Composite material and method for manufacturing the same

Abstract

The present application provides a composite material and a manufacturing method thereof, the method comprising: preparing a macon nano sheet from a macon, the macon having a chemical formula of M n+1 AX n wherein M is a transition metal element, A is a third main group element or a fourth main group element, X is a carbon element or a nitrogen element, and n is 1, 2 or 3; preparing titanium hydroxide on the macon nano sheet; and converting the titanium hydroxide on the macon nano sheet into titanium dioxide to prepare a composite material.

Description

Technical Field

[0001] This application relates to composite materials and methods for manufacturing the same, particularly composite materials including malicene and methods for manufacturing the same. Background Technology

[0002] Maicoene has rapidly become a research hotspot in the field of energy storage materials due to its high electrical conductivity, large specific surface area, tunable composition, and surface functional groups. However, existing maicoene nanosheets are prone to collapse and stacking, which severely reduces the accessibility of internal active sites and the stability of the overall structure. In addition, existing maicoene nanosheet manufacturing methods, which use liquid-phase etching under acidic conditions to synthesize maicoene nanosheets, contain a large number of titanium defects (metastable titanium atoms) and inert functional groups (such as -F, -O, -OH, etc.), which greatly limits the application of synthesized maicoene nanosheets in surface-related electrochemical reactions.

[0003] For composite materials containing titanium dioxide and maicoene, existing manufacturing methods primarily rely on hydrothermal synthesis or high-temperature oxidation, making it difficult to precisely control the size, morphology, and distribution of titanium dioxide. Furthermore, the manufactured titanium dioxide particles or nanosheets are often composited on the outer surface of maicoene and are relatively large, limiting the full utilization of titanium dioxide's energy storage performance. Moreover, as a semiconductor material, titanium dioxide exhibits poor conductivity, severely restricting its practical application in energy storage systems. In addition, the uncontrollable structure and composition mean that the structure-structure-surface / interface properties-electrochemical properties of the composite material remain unclear, making it difficult to guide its practical application in energy storage systems and hindering demand-driven development. Summary of the Invention

[0004] According to a first aspect, this application provides a method for manufacturing a composite material, the method comprising: forming macoene into macoene nanosheets, wherein the macoene has the chemical formula M n+1 AX n Where M is a transition metal element, A is a group III or group IV element, X is carbon or nitrogen, and n is 1, 2 or 3; titanium hydroxide is formed on the maicoene nanosheets; and the titanium hydroxide on the maicoene nanosheets is converted into titanium dioxide to form a composite material.

[0005] According to a second aspect, this application provides a composite material for an electrochemical energy storage system. The composite material includes malicene nanosheets having the chemical formula M... n+1 AX n M is a transition metal element, A is a group III or group IV element, X is carbon or nitrogen, and n is 1, 2 or 3; and titanium dioxide particles dispersed on the maicoene nanosheets. Attached Figure Description

[0006] Different embodiments of this application will be described below with reference to the following figures in a detailed description:

[0007] Figure 1 This is a schematic diagram of a method according to an embodiment of this application.

[0008] Figure 2 yes Figure 1 A schematic diagram illustrating exemplary specific steps of the method shown.

[0009] Figure 3 yes Figure 1 A schematic diagram of the additional steps of the method shown.

[0010] Figure 4 yes Figure 1 A schematic diagram illustrating exemplary specific steps of the method shown.

[0011] Figure 5 yes Figure 1 A schematic diagram illustrating exemplary specific steps of the method shown.

[0012] Figure 6 This is an example of a method for UD-TiO2 / f-Ti3C2T according to an embodiment of this application. x A schematic diagram of the synthesis pathway for heterostructures.

[0013] Figures 7A to 7I Microscopic images of different samples from examples of methods according to embodiments of this application are shown, wherein Figure 7A , Figure 7B and Figure 7C They are f-Ti3C2T x Scanning electron microscope images and transmission electron microscope images, Figure 7D and Figure 7E They are UD-TiO2 / f-Ti3C2T x Scanning electron microscope (SEM) images and transmission electron microscope (TEM) images of heterostructures. Figure 7G and Figure 7H They are UD-TiO2 / f-Ti3C2T x High-resolution transmission electron microscope images and elemental distribution maps of heterostructures. Figure 7I yes Figure 7F The illustration shows UD-TiO2 / f-Ti3C2T. x The corresponding particle size distribution of TiO2 nanoparticles supported on the heterostructure.

[0014] Figure 8 Illustration a shows X-ray diffraction patterns of different samples of a method example according to an embodiment of this application, including Ti3AlC2 and Ti3C2T. xf-Ti3C2T x and UD-TiO2 / f-Ti3C2T x The sub-illustration of illustration a is a magnified portion of the typical (002) peak. Illustration b shows Ti3C2T x f-Ti3C2T x and UD-TiO2 / f-Ti3C2T x The nitrogen adsorption-desorption isotherm is shown in Figure c, with the corresponding particle size distribution. Figures d, e, and f show the f-Ti3C2T... x and UD-TiO2 / f-Ti3C2T x The F1s spectrum, O1s spectrum and Ti2p spectrum.

[0015] Figure 9A This shows UD-TiO2 / f-Ti3C2T x The electrode is at 0.1 mV s -1 The cyclic current-voltage curve below, Figure 9B Showing f-Ti3C2T x and UD-TiO2 / f-Ti3C2T x Rate performance, Figure 9C This shows UD-TiO2 / f-Ti3C2T x Discharge / charge curves of the electrode at different current densities. Figure 9D This shows UD-TiO2 / f-Ti3C2T x The electrode is at 0.02Ag. -1 The discharge / charge curve below, Figure 9E A comparison of rate performance with existing technologies is shown. Figure 9F Showing f-Ti3C2T x Electrode and UD-TiO2 / f-Ti3C2T x The electrode is at 0.02Ag. -1 Under the following cycle performance, Figure 9G Showing f-Ti3C2T x Electrode and UD-TiO2 / f-Ti3C2T x Electrode in 2Ag -1 The loop performance is as follows.

[0016] Figure 10 Illustration a shows UD-TiO2 / f-Ti3C2T x Cyclic voltammetry curves of the electrode at different scan rates are shown in inset b, which illustrates UD-TiO2 / f-Ti3C2T. x Electrode and f-Ti3C2T xThe comparison of the b-values ​​of the electrodes is shown in Figure c, which illustrates the comparison of diffusion control and capacitance contribution ratios at different scan rates. Figure d shows the UD-TiO2 / f-Ti3C2T electrode. x Electrode and f-Ti3C2T x The constant current intermittent titration curve of the electrode during the first discharge / charge process, illustrated in inset e, shows UD-TiO2 / f-Ti3C2T. x Constant current intermittent titration curves of the electrode during the first discharge and charge process and the corresponding Na + Diffusion coefficient, Figure f shows f-Ti3C2T x Constant current intermittent titration curves of the electrode during the first discharge and charge process and the corresponding Na + Diffusion coefficient.

