A Titanium Carbide Thin Film Material, Preparation Method and Zinc-Ion Hybrid Capacitor

Abstract

The present invention relates to a titanium carbide thin film material, a preparation method thereof, and a zinc ion hybrid capacitor. The preparation method of the titanium carbide thin film material comprises the following steps: mixing titanium carbide nanosheets and an aqueous solution of an ammonium salt, performing ultrasonic treatment, then performing solid-liquid separation, and taking the upper liquid to obtain intercalated titanium carbide nanocolloid; adding a water-soluble salt to the intercalated titanium carbide nanocolloid, performing a reaction, then performing solid-liquid separation, washing with water, and drying to obtain a titanium carbide aerogel; performing molding by pressing on the titanium carbide aerogel to obtain a titanium carbide thin film material. The super-creased titanium carbide thin film prepared by the nanosheet twisting strategy of the present invention has significantly improved compression resistance. Under a pressure of 1 MPa, the microstructure of the electrode material does not change. In addition, the titanium carbide thin film material of the present invention has a lower tortuosity. Directly using it to construct an electrode can accelerate ion transport, significantly improve the kinetic performance of the electrode, and meet the requirements of high-quality load applications.

Description

Technical Field

[0001] The present invention relates to a titanium carbide thin film material, a preparation method thereof, and a zinc ion hybrid capacitor, belonging to the field of energy storage. Background Art

[0002] In modern energy storage technologies, the development of high-loading electrodes is a key factor in improving the energy density of energy storage devices such as capacitors and reducing the overall cost. High-loading electrodes enhance the overall energy density of energy storage devices by significantly increasing the content of active materials and reducing the inactive components inside the energy storage devices. However, when preparing thick electrodes to achieve high loading, a series of key challenges are faced. First, thick electrodes are prone to fracture during the drying process, which not only affects the structural integrity of the electrodes but may also lead to contact failure with the current collector. As the thickness increases, the stress and strain generated by the electrode material during the drying process increase significantly, thereby causing cracks and interlayer separation. In addition, the conductive agents and binders in the electrodes are often unevenly distributed during the coating process and tend to accumulate on the electrode surface. This non-uniformity reduces the conductivity of the electrodes and seriously affects their long-term cycling stability.

[0003] In recent years, self-supporting electrodes have been proposed as an emerging alternative. Self-supporting electrodes do not require binders, conductive agents, and current collectors, simplifying the manufacturing process while improving the structural integrity and energy density of the electrodes. Metal and carbon-based materials are often used as framework materials to support the formation of self-supporting electrodes with active materials, thereby enhancing electron and ion transport. However, in practical applications, ensuring the uniformity and consistency of the framework material and the active material composite remains a major challenge, especially when scaled up to an industrial scale. Therefore, directly using materials that can act as both a framework and have activity is an excellent choice.

[0004] MXenes, as a new type of two-dimensional material, have attracted much attention due to their excellent electrical conductivity and good ionic conductivity. However, current research mainly focuses on performance improvement at low loadings (1 - 2 mg cm -2 ), and the actual requirements at high loadings (exceeding 10 mg cm -2 ), such as Ti 3 C 2 T x MXene (titanium carbide) for example, although its conductivity is as high as 20000 S cm -1, however, under high load conditions, the close arrangement of the nanosheets prolongs the ion transport path, increases the ion transport resistance, results in a high tortuosity of the electrodes constructed therefrom, and thus limits their electrochemical performance. Among them, the tortuosity of the electrode is usually defined as the ratio between the actual transport distance of the ions in the electrode and the straight-line distance. Therefore, developing MXene films with low tortuosity is crucial for improving the performance under high load. Existing studies based on, such as 3D porous structures and vertically aligned MXene nanosheets, although reducing the tortuosity of the MXene films to a certain extent, are often limited in practical applications and ineffective in applications at the energy storage device level. Because during the encapsulation process of the energy storage device, the internal pressure is inevitable, which may cause the carefully designed MXene structure to collapse into a closely stacked structure, severely limiting its performance at the energy storage device level. Therefore, there is an urgent need to develop a new electrode material that can maintain the electrode structure and performance under high pressure and high load conditions. Summary of the Invention

[0005] In view of the deficiencies of the prior art, one of the objectives of the present invention is to provide a preparation method for a titanium carbide thin film material with a novel structure; the second objective of the present invention is to provide a titanium carbide thin film material; the third objective of the present invention is to provide a zinc ion hybrid capacitor.

