A bimetallic alloy-MXene lithium-sulfur battery separator modification material and a preparation method thereof

Abstract

The application belongs to the technical field of lithium-sulfur batteries, and particularly relates to a bimetallic alloy-MXene lithium-sulfur battery diaphragm modification material and a preparation method thereof. A MAX phase precursor is uniformly ground with NaCl and KCl, then metal chloride powder is added for mixing, and after heating reaction, the product is washed, suction-filtered and dried to obtain the bimetallic alloy-MXene lithium-sulfur battery diaphragm modification material. The bimetallic alloy-MXene has a good physical blocking effect and can effectively inhibit the shuttling of polysulfides. The bimetallic alloy is in a nanoparticle size and is closely combined with MXene, thereby providing multiple reaction sites and helping to improve the conversion of polysulfides and finally improve the electrochemical performance. In addition, due to the synergistic effect of the bimetallic alloy, as an electrocatalyst, the bimetallic alloy can promote the conversion of polysulfides in the charging and discharging process, accelerate the reaction kinetics, and improve the cycle stability and rate performance of the battery.

Description

Technical Field

[0001] This invention belongs to the field of lithium-sulfur battery technology, specifically relating to a bimetallic alloy-MXene lithium-sulfur battery separator modification material and its preparation method. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] With rapid societal development and rising living standards, the demand for portable electronic devices, electric vehicles, and large-scale energy storage equipment is constantly increasing. However, the current lithium-ion battery market is limited by resource scarcity and theoretical specific capacity, making it difficult to meet actual market demands. Therefore, developing energy storage devices with high energy density and long cycle life is crucial. Lithium-sulfur batteries, due to their high energy density (2600Wh / kg), are particularly important. -1 Lithium-sulfur batteries are considered one of the most promising batteries due to their high specific capacity (1675 mAh / g). However, for commercial development, lithium-sulfur batteries still face several thorny problems: (1) The low conductivity of sulfur limits electron transfer, resulting in slow redox kinetics. (2) The volume change of more than 80% in the sulfur cathode during lithiation and delithiation leads to electrode pulverization. (3) The polysulfides intermediate in lithium-sulfur batteries dissolve in the electrolyte and generate a shuttle effect, diffusing through the separator to the negative electrode, causing irreversible loss of effective materials in the electrode, resulting in battery life degradation and low coulombic efficiency. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a bimetallic alloy-MXene lithium-sulfur battery separator modification material and its preparation method. This invention coats a commercial separator with a bimetallic alloy-MXene, leveraging the synergistic effect of MXene and the bimetallic alloy to catalyze the conversion of polysulfides and suppress the shuttle effect of polysulfides, thereby improving the reaction kinetics of the lithium-sulfur battery and enabling the assembled battery to exhibit excellent cycle stability and rate performance.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0006] In a first aspect, the present invention provides a method for preparing a bimetallic alloy-MXene lithium-sulfur battery separator modification material, comprising the following steps:

[0007] After grinding the MAX phase precursor with NaCl and KCl evenly, metal chloride powder was added and mixed. After heating and reacting, the product was washed, filtered and dried to obtain the bimetallic alloy-MXene lithium-sulfur battery separator modification material.

[0008] Preferably, the MAX phase precursor includes at least one of Ti3AlC2, Ti2AlC, Ti2AlN, Ti4AlN3, Nb2AlC, Nb4AlC3, Hf2AlC, Hf2AlN, Mo2AlC, Ta3AlC2, Ta3AlC3, Cr2AlC, Sc2AlC, Zr2AlC, V2AlC, Ti2GaC, V2GaC, Mo2GaN, Ti3SiC2, and Zr2SnC.

[0009] Preferably, the mass ratio of the MAX phase precursor to NaCl and KCl is 1:2-4:2-4.

[0010] Preferably, the metal chloride includes two of the following: cobalt chloride, ferric chloride, ferrous chloride, nickel chloride, copper chloride, manganese chloride, chromium chloride, zinc chloride, tin chloride, gallium chloride, cadmium chloride, indium chloride, and silver chloride.

[0011] Preferably, the ratio of the MAX phase precursor to the metal chloride is 1:0.5-1.5.

[0012] Preferably, the heating reaction temperature is 550-850℃, the time is 6-48h, and the heating atmosphere is an inert atmosphere.

[0013] In a second aspect, the present invention provides a bimetallic alloy-MXene lithium-sulfur battery separator modification material, which is obtained by the preparation method described in the first aspect.