[0017] Figure 11 Illustration a shows a side view and a top view of a TiO2 surface, illustration b shows a side view and a top view of a Ti3C2 surface, illustration c shows a side view and a top view of an F-terminated Ti3C2 surface, illustration d shows a side view and a top view of an OH-terminated Ti3C2 surface, and illustration e shows the corresponding sodium adsorption energies on different surfaces.

[0018] Figure 12 Illustration a shows a side view and a top view of the new Ti3C2, illustration b shows a side view and a top view of Ti3C2F2, and illustration c shows a side view and a top view of Ti3C2(OH)2.

[0019] Figure 13 Illustrations a and b show scanning electron microscope images of Ti3AlC2, and illustrations c and d show Ti3C2T x Scanning electron microscope images.

[0020] Figure 14 Illustration a shows calcined f-Ti3C2T x f-Ti3C2T x UD-TiO2 / f-Ti3C2T x UD-TiO2 / f-Ti3C2T before calcination x The X-ray diffraction pattern of the sample, with sub-inset in inset a showing the magnified region of the typical (002) peak, and inset b showing f-Ti3C2T x UD-TiO2 / f-Ti3C2T x X-ray photoelectron spectrum of the sample.

[0021] Figure 15 Illustration a shows f-Ti3C2T x Cyclic voltammetry curves of the electrode, illustrated in inset b, show f-Ti3C2T xDischarge / charge curves of the electrode at different current densities, with inset c showing f-Ti3C2T x The electrode is at 0.02Ag. -1 The constant current discharge / charge curves of UD-TiO2 / f-Ti3C2T are shown in inset d. x Electrode and UD-TiO2 / f-Ti3C2T before calcination x Rate performance of the electrodes.

[0022] Figure 16 Illustration a shows f-Ti3C2T x Cyclic voltammetry curves of the electrode at different scan rates are shown in inset b, which illustrates UD-TiO2 / f-Ti3C2T. x Electrode and f-Ti3C2T x The Nyquist plot of the electrodes, sub-illustration of inset b shows the corresponding equivalent circuit, and inset c is Z' with ω -1 / 2 Relationship diagram in the lower frequency region.

[0023] Figure 17 The current step diagram used to determine the parameters is shown. Detailed Implementation

[0024] The following detailed description is based on the accompanying drawings, which illustrate details and embodiments of the present application for illustrative purposes. Features described in the context of one embodiment may be adapted accordingly to the same or similar features in other embodiments, even if not explicitly described in those other embodiments. The application and / or combination and / or substitution of features described in the context of one embodiment may be adapted accordingly to the same or similar features in other embodiments.

[0025] In the context of different embodiments, the articles “a,” “an,” and “the” used with respect to features or elements include references to one or more features or elements.

[0026] In the context of different embodiments, the term “about” or “approximately” applied to numerical values ​​covers exact values ​​and reasonable differences as commonly understood in the relevant art, such as within 10% of a specified value.

[0027] The term “and / or” as used herein includes any and all combinations of one or more of the listed items.

[0028] As used herein, “comprising” means, but is not limited to, anything that follows the word “comprising.” Therefore, the use of the term “comprising” indicates that the listed elements are necessary or mandatory, but other elements are optional and may or may not be present.

[0029] As used herein, “consisting of” refers to the content included within the phrase “consisting of”. Therefore, the use of the phrase “consisting of” indicates that the listed elements are necessary or mandatory, and that no other elements exist.

[0030] The specific implementation of each embodiment will be described below with reference to the accompanying drawings.

[0031] According to a first embodiment of this application, this application relates to a method 100 for manufacturing a composite material. For example... Figure 1 As shown, method 100 includes step 110, forming macoene into macoene nanosheets, wherein the macoene has the chemical formula M n+1 AX n Where M is a transition metal element, A is a Group 3 or Group 4 element, X is carbon or nitrogen, and n is 1, 2, or 3. Method 100 further includes step 120, forming titanium hydroxide on the maicoene nanosheets, and step 130, converting the titanium hydroxide on the maicoene nanosheets into titanium dioxide to form a composite material.

[0032] Preferably, in the first embodiment of this application, the maicoene is a material selected from the group consisting of Ti2AlC, Ti2SiC, Ti3SiC2, Ti3AlC2, and Ti4AlN3.

[0033] Preferably, in the first embodiment of this application, as Figure 2 As shown, step 110 includes steps 112 and 114. In step 112, the maccolin is applied to a hydrogen chloride solution containing lithium fluoride to generate an intermediate product. In step 114, the intermediate product is dispersed in deionized water in an ice bath and sonicated under a protective atmosphere to generate maccolin nanosheets. The solution containing the maccolin nanosheets is then centrifuged at 3500 rpm for 1 hour to collect the supernatant, which is then freeze-dried to obtain maccolin nanosheet powder.

[0034] Preferably, in the first embodiment of this application, the weight ratio of lithium fluoride to maicoene is in the range of 1:0.65 to 1:1.

[0035] Preferably, in the first embodiment of this application, as Figure 3 As shown, method 100 further includes step 140 between steps 110 and 120. In step 140, the maicoene nanosheets are immersed in anhydrous ethanol and suspended in an ice bath under a protective atmosphere.

[0036] Preferably, in the first embodiment of this application, as Figure 4As shown, step 120 includes step 122. In step 122, ammonia and a titanium source are applied to the suspension to generate titanium hydroxide on the maicoene nanosheets. For example, the ammonia can be a concentrated ammonia solution with a mass concentration of 28%, and the titanium source can be tetrabutyl titanate (TBOT). In this application, the titanium source serves as the source of titanium in titanium hydroxide and subsequent titanium dioxide, and the maicoene nanosheets are not used as the source of titanium in titanium hydroxide and subsequent titanium dioxide. In other words, according to this embodiment, under the action of the titanium source applied to the suspension, the maicoene nanosheets do not participate in the reaction to generate titanium hydroxide and the reaction to generate subsequent titanium dioxide, thereby avoiding structural damage caused by the consumption of maicoene nanosheets and maintaining the integrity of the maicoene nanosheet structure. In one example, when tetrabutyl titanate, as a titanium source, is applied to a suspension containing maicoene nanosheets, trace amounts of water can initiate the hydrolysis process of tetrabutyl titanate, as shown in reaction formula (1):

[0037] Ti(OC4H9)4+4H2O→Ti(OH)4+4C4H9OH (1)

[0038] The controlled application of ammonia slightly increases the pH value, slowing down the hydrolysis of the titanium source, thereby obtaining titanium hydroxide and subsequent titanium dioxide particles that grow uniformly on the maicoene nanosheets. Therefore, the controlled application of ammonia can avoid or at least reduce the problem of particle agglomeration caused by accelerated hydrolysis of the titanium source due to excessively rapid ammonia application.

