Titanium oxide / titanium carbide accordion-like composite structure and preparation method and application thereof

Abstract

The application discloses a titanium oxide / titanium carbide accordion-shaped composite structure and a preparation method and application thereof, and belongs to the technical field of material chemistry. The preparation method takes commercial titanium aluminum carbon (Ti3AlC2) as a raw material, obtains titanium carbide (MXene) as a precursor by using a traditional hydrofluoric acid etching method, and takes high-temperature water vapor as a surface control agent (etching agent). By controlling conditions such as the temperature and reaction time of the water vapor, an in-situ grown titanium oxide / titanium carbide accordion-shaped heterostructure material is obtained. Compared with a traditional MXene surface control method, the method is relatively environmentally friendly and clean, the reaction is simple and controllable, the operation is safe and non-toxic, the requirement for equipment is not high, and the method is expected to realize industrialization. The accordion-shaped titanium oxide / titanium carbide composite structure can be obtained by the preparation method, and has a better application prospect in secondary battery energy storage.

Description

Technical Field

[0001] This invention belongs to the field of materials science and technology, specifically relating to an accordion-shaped composite structure of titanium oxide / titanium carbide, its preparation method, and its application. Background Technology

[0002] The scarcity, uneven distribution, and high cost of lithium resources have severely limited the development of lithium-ion batteries. However, potassium-ion batteries, as a novel type of alkali metal secondary battery, have attracted widespread attention due to the high abundance and low price of potassium resources in the Earth's crust, as well as the low redox potential of potassium. MXene materials, with their excellent conductivity, abundant surface functional groups, large interlayer spacing, and high specific surface area, have been widely used as anode materials in potassium-ion batteries. However, when used as anodes, MXene materials are prone to self-stacking, leading to structural disorder and resulting in low capacity and poor cycle stability in potassium-ion batteries. Therefore, modification of MXene is necessary. High-temperature steam etching can be used to modulate the surface of MXene, avoiding the drawbacks of traditional methods such as violent reactions, toxic side effects, and the introduction of impurities, while also improving the capacity of potassium-ion batteries. This provides a new approach to modifying MXene for its application in potassium-ion batteries.

[0003] MXene materials are widely used due to their excellent conductivity, large interlayer spacing, abundant surface functional groups, high specific area, good solution dispersibility, and low energy barrier. However, in secondary battery applications, the layer stacking caused by van der Waals forces between MXene layers inhibits the effective utilization of its surface active sites and rapid ion transport, thus affecting its specific capacity and rate performance. Therefore, when using MXene materials as battery electrode materials, surface modification is often required, such as widening the interlayer spacing, drilling, loading, doping, and exfoliation. However, traditional modification methods, such as acid, alkali, hydrothermal, additive, and melt methods, have drawbacks such as violent reactions, strong toxic side effects, difficulty in control, and introduction of unnecessary impurities. Titanium carbide, as an MXene material with a relatively mature preparation process, has been widely used in various functional devices.

[0004] When MXene materials are used as anodes in potassium-ion batteries, the self-stacking of their layered structure slows down the potassium-ion transport rate. Furthermore, the large radius of potassium ions leads to significant volume changes during insertion / extraction, resulting in lower battery capacity, poor cycle stability, and easy breakage of the electrode during long cycles. Traditional MXene modification methods suffer from violent reactions and difficulty in control. This invention utilizes a green and environmentally friendly high-temperature steam etching method to modulate the MXene surface, improving the functional group type ratio and constructing an oxide / MXene heterostructure. The oxide particles generated by steam etching provide more active sites, introducing higher pseudocapacitive contributions and increasing battery capacity. They also act as interlayer supports for MXene, maintaining the electrode material morphology and structure during battery charge and discharge, and enhancing battery cycle stability. Summary of the Invention

[0005] The primary objective of this invention is to provide a method for preparing an accordion-shaped titanium oxide / titanium carbide composite structure. This method is simple to operate, requires minimal equipment, and can efficiently and easily prepare accordion-shaped titanium oxide / titanium carbide composite materials. First, accordion-shaped titanium carbide is obtained using the traditional hydrofluoric acid etching MAX method as a precursor for the composite material. Then, environmentally friendly water vapor is used to rapidly oxidize and modify the MXene surface at high temperatures for a short period, ultimately yielding the in-situ grown titanium oxide / titanium carbide accordion-shaped composite material.

