Ti-o electronic compound, lithium-sulfur battery electrode material, and preparation method and use thereof

Abstract

The application discloses a Ti-O electronic compound, a lithium-sulfur battery electrode material and a preparation method and application thereof, and belongs to the technical field of electrode material preparation. The preparation method is as follows: (1) uniformly mixing Ti powder and TiO2 powder according to the stoichiometric ratio of Ti and TiO2; (2) under the condition of 150-250 MPa, compressing the mixed powder obtained in the step (1) to obtain a sintered body; (3) wrapping the sintered body with Ti powder, and then performing high-temperature sintering, and cooling after the sintering is completed to obtain the Ti-O electronic compound. The application provides a simple preparation method for synthesizing the high-purity Ti-O electronic compound, and a lithium-sulfur battery positive electrode based on the Ti-O electronic compound as a catalytic carrier is prepared. By controlling key parameters such as powder particle size, compacted density, sintering atmosphere and temperature, the Ti-O electronic compound is realized to be embedded and sintered at high temperature to prepare a lithium-sulfur battery sulfur positive electrode with high rate performance.

Description

Technical Field

[0001] This invention belongs to the field of electrode material preparation technology, specifically relating to a Ti-O electronic compound, a lithium-sulfur battery electrode material, its preparation method, and its applications. Background Technology

[0002] Electron compounds are a special type of ionic compound in which some of the excess electrons are highly localized in the interstitial spaces of the crystal lattice, producing an anion-like effect. These locally located electron regions are called "pseudoatoms." Because these pseudoatoms in electron compounds readily break free from the lattice spaces that bind them and contribute to the outside, electron compounds generally possess extremely low work functions (2.6-4.0 eV) and extremely strong reducing properties, making them highly effective in catalytic reduction synthesis of ammonia and catalytic oxygen reduction reactions.

[0003] Currently, the main electron compounds studied include 7Al₂O₃·12CaO, Ca₂N, and LaScSi, but their synthesis and application have been limited. Firstly, many electron compounds exist only under extreme conditions such as extremely high pressure (≥2 GPa) and generally possess complex structures and rare elemental compositions, making their synthesis difficult. Secondly, the synthesis of many electron compounds requires extreme conditions and complex processes, such as extremely high temperatures and pressures, demanding sophisticated equipment. This limits the number of research institutions with the necessary resources, and the high cost and high barriers to entry restrict the breadth of research. Finally, most electron compounds are highly reactive, readily reacting with external media such as air, water, and organic reagents. The conditions required for experimental research on these electron compounds are demanding and difficult to control, further restricting their research and application. Considering these factors, the number of successfully discovered and synthesized electron compounds remains limited, with 7Al₂O₃·12CaO being the most widely studied. It is evident that theoretical research on electron compounds is still immature, and applied research is largely confined to a few catalysis fields.

[0004] Ti and O can form electronic compounds with the chemical formulas Ti2O, Ti3O, and Ti6O, which are stable at room temperature and pressure, have a safe and inexpensive elemental composition, and can exist stably in many media due to their self-passivating properties. Ti2O, in particular, has shown some promise in applied research. However, previous research has been limited to Ti2O electronic compounds, lacking expansion into Ti3O and Ti6O. Furthermore, previous synthesis methods for Ti2O have been complex and difficult to control in terms of purity. For example, the high-temperature molten salt electrolysis method at 800℃ synthesized relatively pure Ti2O, and the arc melting method at 2000℃ synthesized Ti2O and used it to load Pt metal catalysts. These methods require special equipment or extremely high temperatures. Other methods, such as laser pulse deposition and TiH2 sintering, also struggle to synthesize relatively pure Ti2O. Besides the aforementioned problems with Ti2O, research on the synthesis and experimental applications of Ti3O and Ti6O is lacking.

