Preparation method of MnF2 / MXene composite material and application of MnF2 / MXene composite material in lithium ion battery
By growing MnF2 nanoparticles on the surface and between layers of MXene, a MnF2/MXene composite material is formed, which solves the problems of low coulombic efficiency and poor cycle stability of MXene anode materials and achieves high energy density and excellent charge transport performance.
Patent Information
- Application Number
- CN202511659414.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-13
- Publication Date
- 2026-02-17
AI Technical Summary
Existing lithium-ion battery anode material MXene suffers from low initial coulombic efficiency and poor cycle stability due to its surface functional groups and high defect content, making it difficult to meet the requirements for high energy density and high power density.
MnF2 nanoparticles were grown on the surface and between layers of MXene by acid etching and high-temperature solvothermal method, and then connected by Ti-F-Mn bonds to form a MnF2/MXene composite material.
By combining the high conductivity of MXene with the lithium conversion and storage mechanism of MnF2, the energy density and charge transport performance are improved, the cycle stability is enhanced, and the volume expansion effect is suppressed.
Smart Images
Figure CN121546017A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of lithium ion batteries, and particularly relates to a preparation method of a MnF2 / MXene composite material and application thereof in lithium ion batteries. BACKGROUND
[0002] Electrochemical energy storage technology is the core guarantee for building a new energy system. The development of lithium ion batteries supports three core time lengths of consumer electronics, power batteries and energy storage batteries. However, the performance of lithium ion batteries with graphite-based materials as the negative electrode has reached the limit, and it is difficult to meet the requirements of high energy density and high power density due to the slow embedding / extraction lithium storage mechanism.
[0003] As a new type of two-dimensional material, two-dimensional transition metal carbide (MXene) has metal-like conductivity, rich and adjustable surface functional groups, and other properties, making it widely studied in the fields of secondary batteries, electromagnetic shielding, photo-thermal conversion, water treatment and hydrogen storage. In particular, the large interlayer spacing of MXene can accommodate alkali metal ions such as Li + , Na + , K + , etc., making it a promising negative electrode material for alkali metal ion batteries. However, a large number of studies have shown that although MXene can exhibit high initial discharge specific capacity as a negative electrode for lithium ion batteries, the low initial coulombic efficiency and poor cycle stability due to surface functional groups and rich defects greatly limit its application in lithium ion batteries. SUMMARY
[0004] The purpose of this section is to summarize some aspects of the embodiments of the application and briefly introduce some preferred embodiments.
[0005] As one aspect of the application, a preparation method of a MnF2 / MXene composite material is provided, wherein MnF2nanoparticles are grown on the surface and interlayer of MXene through acid etching and high-temperature solvothermal method, and MnF2is connected with MXene through Ti-F-Mn bond.
[0006] As a preferred scheme of the preparation method of the MnF2 / MXene composite material, the method comprises the following steps:
[0007] (1) Preparation of MXene: slowly add MAX phase material Ti3AlC2to a hydrofluoric acid solution, continuously stir, and then obtain MXene powder after centrifugation, washing and freeze-drying; the mass concentration of the hydrofluoric acid solution is 38-48%;
[0008] (2) Preparation of MnF2 / MXene composite material: MXene powder is added into ethylene glycol / water mixed solvent, and ultrasonic dispersion is carried out under inert gas protection; manganese acetate, ascorbic acid and polyvinylpyrrolidone are added, and high-temperature solvothermal reaction is carried out after sufficient stirring, and then the MnF2 / MXene composite material is obtained after natural cooling, centrifugation, washing and freeze-drying.
[0009] As a preferred scheme of the preparation method of the MnF2 / MXene composite material, in step (1), the mass-volume ratio of Ti3AlC2 to hydrofluoric acid solution is 1-4 g:10 mL, and the etching time is 12-24 h.
[0010] As a preferred scheme of the preparation method of the MnF2 / MXene composite material, in step (2), the volume ratio of ethylene glycol to water in the ethylene glycol / water mixed solvent is 2-3:1.
[0011] As a preferred scheme of the preparation method of the MnF2 / MXene composite material, in step (2), the mass-volume ratio of MXene powder to ethylene glycol / water mixed solvent is 5-20 mg:1 mL.