[0006] The second objective of this invention is to provide a titanium oxide / titanium carbide prepared by the above-described preparation method, which has a novel and stable structure. The titanium oxide particles grown in situ in the MXene interstitial space serve as interlayer pillars, which can buffer the structural damage caused by self-stacking during the material application process (such as buffering the large volume change of the electrode material caused by potassium ion insertion / extraction process), and can also provide more active sites. At the same time, the titanium oxide / titanium carbide heterostructure can bring beneficial synergistic effects, achieving long-cycle stability while improving battery capacity.

[0007] A third objective of this invention is to provide an application of the above-mentioned titanium oxide / titanium carbide accordion-shaped composite material in potassium-ion batteries.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A method for preparing a titanium oxide / titanium carbide accordion-shaped composite structure, comprising:

[0010] (1) Preparation of titanium carbide

[0011] Titanium aluminum carbon powder was etched by stirring in hydrofluoric acid solution at room temperature. After the reaction was completed, it was washed with deionized water until neutral, filtered to obtain a suspension, and the suspension was freeze-dried to obtain titanium carbide powder.

[0012] (2) Preparation of titanium oxide / titanium carbide composite structure

[0013] Titanium carbide powder is evenly spread into a quartz boat and placed against the bottom in the middle section of a tube furnace tube. The quartz boat carrying the titanium carbide powder is first heated in an argon atmosphere from room temperature to T1, then heated to T2 and held at T2 for 20 min to 40 min. At T2 temperature, a mixture of water vapor and argon gas is introduced into the tube, and the reaction is carried out for 5 to 20 min. The water vapor and argon gas are then stopped, the two ends of the furnace tube are sealed, and the reaction is continued for 5 min to 15 min. The water vapor channel is closed, and the final product powder is removed after annealing to room temperature in an argon atmosphere. Here, T1 = T2 - 100℃, and T2 is 300 to 600℃.

[0014] Furthermore, the concentration of the hydrofluoric acid is 40 wt%, and the etching time is 30 h to 40 h.

[0015] Furthermore, the ratio of titanium aluminum carbon (Ti3AlC2) to hydrofluoric acid is 500 mg : 15 mL. After etching, the soluble impurities generated in the process are washed away by multiple centrifugations and filtrations, and then vacuum freeze-drying is performed to obtain layered titanium carbide rich in fluorine functional groups.

[0016] Furthermore, the mixed gas is introduced by wetting argon gas in a gas washing bottle containing ultrapure water before entering the tube furnace. It is worth noting that the size and quantity of titanium dioxide particles can be controlled by adjusting the time and temperature of the steam / argon mixture. Moreover, steam replaces traditional additives, making it environmentally friendly and not introducing new impurities, thus achieving the surface modification effect of MXene. Both temperature and time must be appropriate; otherwise, excessive time or excessively high temperature will lead to severe oxidation of MXene, causing the accordion-like structure to collapse; excessively short time or excessively low temperature will not achieve the desired effect of significant titanium dioxide particle formation.

[0017] Furthermore, the temperature was increased from room temperature to T1 at a rate of 5℃ / min, and then increased to T2 at a rate of 3℃ / min.

[0018] Furthermore, under argon protection, the pressure inside the tubular furnace tube is 0.04 MPa ~ 0.06 MPa, and when a mixture of steam and argon is introduced, the pressure inside the tubular furnace tube is 0.01 MPa ~ 0.02 MPa.

[0019] A titanium oxide / titanium carbide accordion-shaped composite material is prepared by the above-mentioned method for preparing a titanium oxide / titanium carbide accordion-shaped composite structure.

[0020] Application of the above-mentioned titanium oxide / titanium carbide accordion-shaped composite material in potassium-ion batteries.

[0021] Furthermore, the titanium oxide / titanium carbide accordion-shaped composite structure, conductive carbon black, and CMC were mixed with deionized water at a mass ratio of 7:2:1, ground uniformly, coated onto copper foil, and dried. This mixture served as the negative electrode for a potassium-ion battery. The loading of the titanium oxide / titanium carbide accordion-shaped composite structure on the copper foil was 1 ± 0.2 mg / cm². -2 .