[0005] In the field of rechargeable batteries, lithium-sulfur batteries are currently considered one of the most promising alternatives to lithium-ion batteries due to their high theoretical energy density and the low cost of sulfur as a raw material. However, the slow reaction kinetics of lithium polysulfides and the shuttle effect of lithium polysulfides result in poor rate performance (difficult to reach above 1C) and poor cycle stability of lithium-sulfur batteries, limiting their further development and application. Therefore, designing catalytic cathode supports for lithium-sulfur batteries has become one of the hot research directions, but currently there are no catalytic supports associated with electron compounds. Summary of the Invention

[0006] To address the aforementioned shortcomings of existing technologies, this invention provides a Ti-O electron compound, a sulfur-based lithium battery electrode material, its preparation method, and its applications. This invention offers a simple method for synthesizing high-purity Ti-O electron compounds and developing lithium-sulfur battery cathodes using Ti-O electron compounds as catalyst supports. High-temperature sintering and embedding of Ti-O electron compounds into powder is achieved by controlling key parameters such as powder particle size, compaction density, sintering atmosphere, and temperature. Furthermore, a wet electrode process is used to prepare the sulfur cathode for lithium-sulfur batteries, achieving high-rate performance.

[0007] To achieve the above objectives, the technical solution adopted by the present invention to solve its technical problem is as follows:

[0008] The purpose of this invention is to provide a method for preparing Ti-O electronic compounds, comprising the following steps:

[0009] (1) Mix Ti powder and TiO2 powder evenly according to the stoichiometric ratio of Ti and TiO2;

[0010] (2) Press the mixed powder obtained in step (1) under the condition of 150-250 MPa to obtain a sintered body;

[0011] (3) Wrap the sintered body with Ti powder, then heat it to 1000-1300℃ at a rate of 2-5℃ / min for sintering. After sintering, cool it down to 400-500℃ at a rate of 2-5℃ / min, and then cool it naturally to obtain Ti-O electronic compound.

[0012] Furthermore, in step (1), the stoichiometric ratio of Ti to TiO2 is 3 to 11:1.

[0013] Furthermore, in step (1), the stoichiometric ratio of Ti to TiO2 is 3:1, 5:1, or 11:1.

[0014] Furthermore, in step (1), the particle size of Ti powder is 40-50 μm, and the particle size of TiO2 powder is 5-10 nm.

[0015] Furthermore, in step (1), the particle size of Ti powder is 50 μm, and the particle size of TiO2 powder is 5–10 nm.

[0016] Furthermore, in step (3), the particle size of the Ti powder is 40-50 μm, and its coating thickness is not less than 1 mm.

[0017] Furthermore, in step (3), the sintering temperature is 1250℃, the heating rate is 5℃ / min, and after cooling down to 500℃, it is naturally cooled at a cooling rate of 5℃ / min.

[0018] Another object of the present invention is to provide a Ti-O electronic compound prepared by the above method; the Ti-O electronic compound is a Ti2O, Ti3O or Ti6O electronic compound.

[0019] Another object of the present invention is to provide a method for preparing a lithium sulfur battery electrode material, characterized by comprising the following steps:

[0020] (1) The Ti-O electronic compound described in claim 7 is ground and pulverized, then mixed with sulfur powder in a mass ratio of 1:2 to 4, and then heated at 150 to 200°C for 10 to 15 hours to obtain Ti x O@S powder;

[0021] (2) Using Ti x O@S (x=2,3,6) powder is mixed with conductive carbon black and PVDF nmp solution and stirred evenly to obtain electrode slurry, which is then coated onto the surface of current collector and dried to obtain Ti-O electronic compound based lithium-sulfur battery electrode material.

[0022] Furthermore, in step (1), the dense protective layer on the surface of the Ti-O electronic compound is removed by grinding, and the particle size after pulverization is 500 nm.

[0023] Furthermore, in step (1), the mass ratio of Ti-O electronic compound powder to sulfur powder is 1:3.

[0024] Furthermore, the temperature in step (1) is 155°C and the heating time is 12 hours.

[0025] Further, step (1) Ti x In O@S powder, x can take the value of 2, 3 or 6.

[0026] Furthermore, the concentration of PVDF in the nmp solution is 4%.

[0027] Furthermore, Ti x The mass ratio of O@S (x=2,3,6) powder to conductive carbon black and PVDF is 7:2:1.

[0028] Furthermore, the amount of electrolyte used in step (2) should be precisely controlled, with a ratio of 25 μL / mg to sulfur.

[0029] Another object of the present invention is to provide a lithium sulfur battery electrode material, which is prepared by the above method.

[0030] Furthermore, the prepared lithium sulfur battery electrode material is a lithium sulfur battery cathode material.

[0031] Another object of the present invention is to provide the use of the above-mentioned sulfur lithium battery electrode material in the preparation of lithium batteries.

[0032] The beneficial effects of this invention are:

[0033] 1. This invention successfully developed a simple high-temperature sintering synthesis process. By mixing and compacting Ti powder and TiO2 and then sintering at high temperature, Ti2O, Ti3O, and Ti6O electronic compounds were successfully synthesized. The raw materials used in this process are simple (inexpensive Ti and TiO2 powders), the obtained samples have good purity and considerable yield, and the equipment used is simple (ordinary corundum tube furnace).

[0034] 2. This invention suppresses Ti oxidation during sintering through an embedding method, achieving precise control of the oxygen content in Ti-O electronic compounds. Furthermore, the compacted sheets facilitate solid-phase reactions and diffusion between the sintered powders. Using this method, a single sintering process producing tens of grams can be completed using only a tube furnace, sufficient for most experimental research. This yield can be further increased with the expansion of equipment. Compared to previous methods of Ti2O synthesis such as arc melting and molten salt electrolysis, this significantly improves yield and simplifies the process, greatly reducing the difficulty and research threshold for electronic compound synthesis.

[0035] 3. Compared to other electronic compounds, Ti-O electronic compounds have higher research value and broader research prospects. Due to their self-passivating properties, Ti-O series electronic compounds remain stable in a wide range of media, a characteristic that greatly expands the scope of application research for electronic compounds. Most electronic compounds are difficult to synthesize, have poor stability, and are difficult to research and apply, and they react with most common media and solvents such as air, water, and organic solvents. The Ti-O electronic compounds that are easily synthesized in this invention can remain stable in these media due to their self-passivating properties, which is also the reason why they can be extended to applications in lithium-sulfur batteries.

[0036] 4. Ti₂O and Ti₃O exhibited excellent performance as sulfur carriers in lithium-sulfur batteries, effectively overcoming the lithium polysulfide shuttle effect in sulfur cathodes and providing highly conductive chemisorption carriers for sulfur species. This enabled rapid electron transfer at the electrode, overcoming the weak electronic conductivity of electrochemically active materials such as elemental sulfur and Li₂S, and catalyzing and accelerating the decomposition of lithium polysulfides. The assembled lithium-sulfur battery achieved a capacity of 500 mAh / g at a high rate of 4C. Compared to previous research on electronic compounds, which was limited to oxygen reduction and ammonia reduction, this further expands the scope of application research for electronic compounds. Attached Figure Description

[0037] Figure 1 This is a schematic diagram illustrating the process of mixing Ti powder and TiO2 powder and pressing them into sintered sheets according to the present invention.

[0038] Figure 2 This is a schematic diagram of the present invention in which the above-mentioned sintering sheet is uniformly embedded in titanium powder and placed in a graphite boat;

[0039] Figure 3 This is a schematic diagram illustrating the high-temperature sintering preparation of Ti-O electronic compound sintered sheets according to the present invention;

[0040] Figure 4 This is a detection graph of the Ti-O electron-bearing compounds after pulverization according to the present invention;

[0041] Figure 5 The neutron diffraction pattern of Ti-O electronic compounds;

[0042] Figure 6 Ti for coating sulfur on the surface of powder x Detection plot of O@S(x=2,3,6);

[0043] Figure 7 This is a schematic diagram of electrode fabrication.