[0006] To solve the above technical problems, the technical solution of the present invention is as follows:

[0007] A preparation method for a titanium carbide thin film material, comprising the following steps:

[0008] S1. Provide titanium carbide nanosheets;

[0009] S2. After mixing the titanium carbide nanosheets and an aqueous solution of ammonium salt, perform ultrasonic treatment, then perform solid-liquid separation, and take the upper liquid to obtain an intercalated titanium carbide nano-colloid;

[0010] Among them, the ammonium salt is one or more of tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrapropylammonium hydroxide;

[0011] S3. Add a water-soluble salt to the intercalated titanium carbide nano-colloid, after the reaction, perform solid-liquid separation, wash with water, and dry to obtain a titanium carbide aerogel;

[0012] Among them, the water-soluble salt is one or more of zinc salt, sodium salt, lithium salt, potassium salt, magnesium salt, iron salt, and calcium salt;

[0013] S4. Perform compression molding on the titanium carbide aerogel to obtain a titanium carbide thin film material.

[0014] Thus, through the nanosheet twisting strategy, the titanium carbide nanosheets form a super-folded structure. Specifically, during the intercalation process of the titanium carbide nanosheets, ammonium ions with a relatively large ionic radius are introduced first, and then through ion exchange, the ammonium ions are replaced with metal ions with a smaller ionic radius. Through ion exchange, the interlayer spacing of the titanium carbide nanosheets changes drastically, thereby realizing the twisting of the nanosheets and forming a super-folded structure. This structure can still maintain its structural integrity and maintain the interlayer voids under high-pressure conditions, and has good mechanical stability. When the obtained titanium carbide thin film material is applied to construct the electrode material of energy storage devices such as zinc-ion hybrid capacitors, it is found that the tortuosity of the electrode is significantly reduced, thereby significantly improving the ion transport efficiency and enabling the energy storage device to exhibit more excellent electrochemical performance.

[0015] Optionally, the preparation method of the titanium carbide nanosheets includes the following steps: Add Ti 3 AlC 2 to a hydrofluoric acid solution, keep the solution temperature at 25 - 40 °C, after reacting for 4 - 8 hours, centrifuge and wash with deionized water until the pH value of the supernatant is 5 - 6 to obtain titanium carbide nanosheets; wherein, the concentration of the hydrofluoric acid solution is 20 - 40 wt%, further 25 - 35 wt%.

[0016] Optionally, in S2, the concentration of the ammonium salt in the aqueous solution is 5 - 25 wt%, further 10 - 20 wt%, and still further 12 - 18 wt%.

[0017] Optionally, in S2, the ultrasonic treatment time is 30 - 90 min, further 45 - 75 min, and still further 50 - 70 min; during solid-liquid separation, centrifuge at a rate of 3000 - 4000 r / min for 30 - 90 min, and further, centrifuge at a rate of 3200 - 3800 r / min for 45 - 75 min.

[0018] Optionally, in S3, add an aqueous solution of a water-soluble salt dropwise to the intercalated titanium carbide nanocolloid, stir for 5 - 45 min (further 10 - 30 min), then centrifuge and wash with deionized water, and dry to obtain titanium carbide aerogel;

[0019] wherein, the concentration of the water-soluble salt in the aqueous solution of the water-soluble salt is 1.5 - 2.5 mol / L, preferably 1.8 - 2.3 mol / L, and the addition amount of the aqueous solution of the water-soluble salt is 0.2 - 0.3 times the volume of the titanium carbide nanocolloid, preferably 0.22 - 0.28 times.