[0012] As a preferred scheme of the preparation method of the MnF2 / MXene composite material, in step (2), the mass-volume ratio of manganese acetate, ascorbic acid, polyvinylpyrrolidone to ethylene glycol / water mixed solvent is 5-20 mg:0.5-1 mg:1-2 mg:1 mL.
[0013] As a preferred scheme of the preparation method of the MnF2 / MXene composite material, in step (2), the solvothermal reaction temperature is 120-180℃, and the holding time is 12-24 h.
[0014] As a preferred scheme of the preparation method of the MnF2 / MXene composite material, in step (2), the inert gas includes argon; and the polyvinylpyrrolidone includes PVP-K30.
[0015] The application also provides the application of the MnF2 / MXene composite material prepared by the preparation method in lithium ion batteries: the MnF2 / MXene composite material is used as a negative electrode of a lithium ion battery.
[0016] The beneficial effects of this invention are as follows: The preparation method provided by this invention uses a simple acid etching combined with a high-temperature solvothermal method to prepare MXene-supported MnF2 or MnO composite materials. This method utilizes the fluorine / oxygen-rich and defect-rich environment on the surface of MXene sheets to induce the deposition and nucleation of MnF2 or MnO. The resulting MnF2 / MXene composite material combines the advantages of MXene's high conductivity and rapid pseudocapacitive lithium storage mechanism with the high energy density brought by Mn(II) conversion lithium storage mechanism, exhibiting both high energy density and excellent charge transport performance. Furthermore, the transformation of functional groups and defects on the MXene surface effectively improves the capacity decay problem. In addition, the excellent mechanical properties of MXene can effectively suppress the volume expansion effect during the Mn(II) lithium storage process, improving the cycling stability of the electrode. Attached Figure Description
[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below, wherein:
[0018] Figure 1 Here is a scanning electron microscope image of the sample from Example 1;
[0019] Figure 2 This is a mapping diagram of the sample from Example 1;
[0020] Figure 3 The X-ray diffraction pattern of the sample from Example 1;
[0021] Figure 4 The electron paramagnetic resonance spectrum of the sample from Example 1;
[0022] Figure 5 The image shows the Mn 3s X-ray photoelectron spectrum of the sample from Example 1.
[0023] Figure 6 The F 1s X-ray photoelectron spectrum of the sample from Example 1;
[0024] Figure 7 Mapping diagram of sample from Example 2
[0025] Figure 8 The X-ray diffraction pattern of the sample in Example 2;
[0026] Figure 9 The X-ray diffraction pattern of the sample in Example 3;
[0027] Figure 10 Here is a scanning electron microscope image of the sample from Example 4;
[0028] Figure 11 Scanning electron microscope image of sample from Example 5
[0029] Figure 12 The first three cycles of constant current charge / discharge are shown for the sample of Example 1 as the negative electrode.
[0030] Figure 13 The first three cycles of constant current charge / discharge are shown for the sample of Example 2 as the negative electrode;
[0031] Figure 14 The first three cycles of constant current charge / discharge are shown for the sample of Example 3 as the negative electrode;
[0032] Figure 15 The first three cycles of constant current charge / discharge are shown for the sample of Example 4 as the negative electrode.
[0033] Figure 16 The first three cycles of constant current charge / discharge are shown for the sample of Example 5 as the negative electrode;
[0034] Figure 17 The graph shows a comparison of the cycle performance of samples 1-5 as negative electrodes.
[0035] Figure 18 The cycling performance of the sample in Comparative Example 1 as the negative electrode is shown in the graph.
[0036] Figure 19 The cycling performance of the sample in Comparative Example 2 as the negative electrode is shown in the graph.
[0037] Figure 20 The graph shows the cycling performance of the sample used as the negative electrode in Comparative Example 3. Detailed Implementation
[0038] To make the above-mentioned objectives, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to specific examples.
[0039] Example 1:
[0040] This embodiment provides a method for preparing a MnF2 / MXene composite material, including the following steps:
[0041] (1) Preparation of MXene-48 material: 2g of Ti3AlC2 MAX phase was added to 20mL of 48% hydrofluoric acid aqueous solution and stirred continuously at room temperature (25℃) for 24h. Then, it was centrifuged and washed with deionized water until the pH was about 6. Finally, MXene-48 powder was obtained after freeze drying.
[0042] (2) Preparation of MnF2 / MXene composite material: 14 mL of ethylene glycol and 6 mL of deionized water were mixed and stirred to obtain ethylene glycol / water mixed solvent. 100 mg of MXene-48 powder was added and dispersed by ultrasonication (power 480 W) for 30 min under argon protection. Subsequently, 0.2 g of anhydrous manganese acetate, 0.01 g of L-ascorbic acid and 0.02 g of PVP-K30 were added in sequence. After thorough stirring, the mixture was transferred to a polytetrafluoroethylene liner and placed in a matching stainless steel reactor. The mixture was reacted in a forced-air oven at 180 °C for 12 h. After natural cooling, the product was centrifuged, washed with ethanol / deionized water, and freeze-dried at -50 °C for 72 h to obtain MnF2 / MXene composite material powder.
[0043] Figure 1 The image shows a scanning electron microscope image of the MnF2 / MXene composite material prepared in Example 1. As can be seen from the image, the composite material still retains the accordion-like microstructure of MXene. MnF2 nanoparticles grow on the surface and between the layers of MXene and are evenly distributed. Figure 2 The image shows the mapping diagram of the sample from Example 1, in which Ti and C elements from Ti3C2 are uniformly distributed throughout the entire sheet; while Mn and F elements are mainly distributed on the nanoparticles on the surface, indicating that the nanoparticles are manganese fluorides. Figure 3 The X-ray diffraction pattern of the sample in Example 1 shows that the composite material retains the MXene phase, and the presence of the MnF2 phase indicates successful synthesis. Furthermore, the growth of MnF2 nanoparticles within the MXene interlayer causes the 002 crystal plane peak to shift to a lower angle, indicating an increased interlayer spacing that can accommodate more electrolyte ions. Figure 4 The image shows the electron paramagnetic resonance spectrum of the MnF2 / MXene composite material prepared in Example 1. The signal in the image originates from Mn. 2+ This proves the existence of MnF2. Figure 5 The X-ray photoelectron spectrum of Mn 3s from the sample of Example 1 shows an energy difference of 6.09 eV between the two split peaks, indicating that the average oxidation state of Mn is +2.1; simultaneously, Figure 6 The F 1s spectrum confirmed the existence of the Mn-F bond, indicating that MnF2 and MXene are connected by Ti-F-Mn bonds, and the strong chemical bonding ensures the stability of the MnF2 / MXene composite material.
[0044] Example 2:
[0045] This embodiment provides a method for preparing a MnO / MXene composite material, including the following steps:
[0046] (1) Preparation of MXene-20 material: The process is the same as step (1) in Example 1, except that the hydrofluoric acid solution is diluted with deionized water to a mass fraction of 20% to obtain MXene-20 powder.
[0047] (2) Preparation of MnO / MXene composite material: The process is the same as step (2) in Example 1, except that MXene-48 is replaced with MXene-20.
[0048] Figure 7 The images show scanning electron microscopy (SEM) and mapping of the sample from Example 2. Compared to the sample from Example 1, its morphology has changed significantly; the mapping shows that the surface particles are mainly composed of Mn and O elements. This is because the MXene-20 surface obtained by etching with a low-concentration hydrofluoric acid solution contains only a small amount of F functional groups, while O-containing functional groups are dominant, thus the resulting compounds are mainly manganese oxides. Further... Figure 8 The X-ray diffraction pattern revealed that the compound was MnO.
[0049] Example 3:
[0050] This embodiment provides a method for preparing a MnO / MnF2 / MXene composite material, which includes the following steps: the preparation process is the same as in Example 1, except that the amount of manganese acetate, ascorbic acid, and PVP-K30 added in step (2) is increased to 0.4g, 0.02g, and 0.04g, respectively.
[0051] Figure 9 The X-ray diffraction pattern of the sample in Example 3 shows the simultaneous presence of MnF2 and MnO; indicating that after the excess manganese acetate reacts with the F functional group on the MXene-48 surface, it continues to react with the O functional group to generate MnO.
[0052] Example 4:
[0053] This embodiment provides an MXene-48 material, prepared using the same method as step (1) in Embodiment 1.