[0039] In this application, "uniform" means that the size of the individual particles dispersed on the maicoene nanosheets is in the range of 10 nm to 35 nm, and that approximately 80 to 100 dispersed individual particles are carried on a maicoene nanosheet with an area of ​​1000 nm × 1000 nm. In this application, "slight increase in pH value" means that the pH value is in the range of 8 to 9.

[0040] Additionally, in step 122, metastable titanium atoms on the surface of the maicoene nanosheets are consumed, and the metastable titanium atoms themselves or the vacancies formed after they detach from the surface of the maicoene nanosheets serve as nucleation sites for titanium hydroxide and subsequent titanium dioxide.

[0041] Preferably, in the first embodiment of this application, as Figure 5 As shown, step 130 includes step 132. In step 132, the titanium hydroxide on the maicoene nanosheets is calcined to generate titanium dioxide. In one example, the titanium hydroxide generated by the reaction can be calcined after tetrabutyl titanate, as a titanium source, is applied to a suspension containing maicoene nanosheets, as shown in reaction formula (2):

[0042] Ti(OH)4→TiO2+2H2O (2)

[0043] Method 100 can obtain uniformly distributed titanium dioxide nanoparticles, control the size of the titanium dioxide nanoparticles, and, compared with conventional direct oxidation methods, prevent the aggregation and uneven growth of titanium dioxide nanoparticles. Additionally, Method 100 can increase the interlayer spacing of maccene nanosheets to prevent the recombination of maccene nanosheets and reduce over-oxidation of maccene. By consuming metastable titanium atoms, Method 100 can mitigate the degradation of maccene, thereby enhancing the stability of maccene.

[0044] Preferably, in the first embodiment of this application, the number of maicoene nanosheets is 5 to 10 layers. Accordingly, the maicoene nanosheets possess higher conductivity, higher specific surface area, and reduced complexity of ion diffusion paths, thereby improving ion transport efficiency. Compared to single-layer maicoene nanosheets, the maicoene nanosheets according to the embodiments of this application are easier to disperse in solution and less prone to recombination, more stable during processing and less prone to breakage or aggregation, and also exhibit better chemical stability, resisting oxidation and environmental degradation, thus having a longer service life.

[0045] Preferably, in the first embodiment of this application, the interlayer spacing of the maicoene nanosheets is 1.20 nm to 1.30 nm. Accordingly, the maicoene nanosheets have a larger interlayer spacing than maicoene obtained by conventional methods. This larger interlayer spacing prevents the recombination of maicoene nanosheets and reduces the hindrance to ion migration within the layers, thereby benefiting the application of maicoene nanosheets in electrochemical energy storage systems.

[0046] Preferably, in the first embodiment of this application, the titanium dioxide is a particle with an average diameter of 15 nanometers to 25 nanometers. Titanium dioxide particles with an average diameter in this range have a higher specific surface area, thereby providing more active sites and faster ion transport pathways in chemical or electrochemical reactions, and have better dispersibility and are less prone to agglomeration compared to particles that are too small.

[0047] Preferably, in the first embodiment of this application, the titanium dioxide is a single-crystal particle dispersed on the maicoene nanosheets. Correspondingly, compared to polycrystalline titanium dioxide particles, the titanium dioxide obtained by method 100 has fewer crystal defects, such as grain boundaries. In other words, the titanium dioxide has better crystallinity, i.e., a more ordered crystal structure, which can reduce ion diffusion resistance, increase ion diffusion rate, provide more active sites, enhance the reactivity of the material, and maintain a more stable crystal structure during chemical and electrochemical reactions. This reduces material breakage or pulverization caused by volume changes, and is beneficial for improving the performance of electrochemical energy storage systems, such as batteries.

[0048] According to a second embodiment of this application, this application provides a composite material for an electrochemical energy storage system, comprising: maicoene nanosheets, wherein the maicoene nanosheets have the chemical formula M n+1 AX n M is a transition metal element, A is a group III or group IV element, X is carbon or nitrogen, and n is 1, 2 or 3; and titanium dioxide particles dispersed on the maicoene nanosheets.

[0049] Electrochemical energy storage systems include, but are not limited to, lithium-ion batteries, sodium-ion batteries, lithium-sulfur batteries, and sodium-sulfur batteries.

[0050] Preferably, in the second embodiment of this application, the maicoene nanosheets are a material selected from the group consisting of Ti2AlC, Ti2SiC, Ti3SiC2, Ti3AlC2, and Ti4AlN3.

[0051] Preferably, in the second embodiment of this application, the number of layers of the maicoene nanosheets is 5 to 10.

[0052] Preferably, in the second embodiment of this application, the interlayer spacing of the maicoene nanosheets is 1.20 nanometers to 1.30 nanometers.

[0053] Preferably, in the second embodiment of this application, the titanium dioxide is a particle with an average diameter of 15 nanometers to 25 nanometers.

[0054] Preferably, in the second embodiment of this application, the titanium dioxide is a single crystal particle dispersed on the maicoene nanosheet.

[0055] According to a third embodiment of this application, a sodium-ion battery is provided. The sodium-ion battery comprises the composite material described above.

[0056] According to a fourth embodiment of this application, an energy storage system is provided. The sodium-ion battery comprises the composite material described above.

[0057] To facilitate a better understanding of the present invention, the following examples of specific embodiments are provided. These examples should not be construed as limiting or defining the entire scope of the invention. Those skilled in the art will recognize that the examples listed below are not an exhaustive list of embodiments of the present invention.

[0058] Example

[0059] 1. Introduction

[0060] The rapid rise in global energy demand due to population growth and economic interconnectivity has made efficient and environmentally friendly energy storage systems crucial. Faced with severe environmental challenges and the energy crisis, electrochemical systems such as rechargeable metal-ion batteries are essential for sustainable energy use in transportation, electronics, and grid applications. Extensive research has focused on advancing these energy storage technologies to meet modern needs. Notably, lithium-ion batteries (LIBs), as typical energy conversion and storage devices, are widely used in electric vehicles, mobile electronics, and other applications. However, due to the scarcity of lithium resources, LIBs are gradually losing their advantages in various consumer electronics and large-scale energy storage systems. Therefore, sodium-ion batteries (SIBs), due to their abundant reserves and cost-effectiveness, have attracted widespread attention as a promising alternative. Furthermore, the similar assembly methods and reaction mechanisms of LIBs and SIBs make SIBs compatible with most LIB production equipment, thus accelerating their development. However, sodium is heavier than lithium (23 g / mol). -1 vs. 6.9g mol -1 Its ionic radius is also larger than that of lithium. These differences result in low energy density, large volume changes, and sluggish kinetics in SIB solid-state electrodes, leading to unsatisfactory electrochemical performance. To address these issues, it is crucial to find suitable Na+ electrodes with sufficient reaction sites, excellent structural compatibility, and high stability. + The storage support material is crucial. Various SIB cathode materials have been extensively studied, including transition metal oxides, organic compounds, and Prussian blue and its analogues. However, finding anode materials with the high capacity and excellent stability required for SIBs remains a major obstacle to their development. For example, graphite, currently a commercially available anode material in LIBs, contains sodium... + Low mobility and drastic volume changes lead to poor rate performance and reduced cycle life of SIBs. Therefore, researchers are constantly exploring and developing novel anode materials for high-performance SIBs.

