An interface structure material of nitrogen and nickel co-doped MXene in-situ derived titanium dioxide and a preparation method thereof

Abstract

The application discloses an interface structure material of nitrogen-nickel co-doped MXene in-situ derived titanium dioxide and a preparation method thereof. The application takes the nitrogen-nickel co-doped MXene derived TiO2 interface structure composite material as a carrier, and fuses a main sulfur body material with the active sulfur. The method comprises the following steps: firstly, preparing a MXene colloidal solution, and then preparing a Ni-doped MXene precursor; secondly, mixing the Ni-doped MXene precursor with an ammonium salt, and obtaining N-Ni MXene@ATiO2 (N-Ni M@AT), N-Ni MXene@RTiO2 (N-Ni M@RT) and N-Ni MXene@ARTiO2 (N-Ni M@ART) materials through calcination at different temperatures; and finally, preparing a sulfur positive electrode material through a solid-state melting method. The material can chemisorb and efficiently catalyze the reversible conversion of polysulfides, and improve the utilization rate of active sulfur. A lithium-sulfur battery assembled with the material as a cathode can effectively inhibit the dissolution and shuttling of polysulfides, and exhibits excellent electrochemical performance. The preparation method has universality, is simple and easy to operate, and is efficient in preparation, and has a wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of novel energy materials technology, and specifically relates to an interfacial structure material of in-situ derived titanium dioxide by nitrogen-nickel co-doping MXene and its preparation method. Background Technology

[0002] Lithium-sulfur batteries based on multiphase sulfur conversion reactions have a capacity of 1675 mAh g. -1 High theoretical specific capacity and 2600Wh / kg -1 High energy density, along with environmental friendliness and economic efficiency, has made Li-S batteries one of the most promising candidates for meeting emerging energy storage needs. Despite their attractive advantages, Li-S batteries suffer from significant drawbacks due to the insulating properties of sulfur and lithium sulfides, large volume expansion during the reaction, and the formation of soluble intermediate polysulfides (LiPSs, Li2S). n The shuttle effect induced by (n=4-8) and the slow sulfur redox kinetics contribute to low sulfur utilization and short cycle life. Significant challenges remain regarding its large-scale practical application.

[0003] Over the past few decades, researchers have devoted considerable effort to addressing the critical issue of the "shuttle effect" in lithium-sulfur batteries. Initially, a range of carbon materials with specific structures (carbon spheres, carbon nanotubes, graphene, etc.) were widely used as sulfur hosts in cathodes due to van der Waals forces and spatial advantages. However, the nonpolar surfaces of carbon materials exhibit weak interactions with LiPSs, and under high sulfur mass loading conditions, the volume of carbon-based cathodes expands dramatically, leading to a decrease in the rate capability of lithium-sulfur batteries. Therefore, the rational design of sulfur host materials with synergistic catalytic functions that possess high adsorption activity and rapidly convert LiPSs is crucial for achieving high-performance Li-S batteries. Summary of the Invention

[0004] To address the aforementioned technical problems, the present invention aims to overcome the shortcomings of existing technologies and provide an interface structure material of in-situ derived titanium dioxide from nitrogen-nickel co-doped MXene and its preparation method. The material prepared by this invention, through the construction of a homojunction, possesses a nearly perfect lattice-matched identical material composition, exhibiting faster charge transfer and electronic conductivity than heterojunctions. This effectively suppresses the shuttle effect in lithium-sulfur batteries and promotes the sulfur conversion reaction. Simultaneously, a method for its preparation is provided.

[0005] The technical solution provided by this invention is as follows:

[0006] In a first aspect, the present invention provides a method for preparing an interfacial structure material of in-situ derived titanium dioxide co-doped with nitrogen and nickel MXene, comprising the following steps:

[0007] (1) Preparation of MXene colloidal solution;

[0008] (2) Preparation of Ni-doped MXene precursor: Add MXene colloidal solution to nickel salt solution, stir and react, and then freeze dry to obtain the precursor.

[0009] (3) The Ni-doped MXene precursor was mixed with ammonium salt and calcined in a protective atmosphere to obtain an interface structure material.

[0010] Furthermore, in step (1), the preparation method of the MXene colloidal solution is as follows: lithium fluoride is added to hydrochloric acid to form a mixed solution, and the MAX phase is added to react to obtain the solution.

[0011] Furthermore, the MAX phase includes one of Ti3AlC2, Nb2AlC and V2AlC, and the corresponding MXene is one of Ti3C2, Nb2C and V2C.

[0012] Furthermore, in step (1), the mass ratio of lithium fluoride to the MAX phase is 1.5-3g:1-2g.

[0013] Furthermore, in step (2), the nickel salt includes one of NiCl, NiSO4, and Ni(NO3)2.