[0054] Figure 10 The image shows a scanning electron microscope image of the MXene-48 material prepared in Example 4. As can be seen from the image, the MXene material has a typical accordion-like morphology, good uniformity, and smooth lamellar surface.
[0055] Example 5:
[0056] This embodiment provides an MXene-20 material, prepared using the same method as step (1) in Embodiment 2.
[0057] Figure 11The image shows a scanning electron microscope (SEM) image of the MXene-20 material prepared in Example 5. The sample exhibits a typical accordion-like morphology. However, due to the lower etching concentration, the sheet thickness is slightly greater than that of the sample in Example 4.
[0058] Example 6:
[0059] The electrochemical performance of the materials in Examples 1-5 was tested, and the specific process is as follows:
[0060] (1) Electrode preparation: The powder samples of Examples 1 to 5 were mixed with polyvinylidene fluoride and acetylene black in a mass ratio of 8:1:1 and ground thoroughly. Then, an appropriate amount of N-methylpyrrolidone was added and ground to obtain a uniform slurry. The slurry was coated onto a copper foil current collector, dried under vacuum at 80°C, and then stamped into a circular electrode sheet.
[0061] (2) Battery assembly: In a glove box with a high-purity argon atmosphere, the CR2032 negative electrode shell, circular lithium metal sheet, Celgard-2325 separator, electrolyte (1 mol / L lithium hexafluorophosphate dissolved in dimethyl carbonate, ethylene carbonate and ethyl methyl carbonate in a volume ratio of 1:1:1, with 2% fluoroethylene carbonate added in a volume ratio), electrode sheet, stainless steel gasket, stainless steel spring sheet and CR2032 positive electrode shell are stacked in sequence and pressurized to obtain a coin cell.
[0062] Figures 12-16 The first three discharge curves of the samples from Examples 1-5 used as the negative electrode of a lithium-ion battery are shown. Figure 12 The initial discharge plateau of 0.28V in the middle stage is the reduction of MnF2 to Mn. 0 The reaction; in subsequent cycles, due to kinetic optimization, the discharge plateau shifts to 0.52V. Figure 13 The discharge plateau between 0.6 and 0.75 ppm originates from the reduction of MnO to Mn. 0 The reaction. Similarly, Figure 14 The discharge plateau in the figure corresponds to the reduction of MnF2 / MnO to Mn. 0 process. Figure 15 and 16 The irreversible discharge plateau of around 0.5V in the first cycle indicates severe side reactions caused by the fluorine-rich environment on the surface. Figure 17 The figures show a comparison of cycling performance for the five sample examples. As can be seen from the figures, MXene-48 and MXene-20 exhibit poor cycling performance due to their surface-active functional groups, with reversible capacities of 115 and 174 mAh / g after 100 cycles, respectively. However, depending on the surface chemistry of different MXenes, electrodes loaded with MnO or MnF2 in situ using a simple hydrothermal method showed enhanced specific capacity and cycling stability. The reversible specific capacities of Examples 1-3 after 100 cycles were 360, 303, and 347 mAh / g, respectively.
[0063] Comparative Example 1:
[0064] The preparation of a Mn-MXene-1 material includes the following steps:
[0065] The preparation process is the same as in Example 1, except that after adding PVP-K30 in step (2), an additional 0.2g of ammonium fluoride is added.
[0066] Figure 18 The graph shows the cycling performance of the sample from Comparative Example 1 as the negative electrode of a lithium-ion battery. The discharge specific capacities after the first and 100 cycles are 238 and 165 mAh / g, respectively. The Mn content in the system... 2+ It preferentially reacts with free fluoride ions, resulting in MnF2 with poor binding force to MXene; at the same time, the intrinsic conductivity of MnF2 is low, which further affects the electrochemical performance of the material.
[0067] Comparative Example 2:
[0068] This embodiment provides a method for preparing Mn-MXene-2 material, including the following steps:
[0069] The preparation process is the same as in Example 1, but instead of a hydrothermal reaction, it is kept in an oil bath at 80°C for 12 hours.
