MXene-based negative electrode material and preparation method and application thereof

Abstract

The application discloses a kind of MXene-based negative electrode materials and preparation method and application thereof, belong to battery technical field.The MXene-based negative electrode material provided by the application is obtained by grafting modification of benzaldehyde and aminated MXene.The application utilizes the potential active site on the surface of aminated MXene, grafts it with benzaldehyde, gives the material greater interlayer spacing while not destroying the special layered structure, significantly improves the structural stability and oxidation resistance of the material, and accelerates the transmission kinetics of sodium ions, improves the rate performance and long cycle stability of the material as a negative electrode material, and greatly improves the long-term fast charge-discharge capability.The application utilizes the synergistic effect of the two modification strategies of "amination" and "benzaldehyde grafting", so that the electrochemical performance of the MXene-based negative electrode material is significantly improved, and then an excellent performance negative electrode and sodium ion battery can be obtained.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, and particularly relates to an MXene-based anode material, its preparation method, and its application. Background Technology

[0002] The rapidly growing demand for sustainable energy has spurred the development of high-performance energy storage devices. Among various energy storage devices, sodium-ion batteries (SIBs) have become an important solution due to their abundant resources and low cost. However, during charge and discharge, the insertion / extraction of sodium ions in the electrode material induces severe volumetric strain, leading to a significant decrease in the structural stability of the electrode material. Furthermore, the relatively slow diffusion kinetics of sodium ions limit their transport rate within the electrode material, thus affecting the battery's charge and discharge efficiency. These problems severely limit the cycle stability and energy density of sodium-ion batteries, making their performance unsuitable for practical applications. Therefore, developing anode materials that combine rapid ion diffusion kinetics with a stable structure has become crucial for the fabrication of high-performance sodium-ion batteries.

[0003] MXene materials have attracted widespread attention in recent years due to their excellent plasticity and unique layered structure. However, during repeated sodium ion insertion and extraction, MXene materials are prone to interlayer aggregation and stacking, which leads to a significant reduction in effective charge transport paths, resulting in key problems such as rate performance degradation and decreased cycle stability. Summary of the Invention

[0004] In order to overcome at least one of the problems existing in the prior art, one of the objectives of the present invention is to provide an MXene-based anode material with excellent electrochemical performance, and as an anode material, it has good rate performance, long cycle stability and long-term fast charge and discharge capability.

[0005] The second objective of this invention is to provide a method for preparing the above-mentioned MXene-based anode material.

[0006] The third objective of this invention is to provide a negative electrode.

[0007] The fourth objective of this invention is to provide a sodium-ion battery.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A first aspect of the present invention provides an MXene-based anode material, which is obtained by grafting benzaldehyde with amino-modified MXene.

[0009] This invention addresses the problem of interlayer aggregation and stacking in MXene materials by proposing an organic bridging engineering strategy to simultaneously optimize the volumetric strain characteristics and cycle stability of MXene-based anode materials. First, aminated MXene with a surface rich in potential active sites was successfully constructed through amination treatment, optimizing its electronic structure, improving its conductivity, and accelerating sodium ion transport kinetics, thereby enhancing the material's electrochemical performance. Further, benzaldehyde was grafted onto the aminated MXene, introducing "branching" that, without disrupting the unique layered structure, imparts a larger interlayer spacing, significantly improving the material's structural stability and oxidation resistance. This mitigates the stacking and structural collapse of MXene during battery cycling, increasing the material's cycle life. The resulting material is a composite material (Ti3C2-BD) with layered structural support, which significantly promotes charge transport behavior. The synergistic effect of the "amination" and "benzaldehyde grafting" modification strategies in this invention significantly improves the electrochemical performance of MXene-based anode materials.

[0010] In some embodiments of the present invention, the mass ratio of the amino-modified MXene to the benzaldehyde is 1:(1~10); for example, it can be any value or a range between 1:1, 1:2, 1:4, 1:6, 1:8 or 1:10; in some specific embodiments of the present invention, the mass ratio of the amino-modified MXene to the benzaldehyde is 1:(4~6).

[0011] In some embodiments of the present invention, the aminated MXene is prepared by a method comprising the following steps: mixing MXene, a surface modifier and water, and reacting to obtain the aminated MXene; the surface modifier comprises ammonium salt, ammonia water or a combination thereof.

