystyrene-b-poly(4-vinylpyridine) block copolymer is synthesized through a chain extension reaction. Subsequently, using linear alkylbenzene sulfonic acid as an inducer, the block copolymer is induced to self-assemble into a regular nanotube structure in a water / tetrahydrofuran mixed solvent. As a typical amphiphilic block copolymer, PS-b-PVP copolymers undergo microphase separation and self-assemble into specific aggregation morphologies (such as spherical, columnar, vesicular, and layered structures) in selective solvents (i.e., good solvents for one segment and poor solvents for another). Linear alkylbenzene sulfonic acid, through its specific interaction with the PVP segments, completely alters the self-assembly behavior of the block copolymer, inducing the formation of nanotubes rather than ordinary spherical micelles. This method has mild process conditions, good controllability of template structure, and does not require complicated post-processing removal (the template itself can be removed during subsequent pyrolysis, and carbon / nitrogen doping may be formed, further improving conductivity).

[0010] In a preferred embodiment of the present invention, the RAFT reagent is a dithioester compound. Dithioester compounds possess good chain transfer activity and functional group tolerance, enabling effective control of the polymer's molecular weight and molecular weight distribution. Specifically, it can be selected from any one of benzyl dithiobenzoate, phenethyl dithiobenzoate, or isopropylphenyl dithiobenzoate.

[0011] In a preferred embodiment of the present invention, the mass ratio of the polystyrene macromolecular chain transfer agent to vinylpyridine is 1:4-5. This ratio range is beneficial for forming block copolymers with suitable segment lengths, thereby obtaining stable nanotube structures during self-assembly. If the vinylpyridine ratio is too low, the PVP segments will be too short, which is not conducive to the formation of continuous tube walls; if the ratio is too high, it may lead to the formation of aggregates with other morphologies.

[0012] As a preferred embodiment of the present invention, the linear alkylbenzene sulfonic acid is dodecylbenzene sulfonic acid. Dodecylbenzene sulfonic acid, as an amphiphilic molecule, can selectively bind to PVP segments through hydrogen bonds or ionic interactions. Simultaneously, its hydrophobic alkyl chain has an affinity for the PS segment, thereby effectively inducing phase separation of the block copolymer in a water / tetrahydrofuran mixed solvent and assembling it into a nanotube structure.

[0013] In a preferred embodiment of the present invention, the mass ratio of water to tetrahydrofuran in the mixed solvent is 1:4-8. This solvent system provides suitable solubility and interfacial energy for the self-assembly of the block copolymer. An appropriate solvent ratio allows for precise control of the kinetics and thermodynamic equilibrium of the self-assembly process, which is beneficial for forming nanotubes with regular morphology and uniform size.

[0014] In a preferred embodiment of the present invention, the amount of linear alkylbenzene sulfonic acid used is 30%-50% of the mass of the polystyrene macromolecular chain transfer agent. This dosage range ensures sufficient interaction between surfactant molecules and block copolymers, effectively inducing the self-assembly process, while avoiding excessive surfactant residue from affecting subsequent template use.

[0015] As a preferred technical solution of the present invention, the temperature of pyrolysis If the temperature is too low, the template decomposes slowly, and antimony trioxide has not yet formed a continuous pipe wall. After the template is removed, the pipe wall is prone to collapse or breakage. If the temperature is too high, the template decomposes rapidly, and gas impact may cause perforation or collapse of the pipe wall. The preferred temperature is 500-550℃.

[0016] In a second aspect, the present invention provides antimony trioxide, which is prepared by the preparation method described in any of the technical solutions of the first aspect above.

[0017] Preferably, the antimony trioxide has a nanotube structure. This nanotube structure inherits the morphological characteristics of the PS-b-PVP copolymer template, exhibiting uniform tube diameter, high aspect ratio, and good structural integrity. This unique nanotube structure provides a rapid channel for lithium-ion transport during charge and discharge, while also providing an effective buffer space for volume expansion, thereby significantly improving the cycling stability of the material.

