An MXene@NiSe2 heterostructure for sulfur host material in lithium-sulfur batteries and its preparation method

Abstract

The application discloses a MXene@NiSe2 heterostructure material for a lithium-sulfur battery sulfur host material and a preparation method thereof.The method is characterized in that: the MXene material is obtained through etching and hand shaking centrifugation on a MAX phase material, and a large number of negative charges on the surface of the material can attract positive metal ions; the MXene material is used as a support material to grow NiSe2 nanoparticles on the surface of the material through further microwave reaction, thereby obtaining the MXene@NiSe2 heterostructure material; when the material is applied to a lithium-sulfur battery sulfur host material, a large number of functional groups on the surface of the MXene material can promote the formation of strong chemical interaction with polysulfides and effectively catalyze the reaction kinetics; the excellent conductivity of the MXene material and the catalytic activity of the NiSe2 material can relieve the "shuttle effect", meanwhile, the contact interface (heterostructure) between the two materials can generate more catalytic / adsorption active sites, promote electron transfer, and improve the rate capability and cycle stability of the battery; and the material prepared by the application can improve the performance of the lithium-sulfur battery and has a large application prospect.

Description

Technical Field

[0001] This invention belongs to the technical field of novel energy electrode materials, specifically relating to an MXene@NiSe2 heterostructure for use as the sulfur host material in lithium-sulfur batteries and its preparation method. Background Technology

[0002] Electrochemical energy storage devices are a key technology for the storage and redistribution of renewable energy. Lithium-sulfur (Li-S) batteries are among the most promising next-generation energy storage devices. Li-S batteries exhibit a capacity of 2567 Wh / kg. -1 The Li-S battery boasts a high theoretical energy density. However, its practical application is hampered by several obstacles. The notorious shuttle effect of long-chain polysulfides, soluble intermediates, leads to severe capacity decay and short cycle life. The insulating properties of sulfur and Li₂S result in insufficient sulfur utilization and poor rate performance. The significant volume difference between S and Li₂S can damage the electrode structure. In recent decades, tremendous efforts have been made to overcome these problems, including physically confining sulfur in porous carbon, chemically bonding LiPS with polar metal compounds, and inserting conductive interlayers between the cathode and separator. These strategies have alleviated the aforementioned problems to some extent, but the commercial application of Li-S batteries has not yet been realized.

[0003] In material systems exhibiting a synergistic "adsorption-catalysis" effect, heterostructure mediators have attracted attention due to their flexible bonding mechanisms and excellent electrical properties. Typically, heterostructures consist of two or more materials; the coupling between these heterogeneous regions generates a synergistic effect, with overall performance far exceeding that of simple material mixing. Unique interfaces endow the materials with distinctive electronic conductivity, strong adsorption, and catalytic activity against LiPSs. Therefore, applying heterostructures to sulfur-based materials can improve the performance of lithium-sulfur batteries.

[0004] Currently, there is a lack of a material with a heterostructure that can be applied to lithium-sulfur batteries and improve their performance. Summary of the Invention

[0005] The purpose of this invention is to address the aforementioned problems by providing an MXene@NiSe2 heterostructure for the sulfur host material in lithium-sulfur batteries, which promotes charge transfer and regulates catalytic activity. The material of this invention possesses a heterostructure; the coupling between these heterogeneous regions generates a synergistic effect, and the unique interface endows the material with unique electronic conductivity, strong adsorption, and catalytic activity for LiPSs. This invention alleviates the shuttle effect in Li-S batteries and promotes sulfur conversion reactions, while also providing a method for its preparation.

[0006] The technical solution provided by this invention is as follows:

[0007] In a first aspect, the present invention provides a method for preparing an MXene@NiSe2 heterostructure material for use as a sulfur host material in lithium-sulfur batteries, comprising the following steps:

[0008] (1) Preparation of MXene nanosheet colloidal solution;

[0009] (2) Preparation of precursor powder: Nickel salt, selenium powder and MXene nanosheet colloidal solution are mixed evenly and dried to form precursor powder;

[0010] (3) After mixing the selenium powder, polymer A and precursor powder, grind them and place them in a small container with a lid; the polymer A is polyacrylonitrile (PAN) or polyvinylpyrrolidone (PVP);

[0011] (4) Place the small container with a lid into a large container with a lid containing microwave absorbing material and carry out a microwave reaction to obtain the product.

[0012] Furthermore, in step (1), the steps for preparing the MXene nanosheet colloidal solution are as follows: lithium fluoride is added to hydrochloric acid and mixed, MAX phase is added, and the solution is obtained after subsequent processing.