[0012] In some embodiments of the present invention, in the method for preparing aminated MXene, the ratio of MXene to water is (0.03~0.3) g:100 mL; for example, it can be any value or a range between any two of 0.03 g:100 mL, 0.05 g:100 mL, 0.08 g:100 mL, 0.1 g:100 mL, 0.15 g:100 mL, 0.2 g:100 mL, 0.25 g:100 mL, or 0.3 g:100 mL; in some specific embodiments of the present invention, in the method for preparing aminated MXene, the ratio of MXene to water is (0.08~0.15) g:100 mL.

[0013] In some embodiments of the present invention, the mass ratio of MXene to the surface modifier is 1:(1~3); for example, it can be any value of 1:1, 1:1.5, 1:2, 1:2.5 or 1:3 or any range between two; in some specific embodiments of the present invention, the mass ratio of MXene to the surface modifier is 1:(1.5~2.5).

[0014] In some embodiments of the present invention, the surface modifier is selected from ammonium salts.

[0015] In some embodiments of the present invention, the ammonium salt is selected from ammonium fluoride.

[0016] In some embodiments of the present invention, the MXene is obtained by etching Ti3AlC2 with a fluorine-containing reagent.

[0017] In some embodiments of the present invention, the fluorine-containing reagent is selected from hydrofluoric acid (HF); in some embodiments of the present invention, the concentration of the hydrofluoric acid is 35~45wt%.

[0018] In some embodiments of the present invention, the etching time is 20-30 hours.

[0019] In some embodiments of the present invention, the etching temperature is 20~30°C.

[0020] In some embodiments of the present invention, the Ti3AlC2 accounts for 3 to 7 wt% of the fluorine-containing reagent.

[0021] In some embodiments of the present invention, the MXene-based anode material is a layered material with a layer spacing of 1 to 1.3 nm; for example, it can be any value or a range between 1 nm, 1.01 nm, 1.05 nm, 1.1 nm, 1.15 nm, 1.21 nm, 1.25 nm or 1.3 nm; in some specific embodiments of the present invention, the layer spacing of the MXene-based anode material is 1.01 to 1.21 nm.

[0022] A second aspect of the present invention provides a method for preparing an MXene-based anode material as described in the first aspect of the present invention, comprising the following steps: mixing benzaldehyde, amino-modified MXene and water, and performing a Schiff base reaction to obtain the MXene-based anode material.

[0023] In some embodiments of the present invention, in the preparation method of the MXene-based anode material, the ratio of the aminated MXene to water is (0.2~1.2) g:100 mL; for example, it can be any value or a range between 0.2 g:100 mL, 0.5 g:100 mL, 0.7 g:100 mL, 0.9 g:100 mL, 1 g:100 mL or 1.2 g:100 mL; in some specific embodiments of the present invention, in the preparation method of the MXene-based anode material, the ratio of the aminated MXene to water is (0.7~0.9) g:100 mL.

[0024] In some embodiments of the present invention, the mass of the aminoated MXene and the benzaldehyde is as described in the first aspect of the present invention.

[0025] In some embodiments of the present invention, the Schiff base reaction is carried out at a temperature of 20-30°C.

[0026] A third aspect of the present invention provides a negative electrode comprising a negative electrode current collector and a negative electrode active layer stacked thereon; the negative electrode active layer comprising the MXene-based negative electrode material described in the first aspect of the present invention.

[0027] In some embodiments of the present invention, the negative electrode active layer further includes a conductive agent and a binder.

[0028] In some embodiments of the present invention, the conductive agent is selected from Super-P.

[0029] In some embodiments of the present invention, the adhesive is selected from polyvinylidene fluoride (PVDF).

[0030] In some embodiments of the present invention, the mass ratio of the MXene-based anode material to the conductive agent is 1:(0.1~0.2).

[0031] In some embodiments of the present invention, the mass ratio of the MXene-based anode material to the binder is 1:(0.1~0.2).

[0032] In some embodiments of the present invention, the negative electrode is prepared by a method comprising the following steps: mixing MXene-based negative electrode material, conductive agent, binder and organic solvent to obtain a negative electrode slurry; applying the negative electrode slurry onto a negative electrode current collector and drying it to obtain the negative electrode.