[0044] Figure 8 This is a schematic diagram of the assembly of a button cell battery device.

[0045] Figure 9 This is a graph showing the electrochemical performance of a button cell. Detailed Implementation

[0046] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0047] Example 1

[0048] A method for preparing a Ti-O electronic compound-based lithium-sulfur battery cathode, the specific process of which is as follows:

[0049] (1) Based on the stoichiometric ratio of Ti and O in the Ti-O electronic compound, Ti powder and TiO2 powder are mixed uniformly at a stoichiometric ratio of 3:1; wherein the particle size of Ti powder is 50 μm and the particle size of TiO2 powder is 10 nm.

[0050] (2) Press the mixed powder obtained in step (1) under a pressure of 200 MPa to form a circular sheet and obtain a sintered body;

[0051] (3) Place the sintered body in a graphite boat, completely wrap the sintered body with Ti powder with a coating thickness of 2 mm, and then heat it to 1250℃ at a rate of 5℃ / min for sintering. After sintering, cool it down to 500℃ at a rate of 5℃ / min and then cool it naturally to obtain Ti2O electronic compound.

[0052] (4) After removing the Ti2O electronic compound, polish the surface to remove the dense protective layer on the surface. Grind the polished sintered sheet into coarse powder in a mortar, and then ball mill it into fine powder with a particle size of 500nm.

[0053] (5) The Ti2O electronic compound powder was mixed with sulfur powder at a mass ratio of 1:3 and placed in a corundum boat. The mixture was heated at 155°C for 12 hours in an argon atmosphere in a tube furnace to melt the loaded sulfur and obtain Ti2O@S powder.

[0054] (6) The Ti2O@S powder is mixed with the N-methylpyrrolidone solution of conductive carbon black and PVDF in a ratio of 7:2:1 and stirred evenly to obtain an electrode slurry. Then, it is coated onto the surface of the aluminum foil current collector and dried in a vacuum oven to obtain an electrode sheet. The electrode sheet is then cut into different specifications as needed to obtain the Ti-O electronic compound-based lithium-sulfur battery cathode.

[0055] Example 2

[0056] A method for preparing a Ti-O electronic compound-based lithium-sulfur battery cathode, the specific process of which is as follows:

[0057] (1) Based on the stoichiometric ratio of Ti and O in the Ti-O electronic compound, Ti powder and TiO2 powder are mixed uniformly at a stoichiometric ratio of 5:1; wherein the particle size of Ti powder is 40 μm and the particle size of TiO2 powder is 5 nm.

[0058] (2) Press the mixed powder obtained in step (1) under a pressure of 150 MPa to form a circular sheet and obtain a sintered body;

[0059] (3) Place the sintered body in a graphite boat, completely wrap the sintered body with Ti powder with a coating thickness of 4 mm, and then heat it to 1250℃ at a rate of 5℃ / min for sintering. After sintering, cool it down to 500℃ at a rate of 5℃ / min and then cool it naturally to obtain Ti3O electronic compound.

[0060] (4) After removing the Ti3O electron compound, polish the surface to remove the dense protective layer on the surface. Grind the polished sintered sheet into coarse powder in a mortar, and then ball mill it into fine powder with a particle size of 500nm.

[0061] (5) Mix Ti3O electronic compound powder and sulfur powder in a mass ratio of 1:2 and place them in a corundum boat. Heat at 150°C for 15 hours in an argon atmosphere in a tube furnace to melt and load sulfur to obtain Ti3O@S powder.

[0062] (6) The Ti3O@S powder is mixed with the N-methylpyrrolidone solution of conductive carbon black and PVDF in a ratio of 7:2:1 and stirred evenly to obtain an electrode slurry. Then, it is coated onto the surface of the aluminum foil current collector and dried in a vacuum oven to obtain an electrode sheet. The electrode sheet is then cut into different specifications as needed to obtain the Ti-O electronic compound-based lithium-sulfur battery cathode.