[0020] Excess water-soluble salt can be preferably removed by water washing, which helps to obtain a purer titanium carbide aerogel.

[0021] Optionally, in S3, the drying method is freeze-drying. Optionally, the freeze-drying time is 40 - 60 h, and more preferably 45 - 55 h.

[0022] Optionally, the zinc salt is one or more of zinc sulfate, zinc chloride, and zinc nitrate.

[0023] Optionally, the sodium salt is one or more of sodium sulfate, sodium chloride, sodium nitrate, and sodium fluoride.

[0024] Optionally, the lithium salt is one or more of lithium sulfate, lithium nitrate, and lithium chloride.

[0025] Optionally, the potassium salt is one or more of potassium sulfate, potassium nitrate, potassium chloride, and potassium fluoride.

[0026] Optionally, the magnesium salt is one or more of magnesium sulfate, magnesium nitrate, and magnesium chloride.

[0027] Optionally, the iron salt is one or more of iron sulfate, iron chloride, and iron nitrate.

[0028] Optionally, the calcium salt is one or more of calcium chloride and calcium nitrate.

[0029] Optionally, in S4, the molding method is cold pressing, and the molding pressure is 0.8 - 1.2 MPa, more preferably 0.9 - 1.1 MPa.

[0030] Optionally, the thickness of the titanium carbide thin film material is 2 - 800 μm, more preferably 10 - 600 μm, even more preferably 20 - 50 μm, and still more preferably 30 - 40 μm.

[0031] Based on the same inventive concept, the present invention also provides a titanium carbide thin film material prepared by the above-mentioned preparation method.

[0032] Based on the same inventive concept, the present invention also provides a zinc ion hybrid capacitor including the titanium carbide thin film material prepared by the above-mentioned preparation method.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] (1) The super-creased titanium carbide thin film prepared by the nano-sheet twisting strategy of the present invention has a lower tortuosity, can provide a more direct ion transport channel, can effectively improve the ion transport efficiency. When it is used to construct an electrode, it can significantly improve the ion conductivity and electrochemical performance of the electrode, meeting the requirements of high-quality load applications. The prepared electrode exhibits excellent electrochemical performance under high-quality load conditions, including ultra-high areal capacitance and more than 93% cycling stability (after 10000 cycles at a mass load of 46.2 mg cm⁻²).

[0035] (2) The titanium carbide thin film material prepared by the present invention has a super-creased structure and strong mechanical stability. The constructed electrode can effectively maintain the structural integrity under high voltage conditions, avoiding breakage and peeling during the encapsulation and cycling of energy storage devices, thereby improving the long-term cycling stability of the electrode and ensuring the consistent performance of energy storage devices during multiple charge and discharge processes.

[0036] (3) The present invention not only provides a new material option for the development of high-energy density energy storage devices, but also broadens the potential prospects of titanium carbide materials in a variety of high-quality load applications.

[0037] (4) The titanium carbide thin film material prepared by the present invention provides more possibilities for various high-quality load energy storage applications, including portable devices, medical implants, and high-performance chip designs, etc.

[0038] (5) The preparation process flow of the present invention is short and easy to implement, facilitating industrial promotion and application.

[0039] (6) The titanium carbide thin film material of the present invention can be used as a self-supporting electrode material, directly used as a positive electrode without binders, conductive agents, and current collectors, which helps to further reduce the use of components without capacity contribution and also helps to simplify the electrode preparation process, making the electrode more environmentally friendly. Description of the Drawings

[0040] Figure 1 is the SEM image of the titanium carbide aerogel material obtained by freeze-drying. Among them, Figure 1 A is the SEM image of the titanium carbide aerogel material prepared in Example 1, Figure 1 B is the SEM image of pure titanium carbide aerogel powder.