[0061] Over the past decade, two-dimensional (2D) materials, such as layered double hydroxides (LDHs), transition metal dichalcogenides (TMDs), black phosphorus, and transition metal carbides / nitrides (MXenes), have attracted widespread research interest in electrode applications due to their large reaction surfaces, efficient ion transport channels, and ease of intercalation and tunability. However, their applications remain limited by challenges such as insufficient interlayer spacing and severe layer aggregation. Therefore, setting up and constructing these 2D layered materials is crucial for positioning them as potential candidates for anodes in energy storage batteries (SIBs). Among these, MXenes have been developed into a class of versatile 2D materials with broad applicability in energy storage devices. The chemical formula of MXene is M... n+1 X n T x Where M represents a transition metal, X represents carbon and / or nitrogen, n = 1, 2 or 3, and T x These are mixed surface terminals, such as -OH, -O, or -F. MXenes have proven to be promising sodium storage anode materials due to their unique properties: excellent conductivity enables rapid electron transfer, transition metal oxide-like surfaces provide abundant active sites for rapid redox reactions, and tunable interlayer spacing facilitates the transfer of larger ions. Since MXenes were first reported in 2011, approximately 30 MXenes have been reported in the literature. Among MXenes, Ti3C2T... x Due to its metallic-like electrical conductivity (>10000 S cm⁻¹) -1 High theoretical sodium capacity (351.8 mAh g) -1 ) and surface low Na + The diffusion barrier (0.1 eV to 0.2 eV) has become a major focus of SIB research. However, similar to other 2D materials, pure Ti3C2T... x The anode is also subject to several inherent limitations: (1) conventionally synthesized multilayer Ti3C2T x (1) Due to the small interlayer spacing, the kinetic performance is poor and the capacity is low; (2) Due to the effects of van der Waals forces and hydrogen bonds, Ti3C2T x Nanosheets are prone to collapse and self-stacking, severely hindering the feasibility of ion diffusion pathways and the internal Na+. + Accessibility of adsorption sites leads to low capacity and rapid capacity decay; (3) Due to Ti3C2Tx It is usually manufactured by liquid phase etching under acidic conditions, and the thermodynamically metastable Ti atoms on its surface are easily oxidized; (4) The sodium ion storage capacity depends greatly on Ti3C2T x The surface functional groups, with inert end groups (-F and -OH), tend to reduce the diffusion and storage capacity of ions, while oxygen functional groups have good chemical reactivity and can promote the storage of sodium.

[0062] Therefore, it is desirable to develop a new synthesis strategy to precisely control TiO2 / Ti3C2T x The size and distribution of TiO2 nanoparticles in heterostructures are challenging to determine.

[0063] One example of this application employs a novel and simple sol-gel method to bond few-layer Ti3C2T x Nanosheets (f-Ti3C2T) x The UD-TiO2 nanoparticles were then assembled with in-situ formed TiO2 nanoparticles and calcined to create a heterostructure (UD-TiO2 / f-Ti3C2T). x The manufactured UD-TiO2 / f-Ti3C2T x The heterostructure contains ultradispersed anatase nanoparticles (~20 nm) and oligolayer Ti3C2T x The increased interlayer spacing in the middle is beneficial to enhancing Na + It adsorbs and promotes ion transfer. When used as the anode of SIB, UD-TiO2 / f-Ti3C2T x Heterogeneous structures at 0.02Ag -1 It can provide 190mAh g -1 It has excellent capacity and high long-cycle performance, at 2Ag -1 After 10,000 cycles, the capacity retention rate still reaches 92%. Experimental kinetic analysis and density functional theory (DFT) simulations show that UD-TiO2 / f-Ti3C2T... x Ion diffusion kinetics in heterostructures and Na + Adsorption was significantly improved. This application is for the development of a Ti3C2T-based adsorption technology for advanced SIBs. x This provides a new approach to heterogeneous structures.

[0064] 2. Testing Section

[0065] 2.1 Material Preparation

[0066] 2.1.1Ti3C2T x and oligolayer Ti3C2T x Synthesis of nanosheets

[0067] LiF (1.6 g, Admas) was dispersed in HCl (12 M, 20 mL, Chongqing Chuandong Chemical Co., Ltd., China) and stirred for 30 minutes. Then, 1 g of Ti3AlC2 powder (Jilin Yiyi Technology Co., Ltd., China) was added to the above solution and stirred at 45°C for 48 hours. The resulting residue was centrifuged and washed with deionized water (DI) until the pH of the supernatant reached approximately 5 to 6. Afterward, the initial Ti3C2T... x The solution was dispersed in 200 mL of deionized water under ice bath conditions, and then sonicated under an argon atmosphere for 1 hour. Subsequently, the suspension was centrifuged at 3500 rpm for 1 hour to collect the oligolayer Ti3C2T. x The supernatant was labeled as f-Ti3C2T x After freeze-drying, f-Ti3C2T was obtained. x powder.

[0068] 2.1.2. Ultradispersed TiO2 / Oligoplyl Ti3C2T x Synthesis of heterostructures and control samples

[0069] To synthesize ultradispersed TiO2 / oligolayer Ti3C2T x Heterogeneous structure (UDTiO2 / f-Ti3C2T) x ), 50 mg of f-Ti3C2T x Add to 200 mL of anhydrous ethanol (Greagent) and sonicate under argon pressure in an ice-water bath for 1 hour. Then, add a low concentration of concentrated ammonia (1 mL, ~28 wt%, Innochem) to f-Ti3C2T. x In an ethanol suspension, after stirring for 30 minutes, 3.5 mL of tetrabutyl titanate (TBOT, Sigma-Aldrich) was added dropwise to the solution. The mixture was kept under continuous stirring at room temperature for 24 hours. The calcined UDTiO2 / f-Ti3C2T was collected by centrifugation. x The material was washed with deionized water and then dried using a freeze-drying method. Finally, the dried material was calcined in 5% H2 / Ar at 500°C for 2 hours to obtain UD-TiO2 / f-Ti3C2T. x Heterogeneous structure. For comparison, f-Ti3C2T x The powder was also calcined in 5% H2 / Ar at 500℃ for 2 hours to obtain calcined f-Ti3C2T. x .

[0070] 2.2 Material Characterization

[0071] The microstructure and morphology of all samples were examined using scanning electron microscopy (SEM, ZEISS Gemini SEM300) and transmission electron microscopy (TEM, JEM-F200). X-ray powder diffraction (XRD, Bruker D8 with Cu Kα radiation) was performed to investigate the phase and crystal structure of the fabricated samples. Specific surface area was calculated using the Brunauer-Emmett-Teller (BET) method on an ASAP 2460 system. The surface chemical structure of all samples was analyzed using X-ray photoelectron spectroscopy (XPS, Thermo Scientific K-Alpha).

[0072] 2.3 Electrochemical Measurement

[0073] 80 wt% active material, 10 wt% carbon black (Super P), and 10 wt% polyvinylidene fluoride (PVDF) binder were mixed in N-methyl-2-pyrrolidone (NMP) to prepare a homogeneous slurry. The slurry was uniformly coated onto copper foil using a doctor blade and then dried overnight in a vacuum oven at 80°C. The dried electrode material was stamped into discs with a typical diameter of 12 mm. Assembly of the electrodes into a CR2032 type half-button cell was carried out in an argon-filled glove box, where O2 and H2O levels were maintained below 0.01 ppm. Sodium was used as the counter electrode. A 1.0 M NaClO4 solution in a 1:1 volume mixture of ethylene carbonate (EC) and propylene carbonate (PC) was used as the electrolyte, with glass fiber as the separator. Constant current discharge / charge characteristics were measured using a NEWARE multichannel battery testing system. Cyclic voltammetry (CV) curves were measured using a CHI660E electrochemical station. Measurements from 0.1 Hz to 10 Hz were measured using an AUTOLAB electrochemical station. 5 Electrochemical impedance spectroscopy (EIS) data in the Hz frequency range. At 0.01Ag -1The constant current condition was used for constant current intermittent titration (GITT) for 15 minutes, with a relaxation time of 1 hour.

[0074] 2.4. Calculation method:

[0075] Density functional theory (DFT) calculations were performed using the Perdew, Burke, and Ernzerhof (PBE) exchange correlation functions based on the generalized gradient approximation (GGA), implemented in the Vienna ab initio Simulation Package (VASP). The electron-ion interaction was described using the projector augmented wave (PAW) method, with plane wave cutoffs of 520 eV. Pure Ti3C2 was modeled using a supercell containing 120 atoms, with the vacuum region exceeding [a certain value]. ( Figure 12 Illustration a). For Ti3C2T x The structure, with functional groups (-F and -OH) located at the top and bottom of the intermediate Ti atoms ( Figure 12 Illustrations b and c). The TiO2(101) facet is modeled in six layers, containing 216 atoms and more. The vacuum region. Four of the six atomic layers are allowed to relax, while the remaining layers are confined within their bulk structure. 2×3 and 3×3 Monkhorst-Pack (MP) k-point meshes were used to model Ti3C2T. x Sampling was performed on the Brillouin zones of the TiO2(101) surface. The convergence criterion for the electronic self-consistent iteration was set to 10. -5 eV, and optimize atomic coordinates until the Hellmann-Feynman force is less than 100 kJ / m². VASPKIT, as a preprocessing and postprocessing tool for VASP, is used to prepare some input files.

[0076] 3. Results and Discussion

[0077] TiO2 / f-Ti3C2T x A schematic diagram of heterogeneous structure manufacturing is shown below. Figure 6 As shown. First, the Ti3AlC2MAX precursor was etched with LiF / HCl to obtain f-Ti3C2T. xNanosheets were formed and then ultrasonically treated to separate them into layers. Then, TiO2 nanoparticles were uniformly deposited onto f-Ti3C2T using a sol-gel method. x The nanosheets were then subjected to a final calcination treatment to obtain UD-TiO2 / f-Ti3C2T. x Heterogeneous structure. Similar to densely stacked Ti3AlC2 ( Figure 13 Illustrations a and b) and a typical accordion-shaped Ti3C2T x ( Figure 13 Compared to illustrations c and d), the f-Ti3C2T obtained by layering processing x Nanosheets have a large and flat surface. Figure 7A and Figure 7B TEM image ( Figure 7C This further revealed the morphology of the ultrathin nanosheets. After sol-gel and calcination treatment, a large number of TiO2 nanoparticles grew uniformly on the two-dimensional f-Ti3C2T x On nanosheets ( Figures 7D to 7F The obtained UD-TiO2 / f-Ti3C2T x The heterostructure successfully inherited the parent f-Ti3C2T x The nanosheets exhibit an ultrathin, sheet-like structure, containing neither aggregated nanosheets nor separated TiO2 nanoparticles. The size distribution of the TiO2 nanoparticles shows an average diameter of approximately 20 nm. Figure 7F ). Figure 7G Further demonstration of UD-TiO2 / f-Ti3C2T x The heterostructure consists of oligolayer nanosheets loaded with TiO2 nanoparticles. A well-defined lattice structure can be identified, with d-intervals of 0.35 nm and 0.26 nm, corresponding to the (101) plane of anatase TiO2 and Ti3C2T, respectively. x The (110) face. Meanwhile, the element distribution results ( Figure 7H The display shows that UD-TiO2 / f-Ti3C2T x The C, Ti and O elements are evenly distributed in the heterostructure.