[0014] Thirdly, the present invention provides a method for preparing a bimetallic alloy-MXene modified lithium-sulfur battery separator, comprising the following steps:

[0015] The bimetallic alloy-MXene lithium-sulfur battery separator modification material as described in the second aspect is mixed with a conductive agent and a binder and added to an organic solvent to form a slurry. The slurry is coated on the surface of the separator and dried to obtain the bimetallic alloy-MXene modified lithium-sulfur battery separator.

[0016] Fourthly, the present invention provides a bimetallic alloy-MXene modified lithium-sulfur battery separator, which is obtained by the preparation method described in the third aspect.

[0017] Fifthly, the present invention provides a lithium-sulfur battery comprising a lithium-sulfur battery separator modified with a bimetallic alloy-MXene as described in the fourth aspect.

[0018] The beneficial effects achieved by one or more technical solutions of the present invention are as follows:

[0019] The bimetallic alloy MXene exhibits excellent physical barrier properties, effectively suppressing polysulfide shuttle. The bimetallic alloy, at the nanoparticle size and tightly bound to MXene, provides multiple reaction sites, facilitating polysulfide conversion and ultimately improving electrochemical performance. Furthermore, due to the synergistic effect of the bimetallic alloy, it can act as an electrocatalyst to promote polysulfide conversion during charge and discharge processes, accelerating reaction kinetics and enhancing battery cycle stability and rate performance.

[0020] The bimetallic alloy-MXene synthesis method is a one-step synthesis that eliminates the need for strong acids and bases, making it environmentally friendly and significantly reducing synthesis time and experimental costs. Modified membranes can be prepared using a coating method based on commercial thin films, which is simple, easy to operate, and scalable to large-scale practical production applications. Attached Figure Description

[0021] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0022] Figure 1 This is the XRD pattern of Co3Fe7-MXene prepared in Example 1 of this invention.

[0023] Figure 2 This is a SEM image of Co3Fe7-MXene prepared in Example 1 of this invention.

[0024] Figure 3 These are physical images (left) of a commercially available separator and (right) of a Co3Fe7-MXene-modified lithium-sulfur battery separator prepared in Example 1 of this invention.

[0025] Figure 4 This is a cycle performance test diagram of a 2032 coin-type lithium-sulfur battery assembled using the Co3Fe7-MXene modified lithium-sulfur battery separator prepared in Example 1 of this invention.

[0026] Figure 5 This is a rate performance test diagram of a 2032 coin-type lithium-sulfur battery assembled using the Co3Fe7-MXene modified lithium-sulfur battery separator prepared in Example 1 of this invention. Detailed Implementation

[0027] Lithium-sulfur batteries, as a novel battery technology, have attracted widespread attention and research due to their high energy density and low cost. However, the commercialization of lithium-sulfur batteries has been delayed for several reasons, the main one being the shuttle effect of polysulfides dissolved in the electrolyte during battery cycling. Furthermore, the slow conversion kinetics of dissolved lithium polysulfides lead to a sharp capacity decay during battery cycling, failing to meet the requirements for commercial use.

[0028] The bimetallic alloy-MXene lithium-sulfur battery separator modification material of this invention provides physical barriers and adsorption for lithium polysulfide shuttle, thereby suppressing the shuttle effect. Furthermore, the synergistic effect of MXene and the bimetal can effectively catalyze the conversion of polysulfides. The addition of conductive materials improves the conductivity of the separator, and the uniform distribution of bimetallic particles on the MXene surface provides more transport sites, accelerating ion and electron transport, thereby enhancing the reaction kinetics of the lithium-sulfur battery and enabling the assembled battery to exhibit excellent cycle stability and rate performance.

[0029] This invention uses a simple coating method to coat a bimetallic alloy-MXene lithium-sulfur battery separator modification material onto a commercial separator, leveraging the synergistic effect of MXene and the bimetallic alloy to catalyze the conversion of polysulfides and suppress the shuttle effect of polysulfides, thereby improving the reaction kinetics of the lithium-sulfur battery and enabling the assembled battery to exhibit excellent cycle stability and rate performance.

[0030] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments and comparative examples.

[0031] Example 1

[0032] MAX phase-Ti3AlC2 powder was mixed uniformly with NaCl and KCl in a glove box under nitrogen protection. Then, FeCl2 and CoCl2 (in a ratio of 3:9:9:2:1) were added and mixed uniformly. The mixture was then ground in a mortar for 30 minutes. The powder mixture was transferred to a crucible and heated to 750°C in a tube furnace under inert gas protection for 24 hours. The product was then washed with deionized water, vacuum filtered, and dried at 50°C for 12 hours to obtain Co3Fe7-MXene. Co3Fe7-MXene was mixed with Super P and polyvinylidene fluoride (PVDF) at a mass ratio of 8:1:1 and uniformly dispersed in N-methylpyrrolidone (NMP) to prepare a slurry. This slurry mixture was then coated onto the surface of a separator and vacuum dried at 50°C for 12 hours to obtain the Co3Fe7-MXene-modified lithium-sulfur battery separator.