[0018] Thirdly, the present invention provides the application of the above-mentioned antimony trioxide in secondary batteries, particularly in lithium-ion battery anode materials.

[0019] When the antimony trioxide nanotubes prepared by this invention are used as anode materials for lithium-ion batteries, they exhibit high reversible specific capacity, excellent cycle stability, and good rate performance, effectively solving the problems of severe volume expansion and short cycle life of traditional antimony trioxide anode materials.

[0020] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects: This invention synthesizes block copolymers with controllable molecular weight using RAFT living polymerization technology, and combines it with self-assembly technology to precisely control the morphology of nanotube templates, thereby achieving controllable design of the final antimony trioxide structure.

[0021] Compared to the traditional hard template method, this invention uses a soft template formed by the self-assembly of block copolymers, which eliminates the need for complex template removal steps (such as etching with strong acid or strong alkali). The template can be removed and doped simultaneously during pyrolysis, simplifying the process and reducing production costs.

[0022] The antimony trioxide prepared by this invention has a unique nanotube structure, which effectively shortens the transport path of lithium ions and electrons and improves reaction kinetics. At the same time, the voids inside the nanotubes provide sufficient buffer space for volume expansion, which significantly inhibits the pulverization and structural collapse of the electrode material during charge and discharge, thereby endowing it with high specific capacity and excellent cycle stability.

[0023] The preparation method provided by this invention is not only applicable to antimony trioxide, but can also be extended to the preparation of one-dimensional nanostructures of other metal oxides or composite materials by adjusting the type of impregnated metal salt, and has good universality and prospects for widespread application. Attached Figure Description

[0024] Figure 1 This is a SEM image of the product prepared in Example 1.

[0025] Figure 2 This is a TEM image of the product prepared in Example 1. Detailed Implementation

[0026] Unless otherwise specified in the examples, the conditions were performed under standard conditions or as recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products. Techniques not mentioned in this invention refer to existing technologies. Unless otherwise specified, the following examples and comparative examples are parallel experiments, using the same processing steps and parameters. Example 1:

[0027] A method for preparing antimony trioxide: In a 250 mL three-necked flask, styrene monomer (20.8 g, 0.2 mol), RAFT reagent benzyl dithiobenzoate (0.52 g, 2.0 mmol), free radical initiator azobisisobutyronitrile (AIBN, 0.066 g, 0.4 mmol), and solvent dioxane (60 mL) were added. High-purity nitrogen was bubbled through the flask for 30 minutes to remove oxygen. The reaction flask was then placed in an oil bath at 80 °C and reacted under nitrogen protection for 12 hours. After the reaction was complete, the reaction solution was cooled to room temperature and slowly added dropwise to excess methanol (600 mL) to allow precipitation, resulting in a white precipitate. The precipitate was collected by filtration, washed three times with methanol, and dried to constant weight in a vacuum drying oven at 50 °C to obtain polystyrene macromolecular chain transfer agent (PS-RAFT).

[0028] The above-mentioned PS-RAFT (2.0 g), free radical initiator AIBN (0.016 g), and 4-vinylpyridine monomer (8.5 g) were dissolved in dioxane (50 mL) and added to a 100 mL three-necked flask. High-purity nitrogen was bubbled through the flask for 30 minutes to remove oxygen, followed by heating to 70 °C and reacting under nitrogen protection for 16 hours. After the reaction was complete, the reaction solution was slowly added dropwise to a water / tetrahydrofuran mixed solvent containing dodecylbenzenesulfonic acid (DBSA, 0.8 g) (water to tetrahydrofuran mass ratio 1:5, total mass 300 g), and stirring was continued at room temperature for 24 hours. After stirring, the product was collected by centrifugation and washed three times successively with deionized water and ethanol to remove unreacted raw materials and excess DBSA. The washed product was vacuum dried at 50 °C for 24 hours and then ground to obtain PS-b-PVP copolymer template powder. Scanning electron microscopy and transmission electron microscopy were performed on the PS-b-PVP copolymer template prepared in this embodiment. It can be clearly observed that it has a regular nanotube structure, indicating that the block copolymer has successfully self-assembled to form the target morphology.