[0063] Example 3

[0064] A method for preparing a Ti-O electronic compound-based lithium-sulfur battery cathode, the specific process of which is as follows:

[0065] (1) Based on the stoichiometric ratio of Ti and O in the Ti-O electronic compound, Ti powder and TiO2 powder are mixed uniformly in a stoichiometric ratio of 11:1; wherein the particle size of Ti powder is 45 μm and the particle size of TiO2 powder is 10 nm.

[0066] (2) Press the mixed powder obtained in step (1) under a pressure of 250 MPa to form a circular sheet and obtain a sintered body;

[0067] (3) Place the sintered body in a graphite boat, completely wrap the sintered body with Ti powder, with a coating thickness of 2.5 mm, and then heat it to 1250 °C at a rate of 5 °C / min for sintering. After sintering, cool it down to 500 °C at a rate of 5 °C / min and then cool it naturally to obtain Ti6O electronic compound.

[0068] (4) After removing the Ti6O electron compound, polish the surface to remove the dense protective layer on the surface. Grind the polished sintered sheet into coarse powder in a mortar, and then ball mill it into fine powder with a particle size of 500nm.

[0069] (5) Mix Ti6O electronic compound powder and sulfur powder in a mass ratio of 1:4 and place them in a corundum boat. Heat at 200°C for 10 hours in an argon atmosphere in a tube furnace to melt and load sulfur, thereby obtaining Ti6O@S powder.

[0070] (6) The Ti6O@S powder is mixed with the N-methylpyrrolidone solution of conductive carbon black and PVDF in a ratio of 7:2:1 and stirred evenly to obtain an electrode slurry. Then, it is coated onto the surface of the aluminum foil current collector and dried in a vacuum oven to obtain an electrode sheet. The electrode sheet is then cut into different specifications as needed to obtain the Ti-O electronic compound-based lithium-sulfur battery cathode.

[0071] Figures 1-3 This is a schematic diagram of the process for sintering and preparing Ti-O electronic compounds according to the present invention. Figure 1 This is a schematic diagram of how Ti powder and TiO2 powder are mixed in the proportion described in step (1) and then pressed into tablets in a tableting mold. Figure 2 This is a schematic diagram of the present invention in which the well-formed pressed sheet to be sintered is uniformly embedded in titanium powder and placed in a graphite boat. Figure 3 This is a schematic diagram showing the high-temperature sintering and the acquisition of Ti-O electronic compound sintered sheets.

[0072] like Figure 3As shown, the sintered sheet is obtained by heating to 1250℃ in an argon atmosphere in a tube furnace and then cooling. However, the surface of the sheet still has a dense protective film formed by Ti. This film is formed by the sintering and bonding of the embedded Ti at high temperature to the surface, effectively preventing the internal structure from being affected by the external atmosphere, thus achieving precise control of the oxygen content and the oxygen content in the Ti-O electron compound. It is worth noting that due to the limited distance of solid-phase diffusion and the limited sintering reaction rate, this Ti layer will not affect the internal purity. Polishing should continue until the surface loses its luster, exposing the uniform gray-black substance inside.

[0073] The Ti-O electron compound obtained by this invention was tested, and the results are shown in the figure. Figure 4 and Figure 5 This invention involves crushing and ball-milling Ti-O electronic compound sintered sheets to obtain powder with a particle size of 500 nm. Figure 4 The measured neutron diffraction spectrum is in good agreement with the theoretical calculations. Figure 5 The above test results demonstrate the reliability of the process of this invention and the purity of the synthesized Ti-O electronic compound. In particular, the complete diffraction peaks of the oxygen layer crystal plane indicate that the Ti-O electronic compound sintered body underwent an ordered-disorder phase transition during the cooling process, resulting in the ordered arrangement of the disordered oxygen atoms.