[0041] Figure 2 is the SEM image of the titanium carbide thin film and pure titanium carbide thin film prepared in Example 1. Among them, Figure 2 A is the top view of the titanium carbide thin film prepared in Example 1, Figure 2 B is the cross-sectional view of the titanium carbide thin film prepared in Example 1, Figure 2 C is the top view of pure titanium carbide thin film, Figure 2 D is the cross-sectional view of pure titanium carbide thin film.

[0042] Figure 3 is the graph of the rate performance of the zinc-ion hybrid capacitor applied with the titanium carbide thin film prepared in Example 1.

[0043] Figure 4 is the graph of the electrochemical performance of the zinc-ion hybrid capacitor applied with the titanium carbide thin film prepared in Example 1 under high load.

[0044] Figure 5It is the graph of the cycling performance of the titanium carbide thin film prepared in Example 1 when applied to a zinc-ion hybrid capacitor.

[0045] Figure 6 It is the graph of the cycling performance of the high-loading titanium carbide thin film prepared in Example 1 when applied to a zinc-ion hybrid capacitor.

[0046] Figure 7 It is the digital photo of the titanium carbide thin film prepared in Example 1 before and after being weighted by a weight.

[0047] Figure 8 It is the electrochemical impedance spectrum of the zinc-ion hybrid capacitor assembled with the super-folded titanium carbide thin film prepared in Example 1.

[0048] Figure 9 It is the electrochemical impedance spectrum of the zinc-ion hybrid capacitor assembled with the pure titanium carbide thin film.

[0049] Figure 10 It is the top view of the titanium carbide thin film of Comparative Example 3.

[0050] Figure 11 It is the top view of the titanium carbide thin film of Comparative Example 4. Detailed Description of the Invention

[0051] The present invention will be described in detail below with reference to the embodiments. It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments may be combined with each other.

[0052] Example 1

[0053] Add 1 g of Ti 3 AlC 2 to 10 mL of hydrofluoric acid solution (30 wt%). Keep the solution temperature at 35 ºC. After reacting for 6 hours, centrifuge and wash with deionized water until the pH value of the supernatant is 5 - 6 to obtain titanium carbide nanosheets. Then, redisperse the titanium carbide nanosheets in 50 mL of an aqueous solution of 15 wt% tetramethylammonium hydroxide, perform water bath ultrasonic treatment for 1 hour (ultrasonic power is 300 W), and then centrifuge at 3500 revolutions per minute for 1 hour. Take the upper layer liquid to obtain an intercalated titanium carbide nanosheet colloid (yield is 70 wt%). Next, add 5 mL of zinc sulfate solution (2 mol / L) dropwise to 20 mL of the titanium carbide nanosheet colloid. After stirring at room temperature for 10 minutes, centrifuge with deionized water to remove the excess zinc sulfate. Then, perform freeze-drying on the centrifuged substrate to obtain a titanium carbide aerogel material (see Figure 1 A). Finally, under a pressure of 1 MPa, perform cold pressing on the obtained titanium carbide aerogel to form a film, and obtain a titanium carbide film material with a super-folded structure.

[0054] An assembled zinc-ion hybrid capacitor, in which the prepared thin film material is directly used as the positive electrode. The zinc-ion hybrid capacitor is assembled using a button cell configuration, with a zinc foil as the negative electrode. A glass microfiber membrane is used as the separator. The electrolyte is an aqueous solution of 2.5 M zinc trifluoromethanesulfonate (Zn(OTF) 2 ).

[0055] As Figure 1 can be seen, both the pure titanium carbide aerogel powder (omitting the above-mentioned zinc sulfate solution treatment step, specifically, directly freeze-drying the titanium carbide nanosheet colloid to obtain the titanium carbide aerogel material) and the super-creased aerogel powder exhibit a porous structure, which is formed by the sublimation of ice during the freeze-drying process. The difference is that the super-creased titanium carbide aerogel powder has a large number of crease structures.