[0014] Furthermore, in step (2), the concentration of the MXene colloidal solution is 5-20 mg / mL, and the concentration of the nickel salt solution is 2-6 mg / mL; the ratio of the amount of MXene colloidal solution to the amount of nickel salt solution is 10-20 mL: 250-500 μL.

[0015] Furthermore, in step (3), the ratio of Ni-doped MXene precursor to ammonium salt is 100-200 mg: 1-2 g.

[0016] Furthermore, in step (3), the ammonium salt is selected from one of ammonium chloride, ammonium nitrate, ammonium sulfate, and ammonium carbonate.

[0017] Furthermore, in step (3), different surface structure materials are obtained by controlling the calcination temperature, as follows:

[0018] (1) Calcination temperature 400-500℃ to obtain N-Ni M@AT material;

[0019] (2) Calcination temperature 600-700℃ to obtain N-Ni M@ART material;

[0020] (3) Calcination temperature 800-1000℃ to obtain N-Ni M@RT material.

[0021] This invention employs a novel method combining co-doping and interface engineering to prepare a sulfur host material for synergistic catalysis of LiPSs, serving as the cathode for high-performance lithium-sulfur batteries. The conductive framework of titanium-based MXene nanosheets co-doped with "sulfophilic" nickel and "lithophile" nitrogen atoms forms dual anchoring sites, and TiO2 interface structures, including N-NiM@AT, N-Ni M@RT, and N-Ni M@ART structures, are derived in situ on the nanosheets. This material, exhibiting synergistic catalytic activity, can effectively suppress the shuttle effect and promote sulfur conversion reactions when used as a sulfur cathode in lithium-sulfur batteries, providing important guidance for next-generation high-performance lithium-sulfur batteries.

[0022] In a second aspect, the present invention provides an interface structure material of in-situ derived titanium dioxide co-doped with MXene and prepared by the method described in the first aspect.

[0023] Thirdly, the present invention provides a cathode material: prepared by loading sulfur onto the interface structure material described in the second aspect using a solid-state melting method.

[0024] Fourthly, the present invention provides the application of the cathode material described in the third aspect in lithium-sulfur batteries.

[0025] The beneficial effects of this invention are as follows:

[0026] The nitrogen-nickel co-doped MXene in-situ derived TiO2 interface structure material of this invention exhibits faster charge transfer and electronic conductivity than heterojunctions by constructing a homojunction while simultaneously adsorbing polysulfides and catalytically converting them.

[0027] The material described in this invention, used as a sulfur cathode material in lithium-sulfur batteries, synergistically suppresses the shuttle effect and promotes the sulfur conversion reaction, significantly improving the energy storage capacity and cycle life of lithium-sulfur batteries. Furthermore, this invention offers numerous advantages such as low cost, simple operation, and wide applicability, providing important guidance for the next generation of high-performance lithium-sulfur batteries.

[0028] The interface structure material described in this invention is used to prepare electrode sheets and assemble lithium-sulfur batteries. The resulting battery has an initial capacity of 1280 mAh / g at 0.1C and maintains a high reversible capacity after 150 charge-discharge cycles at 1C. Attached Figure Description

[0029] Figure 1 The X-ray diffraction pattern (XRD pattern) of the in-situ derived TiO2 homojunction material with nitrogen-nickel co-doped MXene.

[0030] Figure 2 Transmission electron microscope (TEM) image of the in-situ derived TiO2 homojunction material with nitrogen-nickel co-doped MXene. Detailed Implementation

[0031] The present invention will now be described in detail with reference to the embodiments, but the scope of protection of the present invention is not limited to the following embodiments.

[0032] Example 1

[0033] I. Preparation of interfacial structure materials for in-situ derived titanium dioxide from nitrogen-nickel co-doped MXene, the steps are as follows:

[0034] (1) In-situ generation of hydrofluoric acid etching method to prepare MXene nanosheet colloidal solution, including the following sub-steps:

[0035] Hydrofluoric acid is generated in situ from lithium fluoride and hydrochloric acid; wherein the amount of lithium fluoride is 1.6 g, the concentration of hydrochloric acid is 9 M, and the volume is 20 mL;

[0036] The MAX phase raw material was selected, and 1g of Ti3AlC2 was used as the etching raw material; the reaction time was 48h; the magnetic stirring speed was 1000rpm; and the water bath reaction temperature was 35℃.

[0037] Perform centrifugal washing, using 0.1M dilute hydrochloric acid and deionized water sequentially, centrifuging and washing, and pouring out the supernatant until the pH of the supernatant is neutral. Then retain it and centrifuge to expand. The number of times to wash with dilute hydrochloric acid is 2-3 times and the number of times to wash with deionized water is 12 times; the centrifugation speed is 3500 rpm.