[0022] A potassium-ion half-cell was assembled using copper foil with a titanium oxide / titanium carbide accordion-shaped composite structure as the negative electrode, PP film and glass fiber as the separator, and KFSI DME solution as the electrolyte.

[0023] Specifically, the concentration of DME in the KFSI solution is 3 mol / L.

[0024] In the tube furnace reaction process, both the initial heating and the subsequent annealing are carried out under a high-purity argon atmosphere. Argon gas is introduced into a water-filled gas washing bottle to wet and carry water vapor into the furnace tube. The rate of gas introduction can be controlled by the bubbling rate of the water in the washing bottle. The mixture reacts with titanium carbide powder held in a quartz boat under specified temperature holding conditions. After annealing to room temperature, the titanium oxide / titanium carbide accordion-shaped composite material is obtained. Optionally, the heating rate of the tube furnace is 3~5℃ / min, the water vapor introduction time should be controlled to 3~10 min, and the holding temperature during the reaction stage should be controlled at 300~500℃. Within these ranges, the size and distribution of titanium oxide particles grown on the MXene layer can be effectively controlled, and appropriate temperatures and times can be selected as needed.

[0025] The beneficial effects of the embodiments of the present invention are:

[0026] This invention uses commercial titanium aluminum carbon (Ti3AlC2) as raw material and obtains titanium carbide (MXene) through a traditional hydrofluoric acid etching method. High-temperature steam is used as a surface modifier (etchant). By controlling the temperature and reaction time of the steam, an accordion-shaped heterostructure of titanium oxide / titanium carbide is obtained through in-situ growth. Compared with traditional MXene surface modifier methods, this method is more environmentally friendly and cleaner, the reaction is simple and controllable, the operation is safe and non-toxic, and the equipment requirements are not high, making it promising for industrialization. This preparation method yields an accordion-shaped titanium oxide / titanium carbide composite structure with novel and stable structure. The titanium oxide particles grown in situ in the MXene interstices act as interlayer pillars, buffering structural damage caused by self-stacking during material application (such as buffering the large volume changes of electrode materials caused by potassium ion insertion / extraction), and providing more active sites. Simultaneously, the titanium oxide / titanium carbide heterostructure brings beneficial synergistic effects, achieving long-cycle stability while improving battery capacity. It has excellent application prospects in secondary battery energy storage. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 The image shown is a low-magnification scanning electron microscope image of dried blocky titanium aluminum carbon MAX (Ti3AlC2) provided in Example 1 of the present invention.

[0029] Figure 2 This is a high-magnification scanning electron microscope image of dried blocky titanium aluminum carbon MAX (Ti3AlC2) provided in Example 1 of the present invention;

[0030] Figure 3 This is a low-magnification scanning electron microscope image of dried titanium carbide (MXene) provided in Example 1 of the present invention.

[0031] Figure 4 This is a high-magnification scanning electron microscope image of dried titanium carbide (MXene) provided in Example 1 of the present invention;

[0032] Figure 5 This is a low-magnification scanning electron microscope image of the dried titanium oxide / titanium carbide accordion-shaped composite material provided in Example 1 of the present invention.

[0033] Figure 6 This is a high-magnification scanning electron microscope image of the dried titanium oxide / titanium carbide accordion-shaped composite material provided in Example 1 of the present invention;

[0034] Figure 7 XRD patterns of titanium oxide / titanium carbide accordion-shaped composite materials prepared according to the present invention with varying time parameters of the argon and water vapor mixture (Example 1, Comparative Examples 1-3); fresh represents the sample of Comparative Example 1;

[0035] Figure 8 XRD patterns of titanium oxide / titanium carbide accordion-shaped composite materials prepared by the present invention with altered temperature parameters (Examples 1-4, Comparative Examples 1, 4 and 5);

[0036] Figure 9 The results of potassium storage performance tests of the titanium oxide / titanium carbide accordion-shaped composite material provided in Experimental Example 2 of the present invention at low to medium current densities in potassium-ion batteries;