[0056] As Figure 2 can be seen, compared with the pure titanium carbide thin film (formed by cold-pressing the above-mentioned pure titanium carbide aerogel material into a film under a pressure of 1 MPa), the prepared titanium carbide thin film material with a super-creased structure has an obvious creased porous structure. However, for the pure titanium carbide thin film obtained under the action of pressure, the structure becomes stacked and dense, and the pore structure completely disappears.

[0057] As Figure 3 can be seen, compared with the pure titanium carbide film, the electrochemical performance of the zinc-ion hybrid capacitor assembled with the titanium carbide thin film material prepared in Example 1 is significantly enhanced. Among them, the zinc-ion hybrid capacitor assembled with the super-creased titanium carbide film material can still achieve a specific capacitance retention rate of 51% at a current density of 50 A g -1 , while the zinc-ion hybrid capacitor assembled with the pure titanium carbide film can only achieve a specific capacitance retention rate of 4%.

[0058] As Figure 4 can be seen, the areal specific capacitance (surface capacitance) of the zinc-ion hybrid capacitor assembled with the super-creased titanium carbide film material changes linearly with the increase of the loading amount, and can reach up to 10.9 F cm -2 . Figure 5 As can be seen, the zinc-ion hybrid capacitor assembled with the titanium carbide thin film material prepared in Example 1 exhibits excellent cycling performance. At a current density of 20 Ag -1 , it can cycle more than 65000 times and maintain a specific capacitance of more than 99%, greatly exceeding the cycling performance of currently commercially available energy storage devices. As Figure 6 can be seen, the zinc-ion hybrid capacitor assembled with the titanium carbide thin film material prepared in Example 1 can still achieve excellent cycling performance even under high-quality loading conditions. After 10000 cycles at a loading of 46.2 mg cm⁻², it maintains a specific capacitance of more than 93%.

[0059] Among them, the galvanostatic charge-discharge test was carried out within a potential range of 0.1 - 1.1 V (vs. Zn²⁺ / Zn) and completed using a NEWARE battery tester (model CT-4008T).

[0060] See Figure 7 , the morphology of the obtained super-folded titanium carbide film showed no obvious change before and after being weighted by weights, indicating its strong mechanical stability.

[0061] The tortuosity test was carried out using a symmetric cell, which included two electrodes of the same type (i.e., super-folded titanium carbide film or pure titanium carbide film) and a separator (model: GF / D, manufacturer: Whatman) sandwiched between the two electrodes. In addition, impedance spectroscopy tests (model: CHI660, manufacturer: Chenhua) were also carried out on these symmetric cells to determine the ionic impedance (R ion ). The tortuosity (τ) can be calculated by the following equation:

[0062]

[0063] Among them, ε represents the porosity of the electrode, A is the area of the electrode, and k int is the intrinsic conductivity of the electrolyte (2.5 M zinc trifluoromethanesulfonate aqueous solution), and L represents the thickness of the electrode (the thickness of the super-folded titanium carbide film is 394.4 μm, and the thickness of the pure titanium carbide film is 215 μm).

[0064] As Figure 8 and Figure 9 shown, the tortuosity of the super-folded titanium carbide film was calculated to be 2.2, while that of the pure titanium carbide film was calculated to be 15.7. Among them, the area of the electrode was controlled to be 0.25 cm 2 , and the conductivity of the electrolyte was measured to be 5.08 S / m. It can be seen that the super-folded structure prepared in the present invention effectively reduces the tortuosity of the electrode and greatly improves its kinetic performance.

[0065] Comparative Example 1

[0066] Example 1 was repeated, except that: the concentration of the aqueous solution of tetramethylammonium hydroxide was 1 wt%.

[0067] As a result, the yield of the intercalated titanium carbide nanosheet colloid decreased significantly. The yield decreased from the original 70 wt% to 40 wt%.