[0038] The mixture after centrifugation and expansion was passed through a protective gas and sonicated at low temperature for 2 hours, with the water bath temperature at 10℃ and the ultrasonic power at 200W. After centrifugation for 1 hour, the upper liquid was retained to obtain an MXene nanosheet colloidal solution.

[0039] (2) Preparation of Ni-doped MXene precursor: Take 20 mL of the colloidal solution obtained in step (1) and add 500 μL of a solution with a concentration of 4 mg / mL. -1 Ni-doped MXene precursor powder can be obtained by stirring a NiCl solution for 12 hours and then freeze-drying it in a freeze dryer for 48 hours.

[0040] (3) The precursor powder obtained in step (2) is mixed and ground with 1g of ammonium chloride and then heat-treated in an argon atmosphere in a tube furnace for 2h to obtain N-Ni M@AT material at a heat treatment temperature of 500℃.

[0041] II. Preparation of cathode material and electrode sheet, the steps are as follows:

[0042] (1) Using solid-state melting to load sulfur, the N-Ni M@AT material obtained in the above steps is mixed with sublimed sulfur powder and heat-treated at 155°C for 2 hours in a tube furnace under a nitrogen atmosphere to obtain N-Ni M@AT-S cathode material.

[0043] (2) The N-Ni M@AT-S cathode material obtained in step (1) is mixed with binder and conductive agent in a certain proportion and stirred for 12 hours to obtain cathode slurry. It is then uniformly coated on aluminum foil and dried for 12 hours to obtain electrode sheet.

[0044] III. Assembling Lithium-Sulfur Batteries

[0045] Electrode sheets were fabricated from the sample and assembled into a lithium-sulfur battery. The initial capacity was measured to be 1185.53 mAh g⁻¹ at a current density of 0.1C. -1 After 150 charge-discharge cycles, the remaining capacity is 496.1 mAh g. -1 It has a capacity retention rate of 41.8%.

[0046] Example 2

[0047] I. Preparation of interfacial structure materials for in-situ derived titanium dioxide from nitrogen-nickel co-doped MXene, the steps are as follows:

[0048] (1) MXene nanosheet colloidal solution was prepared in situ by the method in step (1) of Example 1 using hydrofluoric acid etching;

[0049] (2) Preparation of Ni-doped MXene precursor: Take 20 mL of the colloidal solution obtained in step (1) and add 500 μL of a solution with a concentration of 4 mg / mL. -1 Ni-doped MXene precursor powder can be obtained by stirring a NiCl solution for 12 hours and then freeze-drying it in a freeze dryer for 48 hours.

[0050] (3) The precursor powder obtained in step (2) is mixed and ground with 1g of ammonium chloride and then heat-treated in an argon atmosphere in a tube furnace for 2h to obtain N-Ni M@ART material at a heat treatment temperature of 600℃-700℃.

[0051] II. Preparation of cathode material and electrode sheet, the steps are as follows:

[0052] (1) Using solid-state melting to load sulfur, the N-Ni M@ART material obtained above was mixed with sublimed sulfur powder and heat-treated at 155°C for 2 hours in a tube furnace under a nitrogen atmosphere to obtain N-Ni M@ART-S cathode material.

[0053] (2) The N-Ni M@ART-S cathode material obtained in step (1) is mixed with binder and conductive agent in a certain proportion and stirred for 12 hours to obtain cathode slurry. The slurry is then uniformly coated on aluminum foil and dried for 12 hours to obtain electrode sheet.

[0054] III. Assembling Lithium-Sulfur Batteries

[0055] Electrode sheets were fabricated from the sample and assembled into a lithium-sulfur battery. The initial capacity was measured to be 1280 mAh g at a current density of 0.1C.-1 After 150 charge-discharge cycles, the remaining capacity is 772.5 mAh g. -1 It has a capacity utilization rate of 60.3%.

[0056] Example 3

[0057] I. Preparation of interfacial structure materials for in-situ derived titanium dioxide from nitrogen-nickel co-doped MXene, the steps are as follows:

[0058] (1) MXene nanosheet colloidal solution was prepared in situ by hydrofluoric acid etching method according to step (1) in Example 1.

[0059] (2) Preparation of Ni-doped MXene precursor: Take 20 mL of the colloidal solution obtained in step (1) and add 500 μL of a solution with a concentration of 4 mg / mL. -1 Ni-doped MXene precursor powder can be obtained by stirring a NiCl solution for 12 hours and then freeze-drying it in a freeze dryer for 48 hours.

[0060] (3) The precursor powder obtained in step (2) was mixed and ground with 1g of ammonium chloride and then heat-treated in an argon atmosphere in a tube furnace for 2h to obtain N-Ni M@RT material at a heat treatment temperature of 800℃.

