Functionalized MXene / RGO composite material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of material preparation, and particularly discloses a functionalized MXene / RGO composite material as well as a preparation method and application thereof. According to the preparation method, reduction of graphene oxide and intercalation, functionalization and crystal face optimization of MXene are synchronously realized under the mediation of hydrazine hydrate through a one-step hydrothermal method, a three-dimensional conductive network taking reduced graphene oxide as a nano spacer is successfully constructed, the interlayer spacing of MXene is enlarged to 1.26 nm, the specific surface area reaches 107 m < 2 > / g, and the (002) crystal face orientation of MXene is remarkably optimized. The structure effectively solves the problems of easy stacking, slow ion transmission and poor cycling stability of MXene, shows high reversible capacity, excellent rate capability and outstanding cycling stability when being used as a sodium-ion battery negative electrode, and provides an advanced negative electrode material for development of a high-performance sodium-ion battery.

Description

Technical Field

[0001] This invention relates to the field of materials preparation technology, and in particular to a functionalized MXene / RGO composite material, its preparation method, and its application. Background Technology

[0002] With the escalating global energy crisis and environmental pollution, the development of novel energy storage devices that are efficient, low-cost, and have long cycle life has become a research hotspot in the energy field. Sodium-ion batteries (SIBs), due to the abundance and wide distribution of sodium resources, their low cost, and their similar electrochemical principles to lithium-ion batteries, are considered one of the most promising alternative technologies for large-scale energy storage systems and low-speed electric vehicles. As the core component of sodium-ion batteries, the electrochemical performance of the anode material directly determines the overall performance of the battery; therefore, developing high-performance sodium-ion battery anode materials is crucial for promoting the industrial application of SIBs.

[0003] Ti3C2T x MXene, as a typical representative of the two-dimensional transition metal carbide family, has shown great application potential in the field of sodium-ion battery anode materials due to its unique layered structure, excellent electronic conductivity, and tunable interlayer spacing. However, Ti3C2T... x MXene still faces many key technical challenges in its practical preparation and application in sodium-ion batteries, severely restricting its electrochemical performance and industrialization process. (Ti3C2T) x During the fabrication process, MXene nanosheets are prone to agglomeration and stacking, which obscures a large number of internal active surfaces. This significantly reduces the number of active sites that can actually participate in sodium ion adsorption and storage, preventing the full realization of their theoretical capacity advantage. Simultaneously, the agglomeration and stacking of the sheets leads to a reduction in the interlayer spacing of MXene, obstructing the diffusion channels of sodium ions between layers and lengthening the sodium ion diffusion path and electron transport distance, resulting in a decrease in ion diffusion coefficient and electron transport efficiency. Furthermore, the volume expansion and stress release generated during sodium ion insertion / extraction can easily cause the MXene sheet structure to collapse and peel off, thereby leading to a decline in the cycling performance of the electrode material.

[0004] Therefore, developing a method to effectively suppress MXene stacking, enhance its structural stability, and improve ion transport efficiency is crucial for advancing Ti3C2T. x The practical application of MXene-based materials in the field of sodium-ion battery anodes is of great significance. Summary of the Invention

[0005] For the existing Ti3C2T xMXene suffers from problems such as easy layer stacking, slow ion transport kinetics, and poor cycling stability. This invention provides a functionalized MXene / RGO composite material, its preparation method, and its applications. This invention utilizes a one-step hydrothermal method mediated by hydrazine hydrate in Ti3C2T... x Simultaneous introduction of reduced graphene oxide (RGO) into the interlayer of MXene to construct a three-dimensional conductive scaffold, and optimization of its (002) crystal orientation. This method effectively suppresses MXene stacking, accelerates ion / electron transport, and significantly improves the electrochemical performance of the material by enhancing sodium ion adsorption capacity.

[0006] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows: In a first aspect, the present invention provides a method for preparing a functionalized MXene / RGO composite material, comprising the following steps: Multilayer Ti3C2T x MXene and graphene oxide were dispersed in hydrazine hydrate and then subjected to a hydrothermal reaction at 150℃~200℃ under closed conditions. After solid-liquid separation and drying, functionalized MXene / RGO composite material was obtained.