[0037] Figure 10The results show the potassium storage performance of the titanium oxide / titanium carbide accordion-shaped composite material provided in Experimental Example 2 of this invention under high current density in a potassium-ion battery. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0039] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0040] Example 1

[0041] This embodiment provides a method for preparing a titanium oxide / titanium carbide accordion-shaped composite structure, the process of which is as follows:

[0042] S1. Mix 40% hydrofluoric acid and titanium aluminum carbon powder (scanning electron microscope, e.g.) Figure 1 and 2 (As shown) The hydrofluoric acid and titanium aluminum carbon powder were mixed in a 50 mL polytetrafluoroethylene beaker to obtain a mixed solution. The mixing ratio of hydrofluoric acid and titanium aluminum carbon powder was 15 mL: 500 mg.

[0043] S2. Place the mixture on a magnetic stirrer and stir at a constant speed at room temperature for 36 h;

[0044] S3. The mixed solution after the etching reaction is centrifuged and filtered multiple times with deionized water until the pH is neutral, and the soluble impurities generated in the process are washed away.

[0045] S4. Place the cleaned powder in a vacuum freeze dryer (-55℃~-60℃) for 12 hours to obtain accordion-shaped titanium carbide. Scanning electron microscopy image as shown below. Figure 3 and 4 As shown, it is shaped like an accordion.

[0046] S5. Take 300 mg of the accordion-shaped titanium carbide powder material obtained by the preparation method in Example 1, spread it evenly in a quartz boat (length:width:height = 200 mm:30 mm:15 mm), and place it on the bottom of the middle section of the tube furnace tube;

[0047] S6. A quartz boat carrying titanium carbide powder is first heated in an argon atmosphere in stages: the first stage is room temperature to 300℃, with a heating rate of 5℃ / min; the second stage is 300~400℃, with a heating rate of 3℃ / min, and a holding temperature of 400℃ for 30 min. During the heating stage, the pressure inside the tube furnace is 0.05MPa. At 400℃, argon gas is introduced into the tube furnace after being moistened in a 500 mL gas washing bottle containing 300 mL of ultrapure water (the bubbling rate in the gas washing bottle is controlled at about 60 bubbles / min). The pressure inside the tube furnace is about 0.02MPa, and the reaction is carried out for 5 min. The introduction of water vapor and argon gas is stopped, the two ends of the furnace tube are sealed, and the reaction continues for 5 min.

[0048] S7. Close the steam channel and continue annealing in an argon atmosphere (0.05 MPa inside the tube furnace) to room temperature. Then remove the final product powder and examine it under a scanning electron microscope as follows: Figure 5 and 6 As shown.

[0049] Example 2

[0050] This embodiment provides a method for preparing a titanium oxide / titanium carbide accordion-shaped composite material, the process of which is as follows:

[0051] S1. Take 300 mg of the accordion-shaped titanium carbide powder material obtained by the preparation method in Example 1, spread it evenly in a quartz boat (length:width:height = 200 mm:30 mm:15 mm), and place it on the bottom of the middle section of the tube furnace tube;

[0052] S2. A quartz boat carrying titanium carbide powder is first heated in an argon atmosphere in stages: the first stage is room temperature to 200℃, 5℃ / min; the second stage is 200~300℃, 3℃ / min, and held at 300℃ for 30 min. During the heating stage, the pressure inside the tube furnace is 0.05MPa. Argon gas is introduced into the tube furnace after being moistened with a gas washing bottle containing ultrapure water at 300℃. The pressure inside the tube furnace is about 0.02MPa. The reaction is carried out for 5 min. The introduction of water vapor and argon gas is stopped, the two ends of the furnace tube are sealed, and the reaction continues for 5 min.

[0053] S3. Close the steam channel and continue annealing in an argon atmosphere (the pressure inside the tube furnace is 0.05 MPa) until room temperature, then remove the final product powder.