[0078] Figure 8 Figure a shows the X-ray diffraction (XRD) pattern of the obtained sample. After the etching process, the peak corresponding to the MAX phase of Ti3AlC2 disappears, indicating successful removal of the Al layer and the formation of Ti3C2T... x The formation of Ti3C2T is noteworthy. It is important to note that after stratification, the Ti3C2T layer is related to the interlayer distance. x The (002) peak shifted from 7.7° (d = 1.15 nm) to 7.3° (d = 1.21 nm), which proves that the oligolayer Ti3C2T x The successful manufacturing of UD-TiO2 / f-Ti3C2T was achieved after sol-gel and calcination treatment.x The (002) peak in the heterostructure further shifted to 7.1°, indicating an increase in interlayer spacing to 1.25 nm. Meanwhile, in UD-TiO2 / f-Ti3C2T... x A new peak appears on the heterostructure curve at 25.4°, corresponding to the (101) plane of anatase TiO2 (JCPDF21-1272). These phenomena indicate that in f-Ti3C2T x TiO2 nanoparticles were formed in situ within the structure, with increased interlayer spacing, which could provide Na + The efficient transport and storage of ions creates more ion channels. Furthermore, Figure 14 Illustration a compares UD-TiO2 / f-Ti3C2T before and after calcination. x XRD patterns of the samples. As shown in the figure, after calcination, the (002) peak shifted to a larger angle. This shift can be attributed to the removal of end groups at high temperature, which resulted in a slight reduction in interlayer distance. f-Ti3C2T before and after calcination treatment. x A similar trend has also been observed in China. Figure 14 Illustration a). Figure 8 Illustration b shows UD-TiO2 / f-Ti3C2T x The BET specific surface area of ​​the heterostructure is 28.1 m². 2 g -1 Much larger than f-Ti3C2T x (10.1m 2 g -1 ) and Ti3C2T x (5.1m 2 g -1 In addition, UD-TiO2 / f-Ti3C2T x The average pore size distribution of the heterostructure is about 18 nm, however, in Ti3C2T x and f-Ti3C2T x Smaller pores of about 7nm were found in it, such as Figure 8 As shown in illustration c. UD-TiO2 / f-Ti3C2T x The increased specific surface area and mesoporous properties of heterostructures provide more active sites and promote electrolyte permeation. Surface species of the manufactured material were detected using X-ray photoelectron spectroscopy (XPS). For example, the spectral density was measured... Figure 14 As shown in illustration b), with the initial f-Ti3C2T x Compared to UD-TiO2 / f-Ti3C2T x The F intensity is lower and the O peak is larger in the heterostructure. (In the high-resolution F1s spectrum...) Figure 8In illustration d), the binding energies at 685.0 eV and 685.8 eV correspond to the F-Ti bond and the F-FC bond, respectively. The F content varies from f-Ti3C2T. x The concentration in UD-TiO2 / f-Ti3C2T decreased from 8.6 at.% to UD-TiO2 / f-Ti3C2T. x The 2.2 at.% concentration in the heterostructure indicates that most of the F groups have been removed. Meanwhile, pure f-Ti3C2T... x The O1s region of the nanosheets exhibits O-Ti and C-Ti-O bonds at 530.1 eV, 531.2 eV, 532.1 eV, and 533.3 eV, respectively. x Bond, C-Ti-(OH) x / C=O bond and CO peak ( Figure 8 Illustration e). In UD-TiO2 / f-Ti3C2T x In the heterostructure, a new peak appears at 529.0 eV, which is attributed to TiO2. Furthermore, as... Figure 8 As shown in illustration f, the initial f-Ti3C2T x The high-resolution Ti 2p spectrum can be fitted into three bimodal peaks, where Ti 2p 3 / 2 The peaks are located at 454.7 eV, 456.1 eV, and 457.7 eV, corresponding to C-Ti-C bonds, C-Ti-OH bonds, and C-Ti-O / F bonds, respectively, with C-Ti-OH species being the predominant surface group (approximately 30 at.%) (Table 1). In UD-TiO2 / f-Ti3C2T x In the heterostructure, the proportion of C-Ti-OH species decreases, and new Ti 2p... 3 / 2 The peak appears at 458.7 eV and is attributed to the Ti-O-Ti bond. Meanwhile, UD-TiO2 / f-Ti3C2T x The reduced C-Ti-C bond strength and shift to higher binding energies in the heterostructure confirm the migration of electrons from the C-Ti-C bonds to TiO2. These results indicate that UD-TiO2 / f-Ti3C2T x Successful construction of the heterostructure and the f-Ti3C2T process during synthesis x Effective removal of surface F groups.

[0079] Table 1. The proportion of Ti 2p peaks in the manufactured samples.

[0080] <![CDATA[UD-TiO2 / f-Ti3C2T x ]]> <![CDATA[f-Ti3C2T x ]]> C-Ti-C 25％ 61％ C-Ti-OH 27％ 30％ C-Ti-O / F 8％ 9％ Ti-O-Ti 40％ -

[0081] To evaluate the electrochemical performance, the fabricated material was used as the anode and metallic sodium as the counter electrode to produce Na. + Half battery. Figure 9A This shows UD-TiO2 / f-Ti3C2Tx The electrode is scanned at a rate of 0.1 mV / s. -1 The initial five cyclic voltammetry (CV) curves were obtained. In the first cathodic scan, several distinct peaks were resolved below 1.5 V, which can be attributed to the formation of the solid electrolyte interphase (SEI) layer and the accompanying irreversible reaction. In subsequent cycles, the overlap of the CV curves demonstrated the good electrochemical reversibility of the electrode during discharge / charge. These are consistent with pure f-Ti3C2T. x The CV curves of the electrodes are consistent, such as... Figure 15 As shown in illustration a. In fact, in UD-TiO2 / f-Ti3C2T x The absence of typical TiO2 redox peaks in the electrode indicates that Ti3C2T x Nanosheets contribute the most to capacity, while TiO2 mainly provides adsorption sites instead of directly participating in sodium storage.

[0082] UD-TiO2 / f-Ti3C2T x The electrode is at a current density of 0.02 Ag -1 0.05Ag -1 0.1Ag -1 0.2Ag -1 0.5Ag -1 1Ag -1 and 2Ag -1 Below, 190mAh g is presented respectively. -1 154mAhg -1 136mAhg -1 118mAhg -1 93mAhg -1 69mAhg -1 and 49mAhg -1 Reversible capacity ( Figure 9B and Figure 9C ). UDTiO2 / f-Ti3C2T x The electrode is at 0.02Ag. -1 The first discharge-charge curve under these conditions shows two irreversible plateau regions between 0.01V and 1.5V due to the formation of the SEI. Figure 9D This is consistent with the initial CV curve ( Figure 9A (Consistent). When the current density recovers to 0.02Ag -1 At that time, the reversible capacity remained at 163mAhg. -1 This retains 86% of the initial capacity. Figure 9B Conversely, f-Ti3C2T xThe electrode exhibits a much lower capacity at all current densities. Figure 9B and Figure 15 Illustration b). Furthermore, compared with the reported Ti3C2T x Compared to the base anode material, UD-TiO2 / f-Ti3C2T x The excellent electrochemical performance of the electrode proves that Ti3C2T x The good synergistic effect between TiO2 and sodium storage ( Figure 9E (and Table 2). Furthermore, Figure 9F and Figure 9G The cycling stability of the fabricated sample is shown. (Compared to f-Ti3C2T) x Compared to other electrodes, UD-TiO2 / f-Ti3C2T x The electrode is at 0.02Ag. -1 The capacity decay rate is relatively slow. Figures 9D to 9F and Figure 15 Illustration c). UD-TiO2 / f-Ti3C2T x The initial discharge capacity of the electrode is 376 mAh g. -1 The initial coulombic efficiency (ICE) is 43%, which is significantly higher than that of f-Ti3C2T. x Electrode (151mAh g) -1 (23%). It is important to emphasize that the cycling performance of SIBs at high current densities is a key parameter for practical applications. UD-TiO2 / f-Ti3C2T x Even at 2Ag -1 It still maintains a capacity of 45 mAh after 10,000 cycles. -1 Its excellent capacity maintains approximately 92% of its initial capacity. Figure 9G In comparison, f-Ti3C2T x The electrode was in 2Ag after 10,000 cycles. -1 Only 10mAh g was retained. -1 The lower capacity. Furthermore, Figure 15 Illustration d compares UD-TiO2 / f-Ti3C2T x UD-TiO2 / f-Ti3C2T before calcination x Rate capability of the electrode. UD-TiO2 / fTi3C2T at all current densities. x The electrode consistently exhibited a higher capacity than the uncalcined sample. This increased capacity highlights the crucial role of calcination in removing inert functional groups, thereby enhancing the capacity of the UD-TiO2 / f-Ti3C2T electrode. x Rate capability of the electrodes.