[0061] II. Preparation of cathode material and electrode sheet, the steps are as follows:

[0062] (1) Using solid-state melting to load sulfur, the N-Ni M@RT material obtained above was mixed with sublimed sulfur powder and heat-treated at 155°C for 2 hours in a tube furnace under a nitrogen atmosphere to obtain N-Ni M@RT-S cathode material.

[0063] (2) The N-Ni M@RT-S cathode material obtained in step (1) is mixed with binder and conductive agent in a certain proportion and stirred for 12 hours to obtain cathode slurry. The slurry is then uniformly coated on aluminum foil and dried for 12 hours to obtain electrode sheet.

[0064] III. Assembly of the Lithium-Sulfur Battery: Electrode sheets were prepared from the sample, and a lithium-sulfur battery was assembled. At a current density of 0.1C, the initial capacity was measured to be 1074.19 mAh g. -1 After 150 charge-discharge cycles, the remaining capacity is 490.32 mAh g. -1 It has a capacity retention rate of 45.6%.

[0065] Figure 1 The X-ray diffraction (XRD) patterns of the nitrogen-nickel co-doped MXene in-situ derived TiO2 homojunction materials prepared in the above embodiments are shown below. Figure 1 The successful preparation of MXene, N-Ni M@AT, N-Ni M@ART, and N-Ni M@RT materials can be seen.

[0066] Figure 2 This is a transmission electron microscope (TEM) image of the nitrogen-nickel co-doped MXene in-situ derived TiO2 homojunction material prepared in this embodiment. Figure 2 It can be seen that anatase titanium dioxide (AT) and rutile titanium dioxide (RT) are uniformly distributed on MXene nanosheets.

[0067] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made 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 invention.

Claims

1. A method for preparing an interfacial structure material of in-situ derived titanium dioxide co-doped with nitrogen and nickel MXene, characterized in that, Includes the following steps: (1) Preparation of MXene colloidal solution; The preparation method of the MXene colloidal solution is as follows: lithium fluoride is added to hydrochloric acid to form hydrofluoric acid in situ, and the MAX phase is added to react to obtain the solution. The MAX phase includes Ti3AlC2, and the corresponding MXene is Ti3C2. (2) Preparation of Ni-doped MXene precursor: Add MXene colloidal solution to nickel salt solution, stir and react, and then freeze dry to obtain the precursor; (3) The Ni-doped MXene precursor was mixed with ammonium salt and calcined in a protective atmosphere to obtain an interface structure material.

2. The method for preparing the interface structure material of in-situ derived titanium dioxide from nitrogen-nickel co-doped MXene according to claim 1, characterized in that, In step (1), the mass ratio of lithium fluoride to MAX phase is 1.5-3g:1-2g.

3. The method for preparing the interface structure material of in-situ derived titanium dioxide from nitrogen-nickel co-doped MXene according to claim 1, characterized in that, In step (2), the nickel salt is selected from nickel chloride, nickel nitrate, and nickel sulfate; the concentration of the MXene colloidal solution is 5-20 mg / mL, and the concentration of the nickel salt solution is 2-6 mg / mL; the ratio of the amount of MXene colloidal solution to the amount of nickel salt solution is 10-20 mL: 250-500 μL.

4. The method for preparing the interface structure material of in-situ derived titanium dioxide from nitrogen-nickel co-doped MXene according to claim 1, characterized in that, In step (3), the ratio of Ni-doped MXene precursor to ammonium salt is 100-200 mg: 1-2 g.

5. The method for preparing the interface structure material of in-situ derived titanium dioxide with nitrogen-nickel co-doped MXene according to claim 1, characterized in that, In step (3), the ammonium salt is selected from one of ammonium chloride, ammonium nitrate, ammonium sulfate, and ammonium carbonate.

6. The method for preparing the interface structure material of in-situ derived titanium dioxide from nitrogen-nickel co-doped MXene according to claim 1, characterized in that, In step (3), different interface structure materials are obtained by controlling the calcination temperature, as follows: (1) Calcination temperature 400-500℃ to obtain N-Ni M@AT material; (2) Calcination temperature 600℃-700℃ to obtain N-Ni M@ART material; (3) Calcination temperature 800-1000℃ to obtain N-Ni M@RT material.

7. An interfacial structure material of in-situ derived titanium dioxide co-doped with nitrogen and nickel MXene, characterized in that: Prepared using the method described in any one of claims 1-6.

8. A cathode material, characterized in that: The interface structure material described in claim 7 was prepared by loading sulfur using a solid-state melting method.

9. The application of the cathode material according to claim 8 in lithium-sulfur batteries.

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