[0054] Example 3

[0055] This embodiment provides a method for preparing a titanium oxide / titanium carbide accordion-shaped composite material, the process of which is as follows:

[0056] S1. Take 300 mg of the accordion-shaped titanium carbide powder material obtained by the preparation method in Example 1, spread it evenly in a quartz boat (length:width:height = 200 mm:30 mm:15 mm), and place it on the bottom of the middle section of the tube furnace tube;

[0057] S2. A quartz boat carrying titanium carbide powder is first heated in an argon atmosphere in stages: the first stage is room temperature to 400℃, 5℃ / min; the second stage is 400~500℃, 3℃ / min, and held at 500℃ for 30 min. During the heating stage, the pressure inside the tube of the tubular furnace is 0.05MPa. Argon gas is introduced into the tube furnace after being moistened by a gas washing bottle containing ultrapure water at 500℃. The pressure inside the tube of the tube is about 0.02MPa. The reaction is carried out for 5 min. The introduction of water vapor and argon gas is stopped, the two ends of the furnace tube are sealed, and the reaction continues for 5 min.

[0058] S3. Close the steam channel and continue annealing in an argon atmosphere (the pressure inside the tube furnace is 0.05 MPa) until room temperature, then remove the final product powder.

[0059] Example 4

[0060] This embodiment provides a method for preparing a titanium oxide / titanium carbide accordion-shaped composite material, the process of which is as follows:

[0061] S1. Take 300 mg of the accordion-shaped titanium carbide powder material obtained by the preparation method in Example 1, spread it evenly in a quartz boat (length:width:height = 200 mm:30 mm:15 mm), and place it on the bottom of the middle section of the tube furnace tube;

[0062] S2. A quartz boat carrying titanium carbide powder is first heated in an argon atmosphere in stages: the first stage is room temperature to 500℃, 5℃ / min; the second stage is 500~600℃, 3℃ / min, and held at 600℃ for 30 min. During the heating stage, the pressure inside the tube furnace is 0.05MPa. At 600℃, argon gas is introduced into the tube furnace after being moistened by a gas washing bottle containing ultrapure water. The pressure inside the tube furnace is about 0.02MPa. The reaction is carried out for 5 min. The introduction of water vapor and argon gas is stopped, the two ends of the furnace tube are sealed, and the reaction continues for 5 min.

[0063] S3. Close the steam channel and continue annealing in an argon atmosphere (the pressure inside the tube furnace is 0.05 MPa) until room temperature, then remove the final product powder.

[0064] Comparative Example 1

[0065] This comparative example provides a method for preparing a titanium oxide / titanium carbide accordion-shaped composite material, which is basically the same as that in Example 1, except that water vapor is not introduced and the heat preservation process lasts for 30 minutes.

[0066] Comparative Example 2

[0067] This comparative example provides a method for preparing a titanium oxide / titanium carbide accordion-shaped composite material, which is basically the same as that in Example 1, except that the time for passing a mixture of argon and water vapor is 10 min.

[0068] Comparative Example 3

[0069] This comparative example provides a method for preparing a titanium oxide / titanium carbide accordion-shaped composite material, which is basically the same as that in Example 1, except that the time for purging the mixture of argon and water vapor is 20 min.

[0070] Comparative Example 4

[0071] This comparative example provides a method for preparing a titanium oxide / titanium carbide accordion-shaped composite material, which is basically the same as Example 2, except that the tube furnace is heated in stages: the first stage is room temperature to 600℃, 5℃ / min; the second stage is 600~700℃, 3℃ / min, 700℃ is held for 30 min, and a mixture of argon and water vapor is introduced for the same duration.

[0072] Comparative Example 5

[0073] This comparative example provides a method for preparing a titanium oxide / titanium carbide accordion-shaped composite material, which is basically the same as Example 2, except that the tube furnace is heated in stages: the first stage is room temperature to 700℃, 5℃ / min; the second stage is 700~800℃, 3℃ / min, 800℃ is held for 30 min, and a mixture of argon and water vapor is introduced for the same duration.

[0074] Experimental Example 1

[0075] The layered titanium carbide and titanium oxide / titanium carbide composite materials of Examples 1-4 and Comparative Examples 1-5 were observed and recorded under an electron microscope. The results are shown in Table 1.