[0029] 0.5 g of the above PS-b-PVP copolymer template was weighed and dispersed in 50 mL of a 0.1 mol / L antimony trichloride ethanol solution, and stirred and impregnated at room temperature for 12 hours. Subsequently, the product was collected by centrifugation and washed twice with ethanol to remove excess antimony salt adsorbed on the surface. The template impregnated with antimony salt was redispersed in 50 mL of a 5% (w / w) ammonia solution, and stirring was continued for 6 hours to allow antimony ions to hydrolyze in situ on the template surface to generate antimony hydroxide precursor. After centrifugation and washing, the resulting solid was placed in a tube furnace and heated to 500 °C at a heating rate of 2 °C / min under an argon atmosphere, and held at this temperature for 2 hours for pyrolysis. After natural cooling to room temperature, the product was obtained. SEM and TEM images are shown below. Figure 1 and Figure 2 .

[0030] The product prepared in this embodiment, conductive carbon black (Super P), and binder polyvinylidene fluoride were mixed at a mass ratio of 7:2:1, and an appropriate amount of N-methylpyrrolidone was added and ground evenly to form a slurry. The slurry was uniformly coated onto copper foil, dried under vacuum at 80°C for 12 hours, and then cut into circular electrodes with a diameter of 12 mm. Using a lithium metal sheet as the counter electrode, Celgard 2400 as the separator, and a 1 mol / L LiPF6 solution of ethylene carbonate / dimethyl carbonate (EC / DMC, volume ratio 1:1) as the electrolyte, a battery sample was assembled in an argon-filled glove box. Example 2:

[0031] This embodiment is basically the same as Example 1, except that the preparation conditions of the PS-b-PVP copolymer template are different. Specifically: The mass ratio of polystyrene macromolecular chain transfer agent (PS-RAFT) to 4-vinylpyridine was adjusted to 1:4. Dodecylbenzenesulfonic acid was used as the linear alkylbenzene sulfonic acid, accounting for 30% of the mass of PS-RAFT. The mass ratio of water to tetrahydrofuran in the mixed solvent was 1:4. Scanning electron microscopy and transmission electron microscopy observations of the PS-b-PVP copolymer template prepared in this example showed that it still exhibited a nanotubular structure with good uniformity in tube diameter.

[0032] The battery sample was assembled according to the method in Example 1. Example 3:

[0033] This embodiment is basically the same as Example 1, except that the preparation conditions of the PS-b-PVP copolymer template are different. Specifically: The mass ratio of polystyrene macromolecular chain transfer agent (PS-RAFT) to 4-vinylpyridine was adjusted to 1:5. Dodecylbenzenesulfonic acid was used as the linear alkylbenzene sulfonic acid, accounting for 50% of the mass of PS-RAFT. The mass ratio of water to tetrahydrofuran in the mixed solvent was 1:8. Scanning electron microscopy and transmission electron microscopy observations of the PS-b-PVP copolymer template prepared in this example showed that it still exhibited a nanotubular structure with good uniformity in tube diameter.

[0034] The battery sample was assembled according to the method in Example 1. Example 4:

[0035] This embodiment is basically the same as Example 1, except that the preparation conditions of the PS-b-PVP copolymer template are different. Specifically: The mass ratio of polystyrene macromolecular chain transfer agent (PS-RAFT) to 4-vinylpyridine was adjusted to 1:4. Dodecylbenzenesulfonic acid was used as the linear alkylbenzene sulfonic acid, accounting for 50% of the mass of PS-RAFT. The mass ratio of water to tetrahydrofuran in the mixed solvent was 1:4. Scanning electron microscopy and transmission electron microscopy observations of the PS-b-PVP copolymer template prepared in this example showed that it still exhibited a nanotubular structure with good uniformity in tube diameter.