[0007] Compared to existing technologies, the method for preparing functionalized MXene / RGO composite materials provided by this invention innovatively employs a one-step hydrothermal method, simultaneously achieving the reduction of graphene oxide (GO) and the construction of the MXene / RGO composite structure. In this process, hydrazine hydrate functions as both a reducing agent and a structure directing agent. During the hydrothermal reaction, hydrazine hydrate and the in-situ reduced graphene oxide (RGO) can be intercalated into the MXene layers, effectively suppressing the stacking of MXene sheets and increasing the interlayer spacing of MXene. Furthermore, the RGO within the MXene layers can form a stable three-dimensional conductive network. The increased interlayer spacing and the formation of the three-dimensional conductive network not only facilitate the exposure of more active sites but also provide spacious channels for ion transport, synergistically improving the electronic conductivity and ion diffusion rate of the material.

[0008] During the hydrothermal reaction, the interaction between hydrazine hydrate and MXene optimized its surface functional groups and, in conjunction with RGO, regulated the (002) crystal orientation of MXene. This microstructure optimization significantly enhanced the composite material's adsorption capacity for sodium ions, thereby fundamentally improving its electrochemical activity and laying the foundation for achieving high specific capacity. Furthermore, through the hydrothermal reaction under high temperature and pressure, MXene and RGO formed chemical bonds (such as CO-Ti bonds) and physical entanglement, making their bond stronger. This composite structure effectively buffered volume changes during charge and discharge, preventing the electrode material from pulverizing, thus significantly improving the cycle stability of sodium-ion batteries.

[0009] Furthermore, the multilayer Ti3C2T x The mass ratio of MXene to graphene oxide is (0.6~0.8):(0.15~0.25).

[0010] This ratio ensures that graphene oxide (GO) is completely reduced to RGO and can also be effectively inserted into the MXene interlayer as a nanospacer to construct a robust three-dimensional conductive network, thereby maximizing the suppression of MXene stacking, exposing active sites, and accelerating ion transport. At the same time, this ratio avoids the decrease in conductivity or blockage of ion transport pathways that may be caused by excessive GO, ensuring the dominant role of the high conductivity of MXene itself, and achieving an optimal balance between structural stability and electrochemical performance in the composite material.

[0011] Furthermore, the multilayer Ti3C2T x The mass-to-volume ratio of MXene to hydrazine hydrate is (0.6~0.8) g : (30~40) mL.

[0012] It should be noted that the hydrazine hydrate described in this invention is a commercially available product with a mass concentration of 80%.

[0013] The optimal amount of hydrazine hydrate not only provides a strong reducing environment for the full and rapid reduction of graphene oxide, ensuring its efficient conversion into highly conductive RGO; but also, the excess hydrazine hydrate protects Ti3C2T x Under high-temperature solvothermal conditions, it is not deeply oxidized into impurities such as TiO2, and it promotes the rearrangement of atoms in MXene, resulting in preferred orientation along the (002) crystal plane.

[0014] Furthermore, the hydrothermal reaction time is 18h to 24h.

[0015] The optimal reaction time ensures that graphene oxide can be fully reduced by hydrazine hydrate to highly conductive reduced graphene oxide (RGO), and that RGO nanosheets can be fully intercalated into the MXene layers, while also ensuring that hydrazine hydrate has sufficient time to functionalize the MXene surface and optimize its crystal orientation.

[0016] As a specific embodiment of the present invention, the multilayer Ti3C2T x The preparation method of MXene includes the following steps: Ti3AlC2 was added to hydrofluoric acid and etched at 25℃~45℃. After solid-liquid separation, washing, and drying, multilayer Ti3C2T was obtained. x MXene.

[0017] Furthermore, the mass-to-volume ratio of Ti3AlC2 to hydrofluoric acid is (1.8~3.2) g : (20~30) mL.

[0018] It should be noted that the hydrofluoric acid described in this invention is a commercially available product with a mass concentration of 48% to 51%.

[0019] Furthermore, the etching reaction takes 24 to 30 hours.

[0020] Specifically, after the etching reaction is complete, the sample is centrifuged, washed with deionized water until the pH of the supernatant is 6-7, and then dried to obtain a multilayer Ti3C2T. x MXene.

[0021] Secondly, the present invention also provides a functionalized MXene / RGO composite material, which is prepared by the preparation method of the functionalized MXene / RGO composite material described in any one of the above claims.