[0013] Furthermore, in step (1), the subsequent processing includes: multiple centrifugations and ultrasonic stripping.

[0014] Furthermore, in step (1), the concentration of hydrochloric acid is 9M; the MAX phase is one of Ti3AlC2, Nb2AlC and V2AlC, and the corresponding MXene is one of Ti3C2, Nb2C and V2C.

[0015] Furthermore, in step (1), the mass ratio of lithium fluoride to the MAX phase is 1.5-3g:1-2g.

[0016] Furthermore, the nickel salt is selected from one of nickel chloride, nickel nitrate, and nickel sulfate.

[0017] Furthermore, in step (2), the mass ratio of nickel salt, selenium powder and MXene nanosheet colloidal solution is 100-500mg:200-1000mg:100-500mg; the concentration of the MXene nanosheet colloidal solution is 5-20mg / mL.

[0018] Furthermore, in step (3), the mass of selenium powder, polymer A and precursor powder is 200-1000mg: 50-250mg: 50-250mg.

[0019] Furthermore, in step (4), the microwave absorbing material is a metal oxide, including one of CuO, SnO2, TiO2, and Fe3O4.

[0020] Preferably, the microwave absorbing material is CuO.

[0021] Furthermore, in step (4), the microwave power is 500-1000W and the microwave heating time is 20-40min.

[0022] In a second aspect, the present invention provides an MXene@NiSe2 heterostructure material for use as the sulfur host material in lithium-sulfur batteries, which is prepared by the method described in the first aspect.

[0023] Thirdly, the present invention provides a cathode material obtained by loading sulfur onto the MXene@NiSe2 heterostructure material described in the second aspect using a solid-state melting method.

[0024] The method described in this invention obtains MXene material by etching and centrifuging the MAX phase material. Its surface carries a large number of negative charges, which can attract positively charged metal ions. Using this as a support material, NiSe2 nanoparticles are further grown on its surface via microwave reaction to obtain an MXene@NiSe2 heterostructure material. In the preparation method described in this invention, selenium powder is used in steps (2) and (3). Selenium powder is used in step (2) to ensure uniform mixing with the MXene colloidal solution and nickel salt. Selenium powder is added in step (3) because selenium evaporates during heating; an excess of selenium powder is added here to allow for a thorough reaction with the Ni salt. The MXene@NiSe2 heterostructure prepared in this invention, used as the sulfur host material for lithium-sulfur batteries, has a large number of hydroxyl, fluorine, and oxygen groups modified on its surface. These functional groups can promote strong chemical interactions with LiPSs. The MXene@NiSe2 heterostructure has high conductivity and redox activity, enabling effective electron transfer and improving the conversion kinetics of LiPSs. This enables MXene@NiSe2 to mitigate the shuttle effect and improve the cycle stability of lithium-sulfur batteries when used as the host material for cathode sulfur.

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

[0026] (1) The method of in-situ etching to prepare MXene described in this invention can reduce environmental pollution and improve operational safety. Moreover, MXene@NiSe2 heterostructure materials can be prepared by a simple microwave method. The operation process is simple and easy to obtain, and it has good application prospects.

[0027] (2) The MXene@NiSe2 prepared in this invention exhibits a synergistic effect due to the coupling between its heterogeneous regions. The unique interface endows the material with unique electronic conductivity, strong adsorption, and catalytic activity for LiPSs. The heterogeneous structure can compensate for the low catalytic performance of single-component materials, thereby mitigating the shuttle effect in Li-S batteries.

[0028] (3) Adding NiSe2 nanoparticles to MXene materials to construct a three-dimensional porous structure can increase the specific surface area of ​​the material and physically restrict the passage of polysulfides. In addition, the contact interface between MXene and NiSe2 can further increase the number of catalytic and adsorption active sites, exerting a synergistic effect of catalytic conversion and chemisorption of polysulfides, thereby improving the performance and cycle life of Li-S batteries.

[0029] (4) The MXene@NiSe2 heterostructure sulfur host material prepared in this invention is used in lithium-sulfur batteries, and the initial charge-discharge specific capacity of the battery at 0.2C is 967.65-1212.39 mAh g. -1 After 100 charge-discharge cycles, it still maintains a capacity of 374.96–678.49 mAh g. -1 The capacity. Attached Figure Description

[0030] Figure 1 Scanning electron microscope (SEM) images of the prepared MXene@NiSe2 heterostructure material;

[0031] Figure 2 Transmission electron microscopy (TEM) