Three-dimensional porous MXene derived heterojunction material, composite material and preparation method
By preparing three-dimensional porous MXene-derived heterojunction materials, the problems of polysulfide shuttle effect and MXene layer aggregation in lithium-sulfur batteries were solved, achieving high conductivity and stability, simplifying the preparation process, and making it suitable for mass production.
Patent Information
- Application Number
- CN202511731178.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-24
- Publication Date
- 2026-02-17
AI Technical Summary
Existing lithium-sulfur batteries suffer from problems such as polysulfide shuttle effect, low utilization of active materials, and poor cycle performance. In existing technologies, the aggregation and overlap of MXene layers prevent the full utilization of functional surfaces and catalytic activity, and the preparation methods are complex and not conducive to mass production.
Few-layer or single-layer MXene dispersions were prepared by etching and mechanical exfoliation. Combined with ferric nitrate hexahydrate and sulfonated polystyrene spheres, three-dimensional porous MXene-derived heterojunction materials were formed by spray drying and heat treatment. The heterojunctions were constructed using Ti source to form a three-dimensional carbon framework, thus avoiding MXene oxidation.
It achieves conductivity and stability of a three-dimensional carbon framework, suppresses polysulfide shuttle effect, simplifies preparation steps, improves battery conductivity and cycle stability, and is suitable for mass production.
Smart Images
Figure CN121546064A_ABST
Abstract
Description
Technical Field
[0002] This invention relates to the field of lithium-sulfur battery materials and processing technology, and in particular to three-dimensional porous MXene-derived heterojunction materials, composite materials and preparation methods. Background Technology
[0004] MXenes are two-dimensional layered materials derived from transition metal carbides, nitrides, or carbonitrides (such as Ti3C2), providing both excellent conductivity and abundant polar functional surfaces. Unlike graphene and phosphorene, which have natural 3D precursors of graphite and black phosphorus, respectively, MXenes do not have direct 3D precursors in nature. Instead, MXene multilayer sheets are typically produced by selectively removing the A layer from the MAX phase, for example, removing Al from Ti3AlC2. Therefore, MXene nanosheets can be readily obtained after layering using intercalators such as DMSO and LiF. Due to their unique properties, including excellent mechanical properties, high conductivity, abundant surface chemistry, and convenient processability, MXenes are currently widely used in rechargeable battery electrodes, supercapacitors, and catalysts.
[0005] Among them, alkali metal-sulfur secondary batteries (Li-S, Na-S, etc.) with high energy density are considered to be highly promising economical energy storage systems. However, these batteries suffer from problems such as polysulfide shuttle, leading to low utilization of active materials and poor cycle performance, which cannot meet the requirements of large-scale energy storage and electric vehicles. Taking lithium-sulfur batteries as an example, the electrical insulation properties of the active material (S) and the final product (Li2S) and the volume change (80%) between sulfur and the final product during the electrochemical process make it difficult to improve the battery discharge capacity and the electrode structure is unstable. In addition, long-chain lithium polysulfides (LiPSs, Li2S) n Lithium (4≤n≤8) readily dissolves in electrolytes, leading to a severe "shuttle effect," resulting in low sulfur utilization, corrosion of metallic lithium, coulombic efficiency issues, and rapid capacity decay, thus limiting its application. Effectively addressing these challenges and developing high-performance electrode materials is crucial for the development of lithium-sulfur batteries. While electrolyte optimization, intermediate layers, or adsorbents can suppress the "shuttle effect" to some extent and improve the cycling stability of sulfur, these methods typically result in high costs and low battery energy density.
[0006] Due to the differences in redox kinetics and the complex phase transition of sulfur, single-component catalysts cannot continuously accelerate the entire redox process. Designing heterojunctions can combine the advantages of different materials, effectively adjust the electronic structure, improve electrochemical affinity, and accelerate the conversion kinetics of polysulfides. Typically, heterostructures consist of two or more materials. Due to the unique physical and chemical properties of different materials, heterostructures can exhibit superior performance that cannot be achieved by a single material at a homogeneous interface. Electron conduction at the heterostructure interface further accelerates the conversion of polysulfides, thus avoiding the accumulation of long-chain polysulfides. This not only enhances the reaction kinetics but also further avoids the shuttle effect, ultimately achieving good cycle stability and high discharge capacity. However, the unique structure of heterostructures and the regulation of the electronic structure of heterostructure interfaces remain challenges for high-performance lithium-sulfur batteries.
[0007] MXene, as a representative two-dimensional layered material, possesses excellent conductivity, a large polar surface area, and abundant active sites. To date, the incorporation of MXene-based heterostructures (such as Ti3C2 / MnO2, TiO2-MXene, and VO2-V2C) into electrodes / separators has been considered an effective method for simultaneously regulating lithium insertion / extraction in Li-S batteries and accelerating the multi-electron redox kinetics at the sulfur interface. However, due to strong van der Waals forces, the aggregation and overlap of MXene layers can lead to insufficient utilization of their functional surface area and catalytic activity. Furthermore, existing technologies often require avoiding MXene oxidation, resulting in cumbersome preparation methods. In addition, existing technologies typically employ hydrothermal reactions, which involve high temperature and pressure, poor safety performance, and are not conducive to mass production. Summary of the Invention
[0009] Purpose of the invention: The purpose of this invention is to provide a three-dimensional porous MXene-derived heterojunction material, composite material, and preparation method, which can solve the problems in the prior art.
[0010] Technical solution: The preparation method of the three-dimensional porous MXene-derived heterojunction material of the present invention includes the following steps:
[0011] S1: The Al layer was peeled off from Ti3AlC2 powder by etching, and then a few-layer or monolayer MXene dispersion was obtained by mechanical exfoliation.
[0012] S2: Disperse ferric nitrate hexahydrate in the MXene dispersion obtained in step S1 to obtain the first dispersion; disperse sulfonated polystyrene spheres in anhydrous ethanol and ultrasonically disperse them evenly to obtain the second dispersion;
[0013] S3: The second dispersion is slowly added to the first dispersion and stirred evenly. The resulting mixed solution is then introduced into a spray drying device and dried to obtain the precursor material.
[0014] S4: The precursor material obtained in step S3 is heat-treated in an inert atmosphere, and then heat-treated in ammonia to finally obtain a three-dimensional porous MXene-derived heterojunction material. In this way, the template can be removed by heat treatment in an inert atmosphere to obtain microsphere clusters composed of hollow spherical particles; and then the nitride heterojunction derived in situ from MXene can be obtained by heat treatment in ammonia.
[0015] Furthermore, the mechanical exfoliation method in step S1 involves ultrasonication at a temperature of 18-24°C for 4-6 hours. Controlling the temperature ensures that MXene is not oxidized during the mechanical exfoliation process, thus preventing damage to the anionic functional groups on the surface and facilitating subsequent electrostatic adsorption of cations. Prolonged ultrasonic treatment allows for the mechanical exfoliation of thick MXene layers, resulting in few-layer or monolayer MXene dispersions.
[0016] Furthermore, in step S2, the concentration of sulfonated polystyrene spheres in the second dispersion is 1.25 wt%.
[0017] Further, in step S1, the MXene concentration is 3-5 mg / mL; the mass ratio of MXene to sulfonated polystyrene spheres is 1:1.6-1:1.8; and the mass ratio of MXene to ferric nitrate hexahydrate is 1:0.8-1:2.6. The content of sulfonated polystyrene spheres needs to be controlled: if the content is too high, MXene will not be able to completely coat the microspheres, resulting in broken MXene spheres on the surface of the final product microspheres; if the content is too low, excessive MXene will cause the final product to shrivel and fail to form a regular spherical shape.
[0018] Furthermore, in step S4, the heat treatment temperature in the inert atmosphere is 200~800℃, and the heat treatment time is 1~4 h; the heat treatment temperature in the ammonia gas is 200~800℃, and the heat treatment time is 1~4 h.
[0019] Furthermore, in step S4, the heat treatment in an inert atmosphere involves preheating at 200-300°C for 1-2 hours, and then raising the temperature to 600-800°C and holding for 2-4 hours.
[0020] Furthermore, in step S4, the heat treatment in the inert atmosphere involves preheating at 250°C for 1-2 hours, and then raising the temperature to 750°C and holding for 2-4 hours.
[0021] Furthermore, in step S4, the heat treatment in ammonia is performed by holding the ammonia at 750°C for 2 hours.
[0022] The present invention also discloses a three-dimensional porous MXene-derived heterojunction material prepared by the aforementioned preparation method.
[0023] The sulfur-three-dimensional porous MXene-derived heterojunction composite material of the present invention is composed of the aforementioned three-dimensional porous MXene-derived heterojunction material and sulfur.
[0024] Beneficial effects: This invention discloses a three-dimensional porous MXene-derived heterostructure material, composite material, and preparation method, which have the following beneficial effects compared with the prior art:
[0025] 1. The three-dimensional porous MXene-derived heterojunction material prepared by this invention possesses a three-dimensional carbon framework, effectively solving the problem of "MXene layer aggregation and overlap" in existing technologies, and exhibits excellent conductivity and stability. Specifically, the conductivity is enhanced because the three-dimensional carbon framework provides excellent electron and ion diffusion channels for electrochemical reactions, shortening the ion diffusion distance and thus reducing the internal resistance of the battery. This facilitates the transfer of electrons and ions between the electrolyte and electrode materials.
[0026] 2. The three-dimensional porous MXene-derived heterojunction material prepared by this invention has abundant pore structure and three-dimensional structure, which is beneficial for sulfur loading. Furthermore, as a sulfur carrier, the in-situ MXene-derived heterostructure within the material ensures a uniform distribution of catalytic sites, and the hierarchical pore structure can suppress the shuttle effect of polysulfides through physicochemical means.
[0027] 3. The principle of this invention is completely different from that of existing technologies. Existing technologies aim to fully utilize the various properties of MXene, thus requiring consideration of minimizing MXene oxidation during the preparation process. This invention, however, only needs to utilize the Ti source in MXene to construct a heterojunction and uses the carbon framework remaining after MXene is converted into a three-dimensional structure as a conductive framework while also ensuring structural stability. Therefore, this invention does not need to consider avoiding MXene oxidation, because even if oxidation occurs, the required Ti source and carbon framework still exist. Thus, a major advantage of this invention is that it eliminates the need to consider avoiding MXene oxidation, thereby simplifying the process and streamlining the steps.
[0028] 4. This invention employs spray drying followed by high-temperature heat treatment. This allows for the control of the internal pore structure of the sulfonated polystyrene spheres during thermal decomposition, resulting in a simple preparation method with a short cycle and high yield. Furthermore, compared to the hydrothermal reaction in existing technologies, the spray drying method of this invention eliminates the need for high temperature and high pressure, significantly improving safety and facilitating mass production. Attached Figure Description
[0030] Figure 1 The XRD pattern of the TiN-Fe3N / C-2 heterojunction material prepared in Example 1 of this invention is shown below.
[0031] Figure 2 The image shows the Raman spectrum of the TiN-Fe3N / C-2 heterojunction material prepared in Example 1 of this invention.
[0032] Figure 3 The images shown are SEM images of the Fe-MXene and TiN-Fe3N / C-2 heterojunction materials prepared in Example 1 of this invention.
[0033] Figure 4 The rate performance of the heterojunction materials prepared in Example 1 and Comparative Example 1 in the specific embodiments of the present invention when applied to lithium-sulfur batteries. Detailed Implementation
[0035] This specific embodiment discloses a method for preparing three-dimensional porous MXene-derived heterojunction materials, with the following examples.
[0036] Example 1:
[0037] A method for preparing three-dimensional porous MXene-derived heterojunction materials includes the following steps:
[0038] S1: The Al layer was peeled off from Ti3AlC2 powder by acid etching, and then ultrasonicated at 18~24℃ for 4~6 h by mechanical peeling to obtain a few-layer or monolayer MXene dispersion with an MXene concentration of 3.0 mg / mL.
[0039] S2: Disperse 0.5 g of ferric nitrate hexahydrate in 100 mL of the MXene dispersion obtained in step S1 to obtain the first dispersion; disperse 0.5 g of sulfonated polystyrene spheres in 50 mL of anhydrous ethanol and ultrasonically disperse them evenly to obtain the second dispersion; the mass ratio of MXene to sulfonated polystyrene spheres is 1:1.66, and the mass ratio of MXene to ferric nitrate hexahydrate is 1:1.66.
[0040] S3: The second dispersion is slowly added to the first dispersion and stirred evenly. The resulting mixed solution is then introduced into a spray drying equipment and spray dried at an inlet temperature of 140 ℃ and a flow rate of 600 mL / h to obtain the precursor material.
[0041] S4: The precursor material obtained in step S3 is heated to 250 ℃ at a rate of 2 ℃ / min in an Ar atmosphere and held at this temperature for 1 h; then heated to 750 ℃ at a rate of 4 ℃ / min and held at this temperature for 2 h; then the precursor material is subjected to isothermal nitriding treatment in an NH3 atmosphere at 750 ℃ for 2 h, finally obtaining the TiN-Fe3N / C heterojunction material derived in situ from MXene, namely the three-dimensional porous MXene-derived heterojunction material, named TiN-Fe3N / C-2.
[0042] Comparative Example 1:
[0043] A method for preparing three-dimensional porous MXene-derived heterojunction materials includes the following steps:
[0044] S1: The Al layer was peeled off from Ti3AlC2 powder by acid etching, and then ultrasonicated at 18~24℃ for 4~6 h by mechanical peeling to obtain a few-layer or monolayer MXene dispersion with an MXene concentration of 3.0 mg / mL.
[0045] S2: Take 100 mL of the MXene dispersion obtained in step S1, without using ferric nitrate hexahydrate, to obtain the first dispersion; disperse 0.5 g of sulfonated polystyrene spheres in 50 mL of anhydrous ethanol, and ultrasonically disperse them evenly to obtain the second dispersion;
[0046] S3: The second dispersion is slowly added to the first dispersion and stirred evenly. The resulting mixed solution is then introduced into a spray drying equipment and spray dried at an inlet temperature of 140 ℃ and a flow rate of 600 mL / h to obtain the precursor material.
[0047] S4: The precursor material obtained in step S3 is heated to 250 ℃ at a rate of 2 ℃ / min in an Ar atmosphere and held at this temperature for 1 h; then heated to 750 ℃ at a rate of 4 ℃ / min and held at this temperature for 2 h; then the precursor material is subjected to isothermal nitriding treatment in an NH3 atmosphere at 750 ℃ for 2 h, finally obtaining the TiN-Fe3N / C heterojunction material derived in situ from MXene, namely the three-dimensional porous MXene-derived heterojunction material, named TiN-Fe3N / C-0.
[0048] The product obtained in this embodiment was subjected to X-ray diffraction analysis, and the results are shown below. Figure 1 The prepared heterojunction material TiN-Fe3N / C-2 has a high degree of crystallinity compared to the comparative example, has no impurity phase, and the characteristic peaks of XRD are consistent with the standard cards of TiN (JCPDS No. 38-1420) and Fe3N (JCPDS No. 73-2101).
[0049] Figure 2 The Raman spectroscopy of the product obtained in this embodiment is shown at 152 cm⁻¹. -1 Raman scattering peaks of TiN can be observed at 211, 280, and 387 cm⁻¹; simultaneously, peaks are observed at 211, 280, and 387 cm⁻¹. -1 Raman scattering peaks belonging to Fe3N can be observed at the location. The coexistence of scattering peaks of TiN and Fe3N further proves the successful synthesis of TiN-Fe3N / C-2 heterojunction materials, which can be corroborated by the XRD results.
[0050] Figure 3 Here is an SEM image of the product obtained in this embodiment. Figure 3 In image a, it can be clearly observed that the sample is composed of aggregated spheres coated with MXene, in which sulfonated polystyrene spheres act as templates to construct the hollow structure. Figure 3 b is a scan image of the heterojunction material TiN-Fe3N / C-2 finally prepared in Example 1. The broken part shows its hollow structure. When this heterojunction material is used in lithium-sulfur batteries, these hollow structures can alleviate the volume expansion of sulfur during charging and discharging, and ensure the stability of the positive electrode during cycling.