[0036] The battery sample was assembled according to the method in Example 1. Example 5:

[0037] This embodiment is basically the same as Example 1, except that the preparation conditions of the PS-b-PVP copolymer template are different. Specifically: The mass ratio of polystyrene macromolecular chain transfer agent (PS-RAFT) to 4-vinylpyridine was adjusted to 1:5. Dodecylbenzenesulfonic acid was used as the linear alkylbenzene sulfonic acid, accounting for 30% of the mass of PS-RAFT. The mass ratio of water to tetrahydrofuran in the mixed solvent was 1:8. Scanning electron microscopy and transmission electron microscopy observations of the PS-b-PVP copolymer template prepared in this example showed that it still exhibited a nanotubular structure with good uniformity in tube diameter.

[0038] The battery sample was assembled according to the method in Example 1.

[0039] Comparative Example 1: It is basically the same as Example 1, except that PS nanotubes are used instead of PS-b-PVP copolymer template.

[0040] The preparation method of PS nanotubes is based on existing technology and is as follows: In 20 mL of deionized water, 10 mL of 0.02 M H₂SO₄ was added, followed by 0.5 mL of aniline, which was then ultrasonically dispersed until completely dissolved. 2.5 g of ammonium persulfate was weighed and dissolved in 20 mL of deionized water, and then 0.03 g of sodium dodecyl sulfate was added dropwise to the solution with stirring. The mixture was allowed to stand at room temperature for 6 h. The reaction product was then filtered, washed with distilled water and anhydrous ethanol, and finally dried under vacuum at 60 °C for 12 h. The product was then ground and ready for use. Scanning electron microscopy and transmission electron microscopy were used to observe the PS nanotubes prepared in this comparative example, confirming that they possessed a nanotubular structure.

[0041] The battery sample was assembled according to the method in Example 1.

[0042] Comparative Example 2: This comparative example provides antimony trioxide particles prepared using a traditional hydrothermal method as a comparison.

[0043] The preparation method of antimony trioxide particles is as follows: 2 mmol of antimony trichloride was dissolved in 40 mL of deionized water. While stirring, an appropriate amount of sodium hydroxide solution was added to adjust the pH to 9. The resulting suspension was transferred to a hydrothermal reactor and reacted at 180 °C under a sealed environment for 12 hours. After natural cooling, the product was collected by centrifugation, washed multiple times with deionized water and ethanol, dried at 80 °C, and then calcined at 500 °C under an argon atmosphere for 2 hours to obtain antimony trioxide particles. SEM observation showed that the product consisted of irregular particles with a size between 200 and 500 nm.

[0044] The battery sample was assembled according to the method in Example 1.

[0045] Comparative Example 3: The process was essentially the same as in Example 1, except that dodecylbenzenesulfonic acid was not included in the water / tetrahydrofuran mixed solvent. Scanning electron microscopy and transmission electron microscopy were performed on the PS-b-PVP copolymer template prepared in this comparative example. The results showed that the obtained product mainly consisted of irregular blocky aggregates and some short rod-like structures, failing to form a regular nanotube morphology. This indicates that without the addition of dodecylbenzenesulfonic acid, the block copolymer cannot effectively undergo selective self-assembly in the mixed solvent; the lack of directional induction between molecular chain segments leads to a disordered assembled structure. No further battery samples were prepared.

[0046] Comparative Example 4: It is basically the same as Example 1, except that the same volume of pure water is used instead of the water / tetrahydrofuran mixed solvent.

[0047] Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were performed on the PS-b-PVP copolymer template prepared in this comparative example. The results showed that a large amount of white precipitate was immediately produced upon the addition of pure water to the reaction solution. The collected product consisted of amorphous aggregated particles, and no ordered nanotube or micelle structures were observed. This is because pure water is a poor solvent for PS-b-PVP; the copolymer rapidly precipitates in pure water, preventing the completion of the dissolution-self-assembly process. No further battery samples were prepared.

[0048] Comparative Example 5: It is basically the same as Example 1, except that the same volume of pure tetrahydrofuran is used instead of the water / tetrahydrofuran mixed solvent.