[0033] In some embodiments of the present invention, the organic solvent is selected from N-methylpyrrolidone (NMP).

[0034] In some embodiments of the present invention, the negative current collector is selected from copper foil.

[0035] A fourth aspect of the present invention provides a sodium-ion battery comprising a positive electrode, a negative electrode, and an electrolyte; wherein the negative electrode comprises the MXene-based negative electrode material described in the first aspect of the present invention.

[0036] In some embodiments of the present invention, the electrolyte may be an electrolyte solution or a solid electrolyte.

[0037] In some embodiments of the present invention, the electrolyte is an electrolyte solution, and the sodium-ion battery further includes a separator.

[0038] In some embodiments of the present invention, the diaphragm is selected from glass fiber diaphragms.

[0039] In some embodiments of the present invention, the positive electrode is metallic sodium.

[0040] The beneficial effects of this invention are: This invention utilizes the potential active sites on the surface of aminated MXene, grafting them with benzaldehyde. This process imparts a larger interlayer spacing to the material without disrupting its unique layered structure, significantly improving its structural stability and oxidation resistance, accelerating sodium ion transport kinetics, and enhancing its rate performance and long-cycle stability as an anode material. This greatly improves its long-term rapid charge-discharge capability. This invention leverages the synergistic effect of two modification strategies—amination and benzaldehyde grafting—to significantly improve the electrochemical performance of MXene-based anode materials, thereby enabling the production of high-performance anodes and sodium-ion batteries. Attached Figure Description

[0041] Figure 1 The specific capacity-cycle count diagrams are for batteries made from the materials of Examples 1-3 and Comparative Example 1.

[0042] Figure 2 The first charge-discharge curves of the batteries made from the materials of Examples 1-3 and Comparative Example 1 are shown.

[0043] Figure 3 Impedance diagrams of batteries made from the materials of Examples 1-3 and Comparative Example 1 after 200 cycles.

[0044] Figure 4 The specific capacity-cycle count diagrams are for batteries made from the materials of Example 1 and Comparative Examples 2-3. Detailed Implementation

[0045] The following specific embodiments further illustrate the content of the present invention in detail. It should also be understood that the following embodiments are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Non-essential improvements and adjustments made by those skilled in the art based on the principles described herein are all within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make selections within a suitable range based on the description herein, and are not intended to be limited to the specific data in the examples below. Unless otherwise specified, the raw materials, reagents, or apparatus used in the following embodiments and comparative examples can be obtained from conventional commercial sources or by existing known methods.

[0046] It should be noted that the room temperature below refers to 25±5℃.

[0047] Preparation Example 1 An amination-modified MXene is obtained by etching and amination modification of Ti3AlC2. The specific preparation steps are as follows: (1) First, 3g of Ti3AlC2 powder was slowly added to a plastic beaker containing 60mL of 40wt% HF solution using a plastic spatula, and the mixture was magnetically stirred at room temperature for 24h. Then, the resulting solution was centrifuged multiple times at 3000rpm until the pH of the suspension was >6. Next, the obtained solid was added to deionized water and sonicated for 20min, then washed and filtered with deionized water. Finally, the filtered solid was dried at 60℃ for 12h, ground to obtain MXene powder, and stored in a sealed container.

[0048] (2) Disperse 0.1g of the above MXene powder in 100mL of deionized water by ultrasonication to obtain MXene dispersion; add 0.2g of ammonium fluoride to 100mL of MXene dispersion, stir and mix thoroughly, and obtain aminated MXene powder after solid-liquid separation.

[0049] Example 1 A benzaldehyde-grafted MXene-based anode material is prepared using the following steps: 0.8 g of the aminoated MXene prepared in Preparation Example 1 was ultrasonically dispersed in 100 mL of deionized water to obtain an aminoated MXene dispersion; 4 g of benzaldehyde was added to the aminoated MXene dispersion and stirred thoroughly at room temperature to obtain a benzaldehyde-grafted MXene-based anode material.

[0050] Example 2 A benzaldehyde-grafted MXene-based anode material is prepared using the following steps: 0.8 g of the aminoated MXene prepared in Preparation Example 1 was ultrasonically dispersed in 100 mL of deionized water to obtain an aminoated MXene dispersion; 2 g of benzaldehyde was added to the aminoated MXene dispersion and stirred thoroughly at room temperature to obtain a benzaldehyde-grafted MXene-based anode material.