[0083] Table 2. Based on Ti3C2T x Performance comparison of different SIB anodes.

[0084]

[0085]

[0086] To further understand the enhanced electrochemical performance, the sodium storage mechanism and kinetics were tested. Figure 10 Illustration a and Figure 16 Illustration a shows UD-TiO2 / f-Ti3C2T at different scan rates, between 0.01V and 3V. x and f-Ti3C2T x The CV curves of the electrodes. As the scan rate increases, both the cathode and anode peaks gradually broaden. The current (i) and scan rate (v) follow a power-law relationship, as shown below:

[0087] i(V)=av b (1)

[0088] Where a and b are variable parameters. Sodium storage kinetics can be revealed by the b value, which is determined by the slope of log(i) versus log(v). A b value of 0.5 indicates a completely diffusion-controlled process, while a b value of 1.0 indicates completely capacitive storage. When calculating the cathodic b value over the entire operating potential window, due to UD-TiO2 / f-Ti3C2T x The b-value of the electrode is higher than that of f-Ti3C2T. x The b-value of the electrode, UD-TiO2 / f-Ti3C2T x The capacitor control characteristics are more obvious in it. Figure 10 Illustration b). This shows that even at higher current densities, UD-TiO2 / f-Ti3C2T x The cycling and rate performance of the electrode were also improved due to the faster kinetics achieved by the surface-confined reaction process. Furthermore, diffusion control and capacitance contribution can be quantified from the CV curves according to the following equation:

[0089] i(V)=k1v+k2v 1 / 2 (2)

[0090] Among them, k1v and k2v 1 / 2 These refer to capacitance contribution and diffusion contribution, respectively. Figure 10 Illustration c shows UD-TiO2 / f-Ti3C2T x Electrode and f-Ti3C2T x Calculated contribution ratio of the electrode. For UD-TiO2 / f-Ti3C2Tx Electrode and f-Ti3C2T x For both electrodes, the capacitance contribution rate gradually increases with increasing scan rate. At all scan rates, the UD-TiO2 / f-Ti3C2T... x The surface capacitance contribution in the electrode is higher than that in f-Ti3C2T x The surface capacitance contribution of the anode ultimately reaches 100 mV / s. -1 The yield reached 90%. UD-TiO2 / f-Ti3C2T x The main capacitance control characteristics in the electrode can be attributed to the abundance of active sites in the heterostructure, which is beneficial to Na + Rapid adsorption and accelerated reaction kinetics.

[0091] To further evaluate f-Ti3C2T x Electrode and UD-TiO2 / fTi3C2T x Electrochemical kinetics of the electrodes were investigated, and electrochemical impedance spectroscopy (EIS) was measured. Figure 16 Illustration b uses the equivalent circuit shown in the figure to depict the Nyquist plots and fitted lines of the two electrodes. In the equivalent circuit, R... s R represents the electrolyte resistance. ct It is a charge transfer resistance, and the Warburg impedance (W) is related to Na. + Related to diffusion. According to Table 3, it is related to f-Ti3C2T. x Compared to other electrodes, UD-TiO2 / f-Ti3C2T x The electrode has a small R ct The value indicates that the electrochemical kinetics have been improved. Furthermore, UDTiO2 / f-Ti3C2T x The higher Na content at the electrode + The diffusion coefficient implies faster ion transport kinetics. Figure 15 (See Illustration c and Table 3). Intermittent galvanostatic titration (GITT) is another effective method for evaluating sodium ion kinetics during discharge / charge. Figure 17 ). Figure 10 The illustration d shows f-Ti3C2T x Electrode and UD-TiO2 / f-Ti3C2T x GITT curves of the electrode during the first discharge / charge cycle. (Compared to f-Ti3C2T) x Compared to other electrodes, UD-TiO2 / f-Ti3C2T x The electrode exhibits a low overpotential and a long discharge-charge time, indicating that Na... + Diffusion resistance is reduced. Figure 10 Illustrations e and f show the relationship between f-Ti3C2Tx Compared to UD-TiO2 / f-Ti3C2T x Na of the electrode + The diffusion coefficient is high, which is consistent with the EIS results. This clearly demonstrates the effectiveness of UD-TiO2 / f-Ti3C2T. x The superior electrochemical kinetics of the electrode are characterized by a high capacitance contribution rate and increased Na+. + Diffusion coefficient.

[0092] Table 3. Impedance parameters obtained from the equivalent circuit model and f-Ti3C2T determined by GITT analysis. x Electrode and UD-TiO2 / f-Ti3C2T x Na of the electrode + diffusion coefficient

[0093]

[0094] Density functional theory (DFT) calculations were performed to elucidate the effect of surface TiO2 on sodium chemisorption. The adsorption energy of sodium on the material surface (Eadsorption energy) was calculated. ads The definition of ) is as follows:

[0095] E ads =(E Na / Material -nE Na -E Material ) / n (3)

[0096] Where E Na / Material It is the total energy on the material surface after sodium adsorption; E Na and E Material These represent the energy of a free sodium atom and the surface energy of the exposed material, respectively. n is the number of adsorbed sodium atoms. Figure 11 Illustrations a through d show the adsorption of sodium on different surfaces, including TiO2, bare Ti3C2, and F-terminated Ti3C2. The results indicate that the calculated Eadsorption of sodium on TiO2... ads The value is -2.69 eV, which means that the TiO2 surface is more favorable for sodium adsorption. Figure 11 (Illustration e). Furthermore, the chemical interaction of sodium with bare Ti3C2 (-2.00 eV) is stronger than its chemical interaction with saturated surfaces of -OH (-0.94 eV) and -F (-1.76 eV). Given the challenges of synthesizing bare Ti3C2, removing inert functional groups through post-treatment processes is a feasible and effective alternative to enhance Ti3C2T… x Sodium storage in the TiO2 / Ti3C2T layer. Therefore, by developing TiO2 / Ti3C2T... x Heterogeneous structure, introducing TiO2 and removing Ti3C2Tx The exposed inert functional groups contribute to the adsorption and storage of sodium.