[0076] Table 1. Comparison of structural shapes of titanium oxide / titanium carbide composite materials

[0077]

[0078] As shown in Table 1, the preparation methods of Examples 1-4 of this invention successfully yielded titanium oxide / titanium carbide composite materials with an accordion-like layered structure. Compared to Example 1, Comparative Example 1 served as a blank control for its titanium carbide material under high-temperature conditions; Comparative Examples 2 and 3 involved extending the introduction time of the water vapor / argon mixture; and Comparative Examples 4 and 5 involved increasing the holding temperature during the introduction of the water vapor / argon mixture. Since water vapor acts as an oxidation modifier and reacts with titanium carbide in the tube, the higher the temperature, the more vigorous and obvious the oxidation reaction. Therefore, it is evident that with the extension of time and the increase of the holding temperature, the titanium oxide particles become more numerous and larger, the proportion of titanium oxide in the composite material also increases, and the MXene layered structure gradually deteriorates.

[0079] Figure 7 The XRD patterns of the titanium oxide / titanium carbide accordion-shaped composite materials provided in Examples 1 and Comparative Examples 1-3 are shown below. Figure 7 It can be seen that under the heat preservation condition of 400℃, as the time of mixed gas introduction increases, the anatase phase of titanium oxide in the composite material becomes more obvious in the XRD pattern, but still retains the characteristic peaks of titanium carbide at about 9°, 19°, 28° and 61°.

[0080] Figure 8 The XRD patterns of the titanium oxide / titanium carbide accordion-shaped composite materials provided in Examples 1-4, Comparative Examples 1, 4 and 5 are shown. When the mixed gas was introduced for a fixed time of 5 min, as the temperature continued to rise, the composite material gradually showed the anatase and rutile phases of titanium oxide while maintaining the original characteristic peaks of titanium carbide.

[0081] Depend on Figure 7 , Figure 8 It is known that both temperature and time should be appropriate; otherwise, excessive time or high temperature will lead to severe oxidation of MXene, causing the accordion-like structure to collapse. Insufficient time or low temperature will not achieve the desired effect of generating significant titanium dioxide particles. The optimal reaction temperature is 400℃ and the ventilation time is 5 minutes.

[0082] Experimental Example 2

[0083] The accordion-shaped composite material of titanium oxide / titanium carbide prepared in Example 1, and the accordion-shaped titanium carbide (MXene) material prepared in Comparative Example 1 after high-temperature heating in a high-purity argon atmosphere, were used as negative electrode materials in potassium-ion half-cells. The specific process is as follows:

[0084] Samples from Example 1 and Comparative Example 1 were mixed with conductive carbon black (SP) and sodium carboxymethyl cellulose (CMC) at a mass ratio of 7:2:1. The CMC was prepared using a 2% (w / w) aqueous solution with an appropriate amount of deionized water, and thoroughly ground in an agate mortar until the slurry was uniform and of suitable viscosity. The resulting slurry was coated onto a dry copper foil (current collector) wiped clean with anhydrous ethanol using a coater. After drying at 50°C for 12 hours in an oven, the foil was cut into multiple electrode sheets with a diameter of 14 mm using a special mold. The loading of the titanium oxide / titanium carbide accordion-shaped composite material or accordion-shaped titanium carbide on the electrode sheet was controlled at 0.8 mg / cm³. -2 Left and right. In a high-purity argon atmosphere glove box, assemble a potassium-ion half-cell in the following order: CR2032 negative electrode shell - material electrode sheet - PP separator - glass fiber separator - potassium-loaded pad - spring sheet - CR2032 positive electrode shell. A total of 3 mol L⁻¹ of material was added before and after placing the separator. -1 240 μL of KFSI electrolyte with DME as solvent was used. After battery assembly, the cells were allowed to stand for 12 h, and the half-cell performance was tested. The results are shown in Table 2 and [Table data missing]. Figure 9-10 As shown.