[0074] Figure 6 Ti for coating sulfur on the surface of powder x The detection map of O@S(x=2,3,6), Figure 7 This is a schematic diagram of electrode fabrication. Figure 8 This is a schematic diagram of the assembly of a button cell battery.

[0075] After cutting the electrode sheets into appropriately sized pieces, then... Figure 8 The assembly was carried out in the following order: negative electrode cap - lithium sheet - separator - electrolyte drop - positive electrode sheet - gasket - spring contact - positive electrode cap. Electrochemical tests were performed on the resulting coin cell to evaluate its catalytic performance; the results are shown below. Figure 9 .

[0076] like Figure 9As shown, the prepared Ti3O@S sulfur cathode maintains a high theoretical specific capacity of 500 mAh / g at a rate of 4C (1C = 1675 mAh / g), and no over-polarization occurs in its discharge curve. This is attributed to the accelerated decomposition reaction of lithium polysulfides. The Ti2O@S cathode achieves a relatively high specific capacity (800–1100 mAh / g) at low rates (0.1C), but its capacity decays rapidly. At higher rates (2C), its charge-discharge capacity is significantly lower than that of Ti3O@S. At 4C, the theoretical specific capacity of Ti2O@S drops sharply. Ti6O@S has a low specific capacity at low rates, and although it outperforms Ti2O@S at high rates (4C), it is still significantly lower than that of Ti3O@S. These results confirm the catalytic performance of Ti-O electron compounds in the decomposition reaction of lithium polysulfides and their promising application in lithium-sulfur batteries.

[0077] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing a Ti-O electron compound, characterized in that, Includes the following steps: (1) Mix Ti powder and TiO2 powder evenly according to the stoichiometric ratio of Ti and TiO2; (2) Press the mixed powder obtained in step (1) under a pressure of 150~250MPa to obtain a sintered body; (3) Wrap the sintered body with Ti powder, and then heat it to 1000-1300℃ at a rate of 2-5℃ / min for sintering. After sintering, cool it down to 400-500℃ at a rate of 2-5℃ / min, and then cool it naturally to obtain Ti-O electronic compound; the Ti-O electronic compound is Ti2O, Ti3O or Ti6O electronic compound.

2. The preparation method according to claim 1, characterized in that, In step (1), the stoichiometric ratio of Ti powder to TiO2 powder is 3:1, 5:1 or 11:

1.

3. The preparation method according to claim 1 or 2, characterized in that, In step (1), the particle size of Ti powder is 40~50μm and the particle size of TiO2 powder is 5~10 nm.

4. The preparation method according to claim 1, characterized in that, In step (3), the particle size of the Ti powder is 40~50μm and its coating thickness is not less than 1 mm.

5. The preparation method according to claim 1, characterized in that, In step (3), the sintering temperature is 1250℃, the heating rate is 5℃ / min, and after cooling down to 500℃, it is naturally cooled at a rate of 5℃ / min.

6. A Ti-O electronic compound, characterized in that, The Ti-O electronic compound is prepared by the method described in any one of claims 1 to 5; the Ti-O electronic compound is a Ti2O, Ti3O, or Ti6O electronic compound.

7. A method for preparing a sulfur-lithium battery electrode material, characterized in that, Includes the following steps: (1) The Ti-O electron compound described in claim 6 is ground and pulverized, then mixed with sulfur powder in a mass ratio of 1:2 to 4, and then heated at 150 to 200°C for 10 to 15 hours to obtain Ti x O@S powder; (2) Using Ti x The electrode slurry was prepared by using O@S powder, and then coated onto the surface of the current collector. After drying, the Ti-O electronic compound-based lithium-sulfur battery electrode material was obtained.

8. The preparation method according to claim 7, characterized in that, Step (1) Ti x In O@S powder, x can take the value of 2, 3 or 6.

9. The use of the sulfur lithium battery electrode material prepared by the method of claim 7 or 8 in the preparation of lithium batteries.

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