[0051] Application of Example 1 and Comparative Example 1:
[0052] The products obtained in Example 1 and Comparative Example 1 were mixed with sulfur powder and treated at 155 °C for 12 h to obtain composite materials. These composite materials were then ground and mixed evenly with carbon black and PVDF, stirred in NMP solution to obtain a slurry, coated on aluminum foil, dried at 60 °C for 12 h, and cut into electrode sheets with a diameter of 12 mm. These electrodes were used as the positive electrode of lithium-sulfur batteries and encapsulated into coin cells. The specific steps included the following: using lithium metal as the negative electrode, Celgard 2400 as the separator, and 1.0 M lithium bis(trifluoromethanesulfonyl)imide solution as the electrolyte, the battery was assembled in a CR2032 battery case.
[0053] The electrochemical performance of the obtained packaged coin cells was characterized, and the results are shown in the figure. Figure 4 The results showed that when the TiN-Fe3N / C-2 heterojunction material prepared in Example 1 was used as the cathode of a lithium-sulfur battery, the battery exhibited good rate performance. Figure 4 It is evident that the TiN-Fe3N / C-2 cathode outperforms the comparative TiN-Fe3N / C-0 cathode at different charge / discharge rates. At a discharge rate of 0.1 C, the TiN-Fe3N / C-2 cathode exhibits a discharge specific capacity as high as 1485 mAh / g, and even at a high current density of 5.0 C, its discharge specific capacity still reaches 785 mAh / g. After returning to a lower current density of 0.2 C from the high current density, its specific capacity still recovers to 1306 mAh / g.
[0054] Example 2:
[0055] A method for preparing three-dimensional porous MXene-derived heterojunction materials includes the following steps:
[0056] S1: The Al layer was peeled off from Ti3AlC2 powder by acid etching, and then ultrasonicated at 18~24℃ for 4~6 h by mechanical peeling to obtain a few-layer or monolayer MXene dispersion with an MXene concentration of 3.0 mg / mL.
[0057] S2: Disperse 0.25 g of ferric nitrate hexahydrate in 100 mL of the MXene dispersion obtained in step S1 to obtain the first dispersion; disperse 0.5 g of sulfonated polystyrene spheres in 50 mL of anhydrous ethanol and ultrasonically disperse them evenly to obtain the second dispersion; the mass ratio of MXene to sulfonated polystyrene spheres is 1:1.66, and the mass ratio of MXene to ferric nitrate hexahydrate is 1:0.83;
[0058] S3: The second dispersion is slowly added to the first dispersion and stirred evenly. The resulting mixed solution is then introduced into a spray drying equipment and spray dried at an inlet temperature of 140 ℃ and a flow rate of 600 mL / h to obtain the precursor material.
[0059] S4: The precursor material obtained in step S3 is heated to 250 ℃ at a rate of 2 ℃ / min in an Ar atmosphere and held at this temperature for 1 h; then heated to 750 ℃ at a rate of 4 ℃ / min and held at this temperature for 2 h; then the precursor material is subjected to isothermal nitriding treatment in an NH3 atmosphere at 750 ℃ for 2 h, finally obtaining the TiN-Fe3N / C heterojunction material derived in situ from MXene, namely the three-dimensional porous MXene-derived heterojunction material, named TiN-Fe3N / C-1.
[0060] Example 3:
[0061] A method for preparing three-dimensional porous MXene-derived heterojunction materials includes the following steps:
[0062] S1: The Al layer was peeled off from Ti3AlC2 powder by acid etching, and then ultrasonicated at 18~24℃ for 4~6 h by mechanical peeling to obtain a few-layer or monolayer MXene dispersion with an MXene concentration of 3.0 mg / mL.