[0022] The functionalized MXene / RGO composite material prepared by the above method can have an interlayer spacing of MXene up to 1.26 nm and a specific surface area of ​​up to 107 m². 2 / g, and the (002) crystal orientation is significantly improved. The expanded interlayer spacing and high specific surface area not only provide a spacious diffusion channel and abundant active sites for the rapid insertion / extraction of sodium ions, significantly improving ion transport kinetics and reversible capacity; at the same time, the highly optimized (002) crystal orientation further enhances the adsorption and reactivity of the material for sodium ions. In addition, RGO, as an elastic support framework, effectively buffers the volume changes during charge and discharge, thus effectively improving the structural stability and cycle life of the composite electrode.

[0023] Thirdly, the present invention also provides a negative electrode comprising the above-described functionalized MXene / RGO composite material.

[0024] Fourthly, the present invention also provides a sodium-ion battery, including the aforementioned negative electrode.

[0025] Thanks to the (002) crystal plane optimization, expanded interlayer spacing, and stable three-dimensional conductive structure achieved during the hydrothermal process, the functionalized MXene / RGO composite material provided by this invention exhibits excellent sodium storage performance when used as a sodium-ion battery anode: at a current density of 50 mA / g, its reversible capacity reaches as high as 338 mAh / g; after 200 cycles, the capacity still remains at 260 mAh / g, demonstrating excellent cycle stability; even at a high current density of 5000 mA / g, the capacity can still be maintained at 97 mAh / g, significantly improving the overall performance of the sodium-ion battery. The functionalized MXene / RGO composite material prepared by this invention has significantly better overall performance than existing MXene-based anode materials, with a simple process and controllable cost, providing key material support for the development of next-generation high-performance, long-life sodium-ion batteries, and has important industrial application value. Attached Figure Description

[0026] Figure 1 The images show SEM images of the samples prepared in Example 1 and Comparative Example 3 of this invention, wherein (a) is the multilayer Ti3C2T prepared in Example 1. x (a) MXene, (b) HMX prepared in Comparative Example 3, (c) HMXene / RGO prepared in Example 1; Figure 2 These are TEM images of the samples prepared in Example 1 and Comparative Example 3 of the present invention, wherein (a) to (b) are multilayer Ti3C2T samples prepared in step a of Example 1 at different magnifications. x MXene, (c) to (d) are HMX samples prepared in Comparative Example 3 at different magnifications, and (e) to (f) are HMXene / RGO prepared in step b of Example 1; Figure 3 The XRD patterns are of the samples prepared in Example 1 and Comparative Examples 3-5 of this invention. Figure 4 The N2 adsorption-desorption isotherms are shown for the samples prepared in Example 1 and Comparative Example 3 of this invention. Figure 5 This is a comparison chart of the cycling performance of samples prepared in Example 1 and Comparative Examples 1-3 of the present invention; Figure 6 This is a comparison chart of the rate performance of the samples prepared in Example 1 and Comparative Examples 1-3 of the present invention. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0028] To better illustrate the present invention, further examples are provided below.

[0029] Materials used in the following examples: Titanium aluminum carbide (Ti3AlC2, 400 mesh) was purchased from Jilin Yiyi Technology Co., Ltd.; hydrofluoric acid (HF, 48.0~51.0 wt%) was purchased from Hebei Bailingwei Ultrafine Materials Co., Ltd.; hydrazine hydrate (N2H4·H2O, 80%) was purchased from Aladdin; hydroxylamine hydrochloride (H3NO·HCl) was purchased from Shandong Keyuan Biochemical Co., Ltd.; hydrazine sulfate (N2H4·H2SO4) was purchased from Shandong Keyuan Biochemical Co., Ltd.; sodium hydroxide (NaOH) was purchased from Tianjin Damao Chemical Reagent Factory; graphene oxide (GO, 10 mg / g) was purchased from Hangzhou Gaoxi Technology Co., Ltd.; carbon black and polytetrafluoroethylene (PVDF) were purchased from Guangdong Zhuguang New Energy Technology Co., Ltd.; N-methylpyrrolidone (NMP) was purchased from Tianjin Damao Chemical Reagent Factory; NaClO4 electrolyte (1 M NaClO4 is dissolved in ethylene carbonate (EC) and propylene carbonate (PC) in a volume ratio of 1:1, and contains 5% by volume of fluoroethylene carbonate (FEC) as an additive.