[0070] Figure 19 The graph shows the cycling performance of the Comparative Example 2 sample as the negative electrode of a lithium-ion battery. The initial and 100-cycle discharge specific capacities were 460 and 122 mAh / g, respectively, slightly better than the MXene-48 sample of Example 4. The 80°C atmospheric pressure reaction conditions in the oil bath made it difficult to activate the Ti-F bond, and the Mn... 2+ The reactivity with surface fluorine functional groups is low, resulting in less MnF2 production and no significant improvement in electrochemical performance.
[0071] Comparative Example 3:
[0072] This comparative example provides a method for preparing a LiF / MXene material, including the following steps:
[0073] 0.1 mL of acetic acid, 10 mL of deionized water, and 10 mL of anhydrous ethanol were thoroughly mixed, and 0.2 g of lithium acetate was added and stirred until dissolved. 100 mg of MXene-48 was added to the solution. The mixture was stirred at 80 °C for 24 h under argon protection. Finally, the mixture was washed with anhydrous ethanol / deionized water and vacuum dried at 80 °C to obtain the LiF / MXene material.
[0074] Figure 20The graph shows the cycling performance of Comparative Example 3 as the negative electrode of a lithium-ion battery. The initial discharge specific capacity and the discharge capacity after 100 cycles are 353 and 160 mAh / g, respectively, with an initial coulombic efficiency of 58%. An acidic environment can activate the Ti-F bond, and Li... + After capture, LiF can be generated in situ. As the main inorganic component of SEI, the generated LiF can effectively improve the first coulombic efficiency of the material and reduce the capacity decay rate. However, LiF has no lithium storage sites and therefore does not improve the relative capacity.
[0075] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.
Claims
1. A method for preparing a MnF2 / MXene composite material, characterized in that: MnF2 nanoparticles were grown on the surface and between layers of MXene using acid etching and high-temperature solvothermal methods, and MnF2 was connected to MXene through Ti-F-Mn bonds.
2. The method for preparing the MnF2 / MXene composite material according to claim 1, characterized in that: Includes the following steps, (1) Preparation of MXene: MAX phase material Ti3AlC2 was slowly added to hydrofluoric acid solution and stirred continuously. Then, after centrifugation, washing, and freeze-drying, MXene powder was obtained; the mass concentration of the hydrofluoric acid solution was 38-48%. (2) Preparation of MnF2 / MXene composite material: MXene powder was added to ethylene glycol / water mixed solvent and ultrasonically dispersed under inert gas protection; manganese acetate, ascorbic acid and polyvinylpyrrolidone were added, and after thorough stirring, a high-temperature solvothermal reaction was carried out. After natural cooling, the MnF2 / MXene composite material was obtained by centrifugation, washing and freeze drying.
3. The method for preparing the MnF2 / MXene composite material according to claim 2, characterized in that: In step (1), the mass-to-volume ratio of Ti3AlC2 to hydrofluoric acid solution is 1-4 g: 10 mL, and the etching time is 12-24 h.
4. The method for preparing the MnF2 / MXene composite material according to claim 2 or 3, characterized in that: In step (2), the volume ratio of ethylene glycol to water in the ethylene glycol / water mixed solvent is 2-3:
1.
5. The method for preparing the MnF2 / MXene composite material according to claim 2 or 3, characterized in that: In step (2), the mass-to-volume ratio of MXene powder to ethylene glycol / water mixed solvent is 5~20 mg:1 mL.
6. The method for preparing the MnF2 / MXene composite material according to claim 2 or 3, characterized in that: In step (2), the mass-volume ratios of manganese acetate, ascorbic acid, polyvinylpyrrolidone and ethylene glycol / water mixed solvent are 5-20 mg: 0.5-1 mg: 1-2 mg: 1 mL.
7. The method for preparing the MnF2 / MXene composite material according to claim 2 or 3, characterized in that: In step (2), the solvothermal reaction temperature is 120-180℃ and the holding time is 12-24h.
8. The method for preparing the MnF2 / MXene composite material according to claim 2 or 3, characterized in that: In step (2), the inert gas includes argon; the polyvinylpyrrolidone includes PVP-K30.
9. The application of the MnF2 / MXene composite material prepared by the method according to claim 1 in lithium-ion batteries, characterized in that: The MnF2 / MXene composite material is used as the negative electrode of a lithium-ion battery.