[0068] Comparative Example 2

[0069] Example 1 was repeated, except that: the concentration of the aqueous solution of tetramethylammonium hydroxide was 50 wt%.

[0070] As a result, the yield of the intercalated titanium carbide nanosheet colloid decreased significantly. The yield decreased from the original 70 wt % to 50 wt %.

[0071] Comparative Example 3

[0072] Repeat Example 1, except that: an aqueous solution of 2M LiCl was used to replace the aqueous solution of tetramethylammonium hydroxide.

[0073] As a result, see Figure 10 , there was no obvious super-folded porous structure. The possible reason is that the ionic radii of lithium ions and zinc ions are similar, and the interlayer spacing of titanium carbide nanosheets will not change significantly during the ion exchange process, so the titanium carbide nanosheets will not be distorted. During the encapsulation process, under the action of pressure, the nanosheets form a tightly stacked thin film structure.

[0074] Comparative Example 4

[0075] Repeat Example 1, except that: the addition amount of zinc sulfate solution was 1 mL.

[0076] As a result, see Figure 11 , the pore structure of the thin film was not well-developed, and structural collapse occurred in some areas under the action of the encapsulation pressure. The possible reason is that the addition amount of zinc ions was insufficient to distort all the titanium carbide nanosheets.

[0077] The content clarified in the above embodiments should be understood that these embodiments are only used to illustrate the present invention more clearly, rather than to limit the scope of the present invention. After reading the present invention, various equivalent forms of modification by those skilled in the art fall within the scope defined by the appended claims of this application.

Claims

1. A method for preparing a titanium carbide thin film material, characterized in that: The steps include: S1, providing titanium carbide nanosheets; S2, mixing the titanium carbide nanosheets and the aqueous solution of ammonium salt, ultrasonically treating, and then separating the solid and liquid, and taking the upper layer of liquid to obtain intercalated titanium carbide nanocolloids; Wherein, the ammonium salt is tetramethylammonium hydroxide; the concentration of the ammonium salt in the aqueous solution is 12-20wt%; S3, adding an aqueous solution of a water-soluble salt to the intercalated titanium carbide nanocolloid, stirring for 5-45 minutes, washing with deionized water by centrifugation, and freeze-drying to obtain a titanium carbide aerogel; Wherein, the water-soluble salt is a zinc salt; the concentration of the water-soluble salt in the aqueous solution of the water-soluble salt is 1.5-2.5 mol / L, and the amount of the aqueous solution of the water-soluble salt added is 0.2-0.3 times the volume of the titanium carbide nanocolloid; S4, compression molding the titanium carbide aerogel to obtain a titanium carbide thin film material.

2. The preparation method according to claim 1, characterized in that: The preparation method of the titanium carbide nanosheets comprises the following steps: adding Ti3AlC2 into a hydrofluoric acid solution, maintaining the solution temperature at 25-40°C, reacting for 4-8 hours, centrifugally washing with deionized water until the pH value of the supernatant is 5-6, and obtaining titanium carbide nanosheets; wherein the concentration of the hydrofluoric acid solution is 20-40wt%.

3. The preparation method according to claim 1, characterized in that: In S2, the ultrasonic treatment time is 30-90 min; during solid-liquid separation, centrifugation is performed at a rate of 3000-4000 r / min for 30-90 min.

4. The preparation method according to any one of claims 1 to 3, characterized in that In S4, the compression molding method is cold compression molding, and the molding pressure is 0.8-1.2 MPa.

5. The preparation method according to any one of claims 1 to 3, characterized in that: The thickness of the titanium carbide film material is 2-800 μm.

6. A titanium carbide thin film material, characterized in that: The method is prepared by the preparation method according to any one of claims 1 to 5.

7. A zinc ion hybrid capacitor, characterized in that: The invention comprises a titanium carbide thin film material prepared by the preparation method according to any one of claims 1 to 5.

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