[0030] Example 1 This embodiment provides a method for preparing a functionalized MXene / RGO composite material, including the following steps: Step a: Slowly add 2g of Ti3AlC2 powder to 25mL of hydrofluoric acid, and react with magnetic stirring at 35℃ for 24h. After the reaction is complete, centrifuge and wash until the pH of the supernatant is 6-7, then dry to obtain multilayer Ti3C2T x MXene; Step b, 0.7g of the multilayer Ti3C2T prepared above... x MXene and 0.2 g of graphene oxide (GO) were added to a PTFE container containing 35 mL of hydrazine hydrate, stirred evenly, sealed, and reacted in a muffle furnace at 180 °C for 20 h. After centrifugation, washing, and drying, functionalized MXene / RGO composite material was obtained, denoted as HMXene / RGO.

[0031] Example 2 This embodiment provides a method for preparing a functionalized MXene / RGO composite material, including the following steps: Step a: Slowly add 1.8g of Ti3AlC2 powder to 20mL of hydrofluoric acid, and react with magnetic stirring at 45℃ for 24h. After the reaction is complete, centrifuge and wash until the pH of the supernatant is 6-7, then dry to obtain multilayer Ti3C2T x MXene; Step b, add 0.6g of the multilayer Ti3C2T prepared above.x MXene and 0.15 g of graphene oxide (GO) were added to a PTFE container containing 30 mL of hydrazine hydrate, stirred evenly, sealed, and reacted in a muffle furnace at 200 °C for 18 h. After centrifugation, washing, and drying, functionalized MXene / RGO composite material was obtained, denoted as HMXene / RGO.

[0032] Example 3 This embodiment provides a method for preparing a functionalized MXene / RGO composite material, including the following steps: Step a: Slowly add 3.2g of Ti3AlC2 powder to 30mL of hydrofluoric acid, and react with magnetic stirring at 25℃ for 30h. After the reaction is complete, centrifuge and wash until the pH of the supernatant is 6-7, then dry to obtain multilayer Ti3C2T x MXene; Step b, add 0.8g of the multilayer Ti3C2T prepared above. x MXene and 0.25 g of graphene oxide (GO) were added to a PTFE container containing 40 mL of hydrazine hydrate, stirred evenly, sealed, and reacted in a muffle furnace at 150 °C for 24 h. After centrifugation, washing, and drying, functionalized MXene / RGO composite material was obtained, denoted as HMXene / RGO.

[0033] Comparative Example 1 This comparative example provides a method for preparing HSMX / RGO, including the following steps: Step a: Slowly add 2g of Ti3AlC2 powder to 25mL of hydrofluoric acid, and react with magnetic stirring at 35℃ for 24h. After the reaction is complete, centrifuge and wash until the pH of the supernatant is 6-7, then dry to obtain multilayer Ti3C2T x MXene; Step b: Dissolve 1.5g of sodium hydroxide in 30mL of deionized water, add 0.5g of hydrazine sulfate (N2H4·H2SO4) to obtain a hydrazine sulfate solution; 0.7g of the multilayer Ti3C2T prepared above was used. x MXene and 0.2 g of graphene oxide (GO) were added to a PTFE container containing the above hydrazine sulfate solution, stirred evenly, sealed, and reacted in a muffle furnace at 180 °C for 20 h. After centrifugation, washing, and drying, HSMX / RGO was obtained.

[0034] Comparative Example 2 This comparative example provides a method for preparing HHMX / RGO, including the following steps: Step a: Slowly add 2g of Ti3AlC2 powder to 25mL of hydrofluoric acid, and react with magnetic stirring at 35℃ for 24h. After the reaction is complete, centrifuge and wash until the pH of the supernatant is 6-7, then dry to obtain multilayer Ti3C2T x MXene; Step b: Dissolve 0.5g of hydroxylamine hydrochloride (H3NO·HCl) in 30mL of deionized water to obtain hydrazine hydrochloride solution; 0.7g of the multilayer Ti3C2T prepared above was used. x MXene and 0.2 g of graphene oxide (GO) were added to a PTFE container containing the prepared hydrazine hydrochloride solution, stirred evenly, sealed, and reacted in a muffle furnace at 180 °C for 20 h. After centrifugation, washing, and drying, HHMX / RGO was obtained.