[0033] A Co3Fe7-MXene-modified lithium-sulfur battery separator, along with commercial lithium-sulfur battery electrolyte, lithium metal sheets, gaskets, and positive and negative electrode shells, were stacked and assembled to form a 2032-type coin cell. An unmodified separator, along with commercial lithium-sulfur battery electrolyte, lithium metal sheets, gaskets, and positive and negative electrode shells, was also stacked and assembled to form a 2032-type coin cell as a control.

[0034] Figure 1The XRD pattern of Co3Fe7-MXene prepared in Example 1 is shown, indicating that Co3Fe7 was successfully loaded onto MXene and the material was successfully prepared.

[0035] Figure 2 SEM images of the Co3Fe7-MXene prepared in Example 1 are shown, indicating that the Co3Fe7 alloy is dispersed on the MXene surface and in the interlayer spaces.

[0036] Figure 3 Commercial separators (left) and lithium-sulfur battery separators modified with Co3Fe7-MXene powder prepared in Example 1 (right) are shown, demonstrating that the powder has been uniformly coated onto the surface of the commercial separator.

[0037] Figure 4 The cycling performance test of a 2032-type coin lithium-sulfur battery assembled with a Co3Fe7-MXene-modified lithium-sulfur battery separator is shown. As can be seen from the figure, the lithium-sulfur battery still has a discharge specific capacity of 491.48 mAh / g after 400 cycles, which is significantly higher than the discharge specific capacity of the lithium-sulfur battery assembled with the blank separator (233.83 mAh / g), achieving high energy density.

[0038] Figure 5 The rate performance test of a 2032-type coin-type lithium-sulfur battery assembled with a Co3Fe7-MXene modified lithium-sulfur battery separator is shown. As can be seen from the figure, the lithium-sulfur battery has very good rate performance.

[0039] Example 2

[0040] MAX phase-Ti3AlC2 powder was mixed uniformly with NaCl and KCl in a glove box under nitrogen protection. Then, FeCl2 and CoCl2 (in a ratio of 3:9:9:2:1) were added and mixed uniformly. The mixture was then ground in a mortar for 30 minutes. The powder mixture was transferred to a crucible and heated to 850°C in a tube furnace under inert gas protection for 24 hours. The product was then washed with deionized water, vacuum filtered, and dried at 50°C for 12 hours to obtain Co3Fe7-MXene. Co3Fe7-MXene was mixed with Super P and polyvinylidene fluoride (PVDF) at a mass ratio of 8:1:1 and uniformly dispersed in N-methylpyrrolidone (NMP) to prepare a slurry. This slurry mixture was then coated onto the surface of a separator and vacuum dried at 50°C for 12 hours to obtain the Co3Fe7-MXene-modified lithium-sulfur battery separator.

[0041] The Co3Fe7-MXene-modified lithium-sulfur battery separator, commercial lithium-sulfur battery electrolyte, lithium metal sheet, gasket, and positive and negative electrode shells are stacked and assembled, and then sealed to form a 2032 coin cell.

[0042] Example 3

[0043] MAX phase-Ti3AlC2 powder was mixed uniformly with NaCl2 and KCl in a glove box under nitrogen protection. Then, FeCl2 and CoCl2 (in a ratio of 2:6:6:1:1) were added and mixed thoroughly. The mixture was then ground in a mortar for 30 minutes. The powder mixture was transferred to a crucible and heated to 750°C in a tube furnace under inert gas protection for 24 hours. Subsequently, the powder was washed with deionized water, vacuum filtered, and dried at 50°C for 12 hours to obtain CoFe-MXene. CoFe-MXene was mixed with Super P and polyvinylidene fluoride (PVDF) at a mass ratio of 8:1:1 and uniformly dispersed in N-methylpyrrolidone (NMP) to prepare a slurry. The slurry mixture was then coated onto the surface of a separator and vacuum dried at 50°C for 12 hours to obtain the CoFe-MXene-modified lithium-sulfur battery separator.

[0044] The CoFe-MXene-modified lithium-sulfur battery separator, commercial lithium-sulfur battery electrolyte, lithium metal sheet, gasket, and positive and negative electrode shells are stacked and assembled, and then sealed to form a 2032 coin cell.