[0051] Example 3 A benzaldehyde-grafted MXene-based anode material is prepared using the following steps: 0.8 g of the aminoated MXene prepared in Preparation Example 1 was ultrasonically dispersed in 100 mL of deionized water to obtain an aminoated MXene dispersion; 1 g of benzaldehyde was added to the aminoated MXene dispersion and stirred thoroughly at room temperature to obtain a benzaldehyde-grafted MXene-based anode material.

[0052] Comparative Example 1 The specific preparation steps of an MXene-based anode material are as follows: 0.8 g of the aminated MXene prepared in Preparation Example 1 was ultrasonically dispersed in 100 mL of deionized water to obtain an aminated MXene dispersion, which is the MXene-based anode material in this example.

[0053] Comparative Example 2 A formaldehyde-grafted MXene-based anode material is prepared using the following steps: 0.8 g of the aminated MXene prepared in Preparation Example 1 was ultrasonically dispersed in 100 mL of deionized water to obtain an aminated MXene dispersion; 4 g of formaldehyde was added to the aminated MXene dispersion and stirred thoroughly to obtain a formaldehyde-grafted MXene-based anode material.

[0054] Comparative Example 3 The specific preparation steps of a terephthalaldehyde-grafted MXene-based anode material are as follows: 0.8 g of the aminated MXene prepared in Preparation Example 1 was ultrasonically dispersed in 100 mL of deionized water to obtain an aminated MXene dispersion; 4 g of terephthalaldehyde was added to the aminated MXene dispersion and stirred thoroughly to obtain a terephthalaldehyde-grafted MXene-based anode material.

[0055] Performance testing Sodium-ion batteries were fabricated using the MXene-based anode materials prepared in Examples 1-3 and Comparative Examples 1-3, respectively, as electrode active materials. Capacity cycling tests were performed on each sodium-ion battery using a Land battery testing system, and impedance tests were performed using an electrochemical workstation. The specific preparation steps of the above sodium-ion batteries are as follows: (1) The active electrode material, conductive agent carbon black (Super-P) and binder polyvinylidene fluoride (PVDF) with a mass ratio of 80:10:10 are ground and mixed evenly. N-methylpyrrolidone is measured with a syringe as a solvent to make a slurry and obtain the negative electrode slurry.

[0056] (2) The above negative electrode slurry is stirred evenly on a magnetic stirrer for 8h to 10h, then evenly coated on copper foil, and allowed to dry on its surface. Then it is dried overnight in a vacuum oven at 80℃ to obtain a circular negative electrode sheet with a diameter of 12mm.

[0057] (3) In a glove box filled with Ar, the above negative electrode sheet is assembled to obtain a button cell of model 2032; glass fiber is used as the separator material of the battery, sodium sheet is used as the counter electrode and reference electrode in the battery, and 1M NaFP6inDIGLYME=100 vol% is used as the electrolyte of the battery.

[0058] Test results are available Figures 1-4 .

[0059] Figure 1 This is a specific capacity-cycle count graph for batteries prepared using the materials of Examples 1-3 and Comparative Example 1. (From...) Figure 1 It can be observed that at a current density of 0.01 A / g, the initial discharge specific capacities of Examples 1-3 and Comparative Example 1 are 467.4 mAh / g, 322.8 mAh / g, 295.6 mAh / g and 129.5 mAh / g, respectively, and after 200 cycles, their discharge specific capacities are 124.0 mAh / g, 84.3 mAh / g, 75 mAh / g and 51.9 mAh / g, respectively, with capacity retention rates of 26.5%, 26.1%, 28.9% and 40.0%, respectively.

[0060] Figure 2 The images show the initial charge-discharge curves of the batteries prepared using the materials from Examples 1-3 and Comparative Example 1. Figure 2 It can be observed that in the first charge-discharge curves, the DC resistance of Examples 1 to 3 is all less than that of Comparative Example 1. Among them, the DC resistance of Example 1 is the smallest, which is beneficial to improving the discharge capacity of the material.