[0085] Table 2. Performance Comparison of Potassium-ion Half-cells

[0086]

[0087] As can be seen from Table 2, the potassium-ion half-cell prepared using the titanium oxide / titanium carbide accordion-shaped composite material provided in the embodiments of the present invention achieves a performance of 50 mA g⁻¹. -1 and 1 A g -1 At current densities of [specific values], their cycling capacities reach 245 mAh g. -1 and 169 mAh g -1 Furthermore, during high-current long-cycle operation, the capacity uniformly increases to 190 mAh g in the later stages. -1 The performance tends to stabilize; however, in comparative example 1, the accordion-shaped titanium carbide material without surface modification, exhibits a relatively low cycle capacity of only 150 mAh g⁻¹ when used as the negative electrode material at the same current density. -1 and 68 mAh g -1 Furthermore, the capacity decay is more pronounced under high current density (e.g.) Figure 9 and Figure 10 (As shown). This may be because the in-situ grown titanium oxide particles form natural pillars between the titanium carbide layers, inhibiting self-stacking during MXene cycling, buffering the volume changes caused by potassium ion insertion / extraction during charge and discharge, ensuring the structural integrity of the electrode material, and enhancing the cycle stability of the battery; at the same time, titanium oxide particles can provide more active sites, which is beneficial to improving the capacity of potassium-ion batteries.

[0088] In summary, this invention provides an accordion-shaped titanium oxide / titanium carbide (metal oxide / MXene) composite structure, its preparation method, and its applications. The preparation method uses commercial titanium aluminum carbon (Ti3AlC2) as raw material, employs a traditional hydrofluoric acid etching method to obtain titanium carbide (MXene) as a precursor, and uses high-temperature steam as a surface modifier (etchant). By controlling the temperature and reaction time of the steam, an in-situ grown accordion-shaped heterostructure of titanium oxide / titanium carbide is obtained. Compared with traditional MXene surface modifier methods, this method is more environmentally friendly and cleaner, the reaction is simple and controllable, the operation is safe and non-toxic, and the equipment requirements are not high, making it promising for industrialization. This preparation method can obtain an accordion-shaped titanium oxide / titanium carbide composite structure, which has excellent application prospects in secondary battery energy storage.

[0089] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. The application of a titanium oxide / titanium carbide accordion-shaped composite structure in potassium-ion batteries, characterized in that, The preparation process of the titanium oxide / titanium carbide accordion-shaped composite structure is as follows: (1) Preparation of titanium carbide Titanium aluminum carbon powder was etched by stirring in hydrofluoric acid solution at room temperature. After the reaction was completed, it was washed with deionized water until neutral, filtered to obtain a suspension, and the suspension was freeze-dried to obtain titanium carbide powder. (2) Preparation of titanium oxide / titanium carbide composite structure Titanium carbide powder is evenly spread into a quartz boat and placed against the bottom in the middle section of a tube furnace tube. The quartz boat carrying the titanium carbide powder is first heated in an argon atmosphere from room temperature to T1, then heated to T2 and held at T2 for 20 min to 40 min. At T2 temperature, a mixture of water vapor and argon gas is introduced into the tube and reacted for 5 min. The water vapor and argon gas are then stopped, the two ends of the furnace tube are sealed, and the reaction continues for 5 min to 15 min. The water vapor channel is then closed, and the final product powder is removed after annealing to room temperature in an argon atmosphere. T1 = T2 - 100℃, and T2 is 400℃.

2. The application according to claim 1, characterized in that, The concentration of the hydrofluoric acid is 40 wt%.

3. The application according to claim 1, characterized in that, The mixed gas is introduced by argon gas being wetted in a gas washing bottle containing ultrapure water before entering the tube furnace.

4. The application according to claim 1, characterized in that, The temperature was increased from room temperature to T1 at a rate of 5℃ / min, and then increased to T2 at a rate of 3℃ / min.

5. The application according to claim 1, characterized in that, When protected by argon, the pressure inside the tubular furnace tube is 0.04 MPa to 0.06 MPa. When a mixture of steam and argon is introduced, the pressure inside the tubular furnace tube is 0.01 MPa to 0.02 MPa.

6. The application according to claim 1, characterized in that, A titanium oxide / titanium carbide accordion-shaped composite structure, conductive carbon black, and CMC were mixed with deionized water in a mass ratio of 7:2:1, ground evenly, coated onto copper foil, and dried to serve as the negative electrode of a potassium-ion battery.

7. The application according to claim 6, characterized in that, The loading of the titanium oxide / titanium carbide accordion-shaped composite structure on copper foil was 1 ± 0.2 mg / cm². -2 .

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