[0045] Example 4

[0046] MAX phase-Ti3AlC2 powder was mixed uniformly with NaCl and KCl in a glove box under nitrogen protection. FeCl2 and CuCl2 were then added and mixed uniformly in a ratio of 2:6:6:1:1. The mixture was ground in a mortar for 30 minutes. The powder mixture was then transferred to a crucible and heated to 750°C in a tube furnace under inert gas protection for 24 hours. Subsequently, the powder was washed with deionized water, vacuum filtered, and dried at 50°C for 12 hours to obtain FeCu-MXene. FeCu-MXene powder was mixed with Super P and polyvinylidene fluoride (PVDF) at a mass ratio of 8:1:1 and uniformly dispersed in N-methylpyrrolidone (NMP) to prepare a slurry. This slurry mixture was then coated onto the surface of a separator and vacuum dried at 50°C for 12 hours to obtain the FeCu-MXene-modified lithium-sulfur battery separator.

[0047] The FeCu-MXene modified lithium-sulfur battery separator, commercial lithium-sulfur battery electrolyte, lithium metal sheet, gasket, and positive and negative electrode shells are stacked and assembled, and then sealed to form a 2032 coin cell.

[0048] Example 5

[0049] MAX phase-Ti3AlC2 powder was mixed with NaCl and KCl under nitrogen protection in a glove box until homogeneous. CoCl2 and CuCl2 were then added and mixed thoroughly (ratio 2:6:6:1:1). The mixture was ground in a mortar for 30 minutes. The powder was then transferred to a crucible and heated to 750°C in a tube furnace under inert gas protection for 24 hours. The mixture was then washed with deionized water, vacuum filtered, and dried at 50°C for 12 hours to obtain CoCu-MXene. CoCu-MXene powder was mixed with Super P and polyvinylidene fluoride (PVDF) at a mass ratio of 8:1:1 and uniformly dispersed in N-methylpyrrolidone (NMP) to prepare a slurry. This slurry mixture was then coated onto the surface of a separator and vacuum dried at 50°C for 12 hours to obtain the CoCu-MXene-modified lithium-sulfur battery separator.

[0050] The CoCu-MXene-modified lithium-sulfur battery separator, commercial lithium-sulfur battery electrolyte, lithium metal sheet, gasket, and positive and negative electrode shells are stacked and assembled, and then sealed to form a 2032 coin cell.

[0051] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a bimetallic alloy-MXene lithium-sulfur battery separator modification material, characterized in that, Includes the following steps: After grinding the MAX phase precursor with NaCl and KCl evenly, metal chloride powder was added and mixed. After heating and reacting, the product was washed, filtered and dried to obtain the bimetallic alloy-MXene lithium-sulfur battery separator modification material. The mass ratio of the MAX phase precursor to NaCl and KCl is 1:2-4:2-4; The metal chlorides include two of the following: cobalt chloride, ferric chloride, ferrous chloride, nickel chloride, copper chloride, manganese chloride, chromium chloride, zinc chloride, tin chloride, gallium chloride, cadmium chloride, indium chloride, and silver chloride. The ratio of the MAX phase precursor to the metal chloride is 1:0.5-1.5; The heating reaction is carried out at a temperature of 550-850 ℃ for 6-48 h, and the heating atmosphere is an inert atmosphere.

2. The preparation method according to claim 1, characterized in that, The MAX phase precursor includes at least one of Ti3AlC2, Ti2AlC, Ti2AlN, Ti4AlN3, Nb2AlC, Nb4AlC3, Hf2AlC, Hf2AlN, Mo2AlC, Ta3AlC2, Ta3AlC3, Cr2AlC, Sc2AlC, Zr2AlC, V2AlC, Ti2GaC, V2GaC, Mo2GaN, Ti3SiC2, and Zr2SnC.

3. A bimetallic alloy-MXene lithium-sulfur battery separator modification material, characterized in that, Obtained by the preparation method as described in any one of claims 1-2.

4. A method for preparing a bimetallic alloy-MXene modified lithium-sulfur battery separator, characterized in that, Includes the following steps: The bimetallic alloy-MXene lithium-sulfur battery separator modification material as described in claim 3 is mixed with a conductive agent and a binder and added to an organic solvent to form a slurry. The slurry is coated on the surface of the separator and dried to obtain the bimetallic alloy-MXene modified lithium-sulfur battery separator.

5. A bimetallic alloy-MXene modified lithium-sulfur battery separator, characterized in that, Obtained by the preparation method described in claim 4.

6. A lithium-sulfur battery, characterized in that, Including the bimetallic alloy-MXene modified lithium-sulfur battery separator as described in claim 5.

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