[0061] Figure 3 Impedance diagrams of batteries prepared from the materials of Examples 1-3 and Comparative Example 1 after 200 cycles. Figure 3 It can be observed that the impedance values ​​of Examples 1 to 3 are all less than those of Comparative Example 1, which indicates that the introduction of benzaldehyde expands the interlayer spacing (1.01nm-1.21nm), which is beneficial to the insertion and extraction of sodium ions.

[0062] Figure 4The specific capacity-cycle count graphs are shown for batteries prepared using the materials of Example 1 and Comparative Examples 2-3. Figure 4 It can be observed that at a current density of 0.01 A / g, the initial discharge specific capacities of Example 1 and Comparative Examples 2-3 are 467.4 mAh / g, 394.3 mAh / g, and 419.0 mAh / g, respectively. After 200 cycles, their discharge specific capacities are 124.0 mAh / g, 92.8 mAh / g, and 96.9 mAh / g, respectively, with capacity retention rates of 26.5%, 23.5%, and 23.1%, respectively. Therefore, compared to graft modification with other aldehydes such as formaldehyde and terephthalaldehyde, the graft modification of benzaldehyde with aminoated MXene in this invention can better improve ion diffusion capacity, capacity performance, and cycle performance.

[0063] In this invention, novel anode materials were prepared under suitable reaction conditions and applied as anode materials for sodium-ion batteries. Taking Example 1 as an example, amino-modified MXene with abundant active sites was first prepared, and then compounded with benzaldehyde through simple mixing to achieve grafting engineering, thereby effectively improving the ion diffusion capacity. Its reversible capacity during cycling was also improved compared to amino-modified MXene, and this also provides a new preparation approach for MXene-based compound anode materials, offering valuable insights for the synthesis of high-capacity anode materials.

[0064] In summary, this invention utilizes the potential active sites on the surface of aminated MXene to graft it with benzaldehyde. This process imparts a larger interlayer spacing to the material without disrupting its unique layered structure, significantly improving its structural stability and oxidation resistance. It also accelerates sodium ion transport kinetics, enhancing its rate performance and long-cycle stability as an anode material, and greatly improving its long-term rapid charge-discharge capability. This invention leverages the synergistic effect of two modification strategies—amination and benzaldehyde grafting—to significantly improve the electrochemical performance of MXene-based anode materials, thereby enabling the production of high-performance anodes and sodium-ion batteries.

Claims

1. An MXene-based anode material, characterized in that, The MXene-based anode material is obtained by grafting benzaldehyde with amino-modified MXene.

2. The MXene-based anode material according to claim 1, characterized in that, The mass ratio of the aminated MXene to the benzaldehyde is 1:(1~10).

3. The MXene-based anode material according to claim 1, characterized in that, The aminated MXene is prepared by a method comprising the following steps: mixing MXene, a surface modifier and water, and reacting to obtain the aminated MXene; the surface modifier includes ammonium salts, ammonia, or combinations thereof.

4. The MXene-based anode material according to claim 3, characterized in that, The ratio of MXene to water is (0.03~0.3) g: 100 mL; And / or, the mass ratio of MXene to the surface modifier is 1:(1~3).

5. The MXene-based anode material according to claim 3, characterized in that, The ammonium salt is selected from ammonium fluoride; And / or, the MXene is obtained by etching Ti3AlC2 with a fluorine-containing reagent.

6. The MXene-based anode material according to claim 1, characterized in that, The MXene-based anode material is a layered material with an interlayer spacing of 1~1.3 nm.

7. A method for preparing an MXene-based anode material as described in any one of claims 1 to 6, characterized in that, The process includes the following steps: mixing benzaldehyde, amino-modified MXene, and water, and performing a Schiff base reaction to obtain the MXene-based anode material.

8. The preparation method according to claim 7, characterized in that, The ratio of aminated MXene to water is (0.2~1.2) g: 100 mL.

9. A negative electrode, characterized in that, The negative electrode comprises a negative electrode current collector and a negative electrode active layer stacked together; the negative electrode active layer comprises the MXene-based negative electrode material according to any one of claims 1 to 6.

10. A sodium-ion battery, characterized in that, The sodium-ion battery includes a positive electrode, a negative electrode, and an electrolyte; the negative electrode includes the MXene-based negative electrode material according to any one of claims 1 to 6.

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