[0063] S2: Disperse 0.75 g of ferric nitrate hexahydrate in 100 mL of the MXene dispersion obtained in step S1 to obtain the first dispersion; disperse 0.5 g of sulfonated polystyrene spheres in 50 mL of anhydrous ethanol and ultrasonically disperse them evenly to obtain the second dispersion; the mass ratio of MXene to sulfonated polystyrene spheres is 1:1.66, and the mass ratio of MXene to ferric nitrate hexahydrate is 1:2.5;
[0064] S3: The second dispersion is slowly added to the first dispersion and stirred evenly. The resulting mixed solution is then introduced into a spray drying equipment and spray dried at an inlet temperature of 140 ℃ and a flow rate of 600 mL / h to obtain the precursor material.
[0065] S4: The precursor material obtained in step S3 is heated to 250 ℃ at a rate of 2 ℃ / min in an Ar atmosphere and held at this temperature for 1 h; then heated to 750 ℃ at a rate of 4 ℃ / min and held at this temperature for 2 h; then the precursor material is subjected to isothermal nitriding treatment in an NH3 atmosphere at 750 ℃ for 2 h, finally obtaining the TiN-Fe3N / C heterojunction material derived in situ from MXene, namely the three-dimensional porous MXene-derived heterojunction material, named TiN-Fe3N / C-3.
[0066] This specific embodiment also discloses a three-dimensional porous MXene-derived heterojunction material prepared by the aforementioned method, and a sulfur-three-dimensional porous MXene-derived heterojunction composite material. The sulfur-three-dimensional porous MXene-derived heterojunction composite material is composed of a three-dimensional porous MXene-derived heterojunction material and sulfur.
[0067] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.
Claims
1. A method of preparing a three-dimensional porous MXene-derived heterojunction material, characterized by: The method comprises the following steps: S1: Al layer is peeled off from Ti3AlC2 powder by etching method, and then a few-layer or single-layer MXene dispersion liquid is obtained by mechanical exfoliation method; S2: iron nitrate hexahydrate is dispersed in the MXene dispersion liquid obtained in step S1 to obtain a first dispersion liquid; sulfonated polystyrene balls are dispersed in anhydrous ethanol, and ultrasonic dispersion is performed to obtain a second dispersion liquid; S3: the second dispersion liquid is slowly added into the first dispersion liquid, and after uniform stirring, the obtained mixed solution is introduced into a spray drying device, and a precursor material is obtained after drying; S4: the precursor material obtained in step S3 is heat-treated in an inert atmosphere, and then heat-treated in ammonia, and finally a three-dimensional porous MXene derived heterojunction material is obtained.
2. The method of claim 1, wherein: The mechanical exfoliation method in step S1 is ultrasonic treatment for 4-6 h at a temperature of 18-24℃.
3. The method of claim 1, wherein: In step S2, the concentration of sulfonated polystyrene balls in the second dispersion liquid is 1.25 wt%.
4. The method of claim 1, wherein: In step S1, the concentration of MXene is 3-5 mg / mL; the mass ratio of MXene to sulfonated polystyrene balls is 1:1.6-1:1.8; and the mass ratio of MXene to iron nitrate hexahydrate is 1:0.8-1:2.
6.
5. The method of claim 1, wherein: In step S4, the temperature for heat treatment in an inert atmosphere is 200-800℃, and the heat treatment time is 1-4 h; the temperature for heat treatment in ammonia is 200-800℃, and the heat treatment time is 1-4 h.
6. The method of claim 1, wherein: In step S4, the heat treatment in an inert atmosphere is first heat treatment at 200-300℃ for 1-2 h, and then heat treatment at 600-800℃ for 2-4 h.
7. The method of claim 1, wherein: In step S4, the heat treatment in an inert atmosphere is first heat treatment at 250℃ for 1-2 h, and then heat treatment at 750℃ for 2-4 h.
8. The method of claim 1, wherein: In step S4, the heat treatment in ammonia is heat treatment at 750℃ for 2 h.
9. A three-dimensional porous MXene derived heterojunction material prepared by the method of any one of claims 1-8.
10. A sulfur-three-dimensional porous MXene-derived heterojunction composite material, characterized in that: The three-dimensional porous MXene derived heterojunction material of claim 9 is compounded with sulfur.