[0035] Comparative Example 3 This comparative example provides a method for preparing HMX, including the following steps: Step a: Slowly add 2g of Ti3AlC2 powder to 25mL of hydrofluoric acid, and react with magnetic stirring at 35℃ for 24h. After the reaction is complete, centrifuge and wash until the pH of the supernatant is 6-7, then dry to obtain multilayer Ti3C2T x MXene; Step b, 0.7g of the multilayer Ti3C2T prepared above... x MXene was added to a PTFE container containing 35 mL of hydrazine hydrate, stirred until homogeneous, sealed, and reacted in a muffle furnace at 180 °C for 20 h. After centrifugation, washing, and drying, the HMX sample was obtained.

[0036] Comparative Example 4 This comparative example provides a method for preparing HSMX, including the following steps: Step a: Slowly add 2g of Ti3AlC2 powder to 25mL of hydrofluoric acid, and react with magnetic stirring at 35℃ for 24h. After the reaction is complete, centrifuge and wash until the pH of the supernatant is 6-7, then dry to obtain multilayer Ti3C2T x MXene; Step b: Dissolve 1.5g of sodium hydroxide in 30mL of deionized water, add 0.5g of hydrazine sulfate (N2H4·H2SO4) to obtain a hydrazine sulfate solution; 0.7g of the multilayer Ti3C2T prepared above was used. x MXene was added to a PTFE container containing the above-mentioned hydrazine sulfate solution, stirred evenly, sealed, and reacted in a muffle furnace at 180°C for 20 hours. After centrifugation, washing, and drying, the HSMX sample was obtained.

[0037] Comparative Example 5 This comparative example provides a method for preparing HHMX, including the following steps: Step a: Slowly add 2g of Ti3AlC2 powder to 25mL of hydrofluoric acid, and react with magnetic stirring at 35℃ for 24h. After the reaction is complete, centrifuge and wash until the pH of the supernatant is 6-7, then dry to obtain multilayer Ti3C2T x MXene; Step b: Dissolve 0.5g of hydroxylamine hydrochloride (H3NO·HCl) in 30mL of deionized water to obtain hydrazine hydrochloride solution; 0.7g of the multilayer Ti3C2T prepared above was used. x MXene was added to a PTFE container containing the prepared hydrazine hydrochloride solution, stirred until homogeneous, sealed, and reacted in a muffle furnace at 180°C for 20 h. After centrifugation, washing, and drying, the HHMX sample was obtained.

[0038] Material characterization The microstructure and morphology of the samples were analyzed using field emission transmission electron microscopy (FE-TEM, JEOL JEM-2100F, JP) and field emission scanning electron microscopy (FE-SEM, Hitachi S-4800, JP). Figures 1-2 As shown.

[0039] Figure 1 (a) The multilayer Ti3C2T prepared in step a of Example 1 x The SEM image of MXene shows that it exhibits a typical multi-layered accordion structure. Figure 1 (b) is a SEM image of the HMX sample prepared in Comparative Example 3. As can be seen from the image, compared to the multilayer Ti3C2T sample in Example 1... x After undergoing a hydrothermal reaction with hydrazine hydrate, the interlamellar spacing of MXene increases to some extent. Figure 1 (c) is a SEM image of HMXene / RGO prepared in Example 1. As can be seen from the image, wrinkled RGO nanosheets are attached to the MXene surface, proving that an RGO intercalated MXene structure has been formed.

[0040] Figure 2 (a) to (b) show the multilayer Ti3C2T prepared in step a of Example 1 at different magnifications. x TEM images of MXene: (c) to (d) are TEM images of the HMX sample prepared in Comparative Example 3 at different magnifications; (e) to (f) are TEM images of the HMXene / RGO prepared in step b of Example 1. Multilayer Ti3C2T prepared in step a of Example 1. xThe interlayer spacing of MXene is about 1.064 nm. After hydrothermal treatment with hydrazine hydrate, the interlayer spacing of MXene in Comparative Example 3 can reach 1.162 nm. Furthermore, after introducing RGO, the interlayer spacing of HMXene is further increased to 1.26 nm.

[0041] The crystal structure was determined by X-ray diffraction (XRD, RigakuD / max-2500). Figure 3 The images show the XRD patterns of the samples prepared in Example 1 and Comparative Examples 3-5 of this invention.