[0049] Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were performed on the PS-b-PVP copolymer template prepared in this comparative example. The results showed that after adding pure tetrahydrofuran to the reaction solution, the system remained clear and homogeneous. The product obtained after drying was a dense, thin-film solid, and no nanotube structure was observed. This is because pure tetrahydrofuran is a co-solvent for PS-b-PVP and cannot form a selective solvent environment. The block copolymer is in a molecularly dissolved state in the solution and cannot undergo phase separation and self-assembly. After the solvent evaporates, only a homogeneous thin film is formed. No further battery samples were prepared.

[0050] Performance testing The battery samples from Examples 1-5 and Comparative Examples 1-2 were subjected to constant current charge-discharge tests at a voltage range of 0.01-3.0V and a current density of 1 A / g.

[0051] The test results are shown in Table 1: Table 1: As shown in Table 1 above, the antimony trioxide prepared by this invention has excellent electrochemical properties.

[0052] The PS-b-PVP nanotubes formed under the conditions of Example 1 exhibited regular structures, uniform diameters, and moderate wall thicknesses. After impregnation and pyrolysis, the resulting antimony trioxide completely inherited the template morphology and possessed excellent structural stability.

[0053] Comparative Example 1 uses a polyaniline template method to prepare PS nanotubes. The PS nanotubes lack pyridine groups that interact with antimony ions on their surface, resulting in poor adsorption capacity of antimony salts. During the impregnation process, the antimony ion loading is low and unevenly distributed. After pyrolysis, the antimony trioxide structure formed is discontinuous and has a large number of defects, leading to a decrease in electrochemical performance.

[0054] Comparative Example 2: Antimony trioxide prepared by hydrothermal method consists of irregular particles without buffer space. Due to the lack of volume buffering effect of nanotube structure, the volume expansion is severe during charging and discharging, resulting in particle pulverization, electrode structure collapse, and decreased electrochemical performance.

[0055] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing antimony trioxide, characterized in that, include: Preparation of PS-b-PVP copolymer template; The PS-b-PVP copolymer template was sequentially impregnated with antimony salt and ammonia water; Pyrolysis under inert gas protection.

2. The method for preparing antimony trioxide as described in claim 1, characterized in that, The PS-b-PVP copolymer template has a nanotube structure.

3. The method for preparing antimony trioxide as described in claim 2, characterized in that, The preparation method of the PS-b-PVP copolymer template is as follows: S1: Styrene, RAFT reagent, and free radical initiator are dissolved in dioxane, and after deoxygenation by purging with nitrogen, the reaction is carried out at 70-90℃. After the reaction is completed, the reaction solution is precipitated with methanol, and the product is collected, washed, and vacuum dried to obtain polystyrene macromolecular chain transfer agent. S2: Polystyrene macromolecular chain transfer agent, free radical initiator and vinylpyridine are dissolved in dioxane, and after deoxygenation by purging with nitrogen, the reaction is carried out at 60-80℃. After the reaction is completed, the reaction solution is added to a water / tetrahydrofuran mixed solvent containing linear alkylbenzene sulfonic acid, and the product is collected after stirring. The product is washed, vacuum dried and ground to obtain the PS-b-PVP copolymer template.

4. The method for preparing antimony trioxide as described in claim 3, characterized in that, The RAFT reagent is a dithioester compound.

5. The method for preparing antimony trioxide as described in claim 3, characterized in that, The mass ratio of polystyrene macromolecular chain transfer agent to vinylpyridine is 1:4-5.

6. The method for preparing antimony trioxide as described in claim 3, characterized in that, The linear alkylbenzene sulfonic acid is dodecylbenzene sulfonic acid.

7. The method for preparing antimony trioxide as described in claim 3, characterized in that, The mass ratio of water to tetrahydrofuran in the mixed solvent is 1:4-8.

8. The method for preparing antimony trioxide as described in claim 3, characterized in that, The amount of the linear alkylbenzene sulfonic acid used is 30%-50% of the mass of the polystyrene macromolecular chain transfer agent.

9. An antimony trioxide, characterized in that, It is prepared by the method of any one of claims 1-8.

10. The application of antimony trioxide prepared by the preparation method according to any one of claims 1-8 in secondary batteries.

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