[0097] In this application, in the oligolayer Ti3C2T x In-situ growth of ultradispersed TiO2 nanoparticles on nanosheets. After post-treatment and calcination, f-Ti3C2T x The inert F functional groups are removed. Under synergistic effects, UD-TiO2 / f-Ti3C2T x The heterostructure presents several advantages: First, the in-situ formed TiO2 nanoparticles are hyperdispersed in f-Ti3C2T x On nanosheets, as spacers, f-Ti3C2T is inhibited. x The re-stacking of f-Ti3C2T x The expanded interlayer spacing provides abundant reaction sites and can accommodate Na + The volume expansion caused by insertion. Furthermore, DFT calculations show that, compared to Ti3C2T... x In comparison, the stronger sodium adsorption energies on TiO2 and bare Ti3C2 are crucial for the rapid capacitively controlled sodium adsorption process. Therefore, UD-TiO2 / f-Ti3C2T x The heterostructure exhibits excellent rate performance and long-term cycling performance at 0.02 Ag. -1 It can provide 190mAh g -1 The capacity, even in 2Ag -1 Even after 10,000 cycles, it still maintains 92% capacity retention. This application opens up new possibilities for the structure and surface engineering of MXene-based electrodes in advanced SIBs.

[0098] Conventional hydrothermal oxidation methods result in inhomogeneous composite structures and agglomeration of titanium dioxide nanoparticles. These agglomerates are mainly located on the outer surface of maccene, making it difficult to achieve ultradispersion of nanoparticles between maccene layers. Furthermore, excessive oxidation passivates the active interfaces, which is detrimental to the electrical conductivity and electrochemical behavior of maccene. In method 100 provided in this application, titanium dioxide is composited with maccene in a controlled manner. The titanium dioxide nanoparticles not only act as interlayer spacers to prevent the recombination of maccene nanosheets but also promote the electrochemical activity of the heterostructure through the oxide surface of the titanium dioxide nanoparticles. Simultaneously, the composite process consumes exposed metastable titanium atoms, mitigating the chemical and structural degradation caused by the natural oxidation of maccene in ambient air.

[0099] Although embodiments of the invention have been shown and described, this application is not limited to those embodiments. Rather, those skilled in the art will understand that various modifications and changes can be made to the embodiments of the invention without departing from the scope of the invention, which is set forth in the claims.

Claims

1. A method for manufacturing a composite material, the method comprising: Macoene was fabricated into macoene nanosheets, wherein the macoene has the chemical formula M n+1 AX n In this system, M is a transition metal element, A is a group III or group IV element, X is a carbon or nitrogen element, and n is 1, 2, or 3. Titanium hydroxide was fabricated on the maicoene nanosheets; and The titanium hydroxide on the maicoene nanosheets is converted into titanium dioxide to form a composite material.

2. The method according to claim 1, characterized in that, The maicoene is a material selected from the group consisting of Ti2AlC, Ti2SiC, Ti3SiC2, Ti3AlC2, and Ti4AlN3.

3. The method according to claim 2, characterized in that, The process of fabricating macoene into macoene nanosheets includes: The maicoene was applied to a hydrogen chloride solution containing lithium fluoride to generate an intermediate product; The intermediate product was dispersed in deionized water in an ice bath and ultrasonically treated under a protective atmosphere to generate maicoene nanosheets.

4. The method according to claim 3, characterized in that, The weight ratio of lithium fluoride to maicoene is in the range of 1:0.65 to 1:

1.

5. The method of claim 4, further comprising, after forming maicoene into maicoene nanosheets, and before forming titanium hydroxide on the maicoene nanosheets: The maicoene nanosheets were immersed in anhydrous ethanol and suspended in an ice bath under a protective atmosphere.

6. The method according to claim 5, characterized in that, Titanium hydroxide is fabricated on the maicoene nanosheets by: Ammonia and a titanium source are applied to the suspension to generate titanium hydroxide on the maicoene nanosheets.

7. The method according to claim 6, characterized in that, The application of ammonia water causes the pH value to rise, thereby slowing down the hydrolysis of the titanium source.

8. The method according to claim 6, characterized in that, The application of ammonia water causes the metastable titanium atoms on the surface of the maicoene nanosheets to be consumed, and the metastable titanium atoms or the vacancies formed after they detach from the surface of the maicoene nanosheets serve as nucleation sites for the titanium hydroxide and the titanium dioxide.

9. The method according to claim 6, characterized in that, The titanium source is tetrabutyl titanate.

10. The method according to claim 6, characterized in that, Converting the titanium hydroxide on the maicoene nanosheets into titanium dioxide includes: The titanium hydroxide on the maicoene nanosheets is calcined to produce titanium dioxide.

11. The method according to claim 10, characterized in that, The number of layers in the maicoene nanosheets is 5 to 10.

12. The method according to claim 10, characterized in that, The interlayer spacing of the maicoene nanosheets is 1.20 nm to 1.30 nm.

13. The method according to claim 10, characterized in that, The titanium dioxide is a particle with an average diameter of 15 nanometers to 25 nanometers.

14. The method according to claim 13, characterized in that, The titanium dioxide is a single crystal particle dispersed on the maicoene nanosheet.

15. A composite material for an electrochemical energy storage system, comprising: Maicoene nanosheets, wherein the Maicoene nanosheets have the chemical formula M n+1 AX n Where M is a transition metal element, A is a Group 3 or Group 4 element, X is carbon or nitrogen, and n is 1, 2, or 3; and Titanium dioxide particles dispersed on the maicoene nanosheets.

16. The composite material according to claim 15, characterized in that, The maicoene nanosheets are selected from the group consisting of Ti2AlC, Ti2SiC, Ti3SiC2, Ti3AlC2, and Ti4AlN3.

17. The composite material according to claim 16, characterized in that, The number of layers in the maicoene nanosheets is 5 to 10.

18. The composite material according to claim 16, characterized in that, The interlayer spacing of the maicoene nanosheets is 1.20 nm to 1.30 nm.

19. The composite material according to claim 16, characterized in that, The titanium dioxide is a particle with an average diameter of 15 nanometers to 25 nanometers.

20. The composite material according to claim 19, characterized in that, The titanium dioxide is a single crystal particle dispersed on the maicoene nanosheet.

21. A sodium-ion battery comprising a composite material according to any one of claims 15 to 20.

22. An energy storage system comprising a composite material according to any one of claims 15 to 20.

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