[0042] As can be seen from the figure, after solvothermal treatment with hydrazine hydrate, no characteristic peaks of TiO2 were found in the XRD patterns of HMX and HMXene / RGO, indicating that hydrazine hydrate can still protect Ti3C2T at higher temperatures. x MXene prevents oxidation.

[0043] MXene (002) crystal plane analysis: The diffraction peaks corresponding to the MXene (002) crystal planes are all shifted to lower angles. This is due to the intercalation and pillaring effect of hydrazine hydrate between MXene layers during the solvothermal process. The degree of MXene (002) crystal plane shift indicates that the control of the MXene (002) crystal plane using hydrazine hydrochloride and hydrazine sulfate is far less effective than that using hydrazine hydrate. Compared with the multilayer Ti3C2T prepared in step a of Example 1... x Compared to MXene, the relative intensity ratio I(002) / I(110) of the (002) peak to the (110) peak of HMX is significantly improved. The diffraction peaks of the HMX (002) crystal plane are also significantly improved compared to those of multilayer Ti3C2T. x The significant enhancement of MXene indicates that HMX, after treatment with hydrazine hydrate, possesses a good layered structure and highly plane-preferred orientation along the (002) crystal plane. The addition of RGO further increases the relative intensity ratio of HMXene / RGO, I(002) / I(110), suggesting a further improvement in crystal plane orientation.

[0044] Nitrogen adsorption-desorption tests were performed at 77 K using a nitrogen adsorption-desorption analyzer (Amercian Micromeritics ASAP2020, USA). The specific surface area of ​​the samples was calculated using the Brunauer-Emmett-Teller (BET) method. The results are as follows: Figure 4 As shown.

[0045] according to Figure 4 The N2 adsorption-desorption isotherm test showed that the specific surface area of ​​HMX prepared in Comparative Example 3 was 9 m². 2 / g, the specific surface area of ​​HMXene / RGO prepared in Example 1 is 107 m² / g. 2 / g. This indicates that the intercalation of RGO effectively increases the specific surface area of ​​MXene. This large specific surface area provides abundant active sites for the adsorption and conversion of sodium ions, which is beneficial to improving the sodium storage capacity of the material. On the other hand, it constructs a continuous and rapid ion transport channel, which significantly improves the reaction kinetics. In addition, the structure has excellent mechanical stability and is not easy to collapse during cycling, ensuring the long-term durability of sodium storage capacity.

[0046] Performance testing Preparation of negative electrode: The HMXene / RGO, carbon black and PVDF prepared in Example 1 were dispersed in N-methylpyrrolidone solution (NMP) at a mass ratio of 8:1:1 and stirred for more than 30 minutes until fully mixed. The mixture was coated on copper foil and dried at 60°C for 12 hours to obtain MXene / RGO electrode sheet.

[0047] Assemble the button cell: Using the MXene / RGO electrode prepared above as the negative electrode, NaClO4 as the electrolyte, and a Na sheet as the positive electrode, assemble the button cell in the following order: negative electrode shell – positive electrode – electrolyte – separator – electrolyte – negative electrode – gasket – spring sheet – positive electrode shell. Prepare the negative electrode of other materials using the same method as above and assemble them into a button cell.

[0048] Cyclic performance: Cyclic performance was tested using a battery testing system (Neware) at a current density of 50 mA / g and a voltage range of 0.01–2.5V. The cycle consisted of discharging to 0.01V and then charging to 2.5V, constituting one cycle, with 200 cycles performed. Results are as follows: Figure 5 As shown in Table 1.

[0049] Table 1 Cyclic Performance

[0050] At a current density of 50 mA / g, the HMXene / RGO electrode prepared in Example 1 exhibited an initial reversible capacity of 338 mAh / g, an improvement over HMX (149 mAh / g). After 200 cycles, the HMXene / RGO prepared in Example 1 maintained a stable capacity of 260 mAh / g with a coulombic efficiency close to 100%. In contrast, the initial reversible capacity of HSMXene / RGO prepared in Comparative Example 1 was 210 mAh / g, and that of HHMXene / RGO prepared in Comparative Example 2 was 157 mAh / g. The initial reversible capacities of Comparative Examples 1 and 2 were significantly lower than those of HMXene / RGO in Example 1. This demonstrates that the performance of MXene treated with hydrazine sulfate and hydrazine hydrochloride is far inferior to that treated with hydrazine hydrate.

[0051] Rate performance: Rate performance was tested at current densities of 50 mA / g, 100 mA / g, 200 mA / g, 500 mA / g, 1000 mA / g, 2000 mA / g, and 5000 mA / g. The test involved discharging to 0.01V and then charging to 2.5V at a current density of 50 mA / g, repeated 10 times. Then, the same process was repeated at a current density of 100 mA / g, discharging to 0.01V and charging to 2.5V, repeated 10 times. This continued until the threshold current density of 5000 mA / g was reached, where the voltage was discharged to 0.01V and charged to 2.5V, repeated 10 times. Finally, the test returned to a current density of 50 mA / g, discharging to 0.01V and charging to 2.5V, repeated 20 times, ending the test. The results are as follows: Figure 6 As shown in Table 2.

[0052] Table 2. Specific capacity (mAh / g) at different current densities

[0053] The results show that the HMXene / RGO electrode exhibits higher specific capacities than other comparative samples at current densities of 50 mA / g, 100 mA / g, 200 mA / g, 500 mA / g, 1000 mA / g, 2000 mA / g, and 5000 mA / g. Even at an ultra-high current density of 5000 mA / g, it still provides a capacity of 97 mAh / g. When the current density returns to 50 mA / g, the specific capacity recovers rapidly, indicating that its structure has excellent stability.

[0054] In summary, this invention achieves simultaneous reduction of graphene oxide and intercalation, functionalization, and crystal facet optimization of MXene via a one-step hydrothermal method mediated by hydrazine hydrate. This successfully constructs a three-dimensional conductive network using reduced graphene oxide as nanospacers, increasing the MXene interlayer spacing to 1.26 nm and achieving a specific surface area of ​​10⁷ m². 2 / g, and significantly optimized its (002) crystal orientation. This structure effectively solves the problems of easy stacking, slow ion transport and poor cycle stability of MXene. When used as a negative electrode for sodium-ion batteries, it exhibits a high reversible capacity of 338 mAh / g, excellent rate performance (maintaining 97 mAh / g at 5000 mA / g), and outstanding cycle stability (capacity maintained at 260 mAh / g after 200 cycles), providing an advanced negative electrode material for the development of high-performance sodium-ion batteries.

[0055] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a functionalized MXene / RGO composite material, characterized in that, Includes the following steps: Multilayer Ti3C2T x MXene and graphene oxide were dispersed in hydrazine hydrate and then subjected to a hydrothermal reaction at 150℃~200℃ under closed conditions. After solid-liquid separation and drying, functionalized MXene / RGO composite material was obtained.

2. The method for preparing the functionalized MXene / RGO composite material as described in claim 1, characterized in that, The multilayer Ti3C2T x The mass ratio of MXene to graphene oxide is (0.6~0.8):(0.15~0.25).

3. The method for preparing the functionalized MXene / RGO composite material as described in claim 1, characterized in that, The multilayer Ti3C2T x The mass-to-volume ratio of MXene to hydrazine hydrate is (0.6~0.8) g : (30~40) mL.

4. The method for preparing the functionalized MXene / RGO composite material as described in claim 1, characterized in that, The hydrothermal reaction time is 18h to 24h.

5. The method for preparing the functionalized MXene / RGO composite material as described in claim 1, characterized in that, The multilayer Ti3C2T x The preparation method of MXene includes the following steps: Ti3AlC2 was added to hydrofluoric acid and etched at 25℃~45℃. After solid-liquid separation, washing, and drying, multilayer Ti3C2T was obtained. x MXene.

6. The method for preparing the functionalized MXene / RGO composite material as described in claim 5, characterized in that, The mass-to-volume ratio of Ti3AlC2 to hydrofluoric acid is (1.8~3.2) g : (20~30) mL.

7. The method for preparing the functionalized MXene / RGO composite material as described in claim 5, characterized in that, The etching reaction takes 24 to 30 hours.

8. A functionalized MXene / RGO composite material, characterized in that, It is prepared by the method for preparing the functionalized MXene / RGO composite material according to any one of claims 1 to 7.

9. A negative electrode, characterized in that, Includes the functionalized MXene / RGO composite material as described in claim 8.

10. A sodium-ion battery, characterized in that, Includes the negative electrode as described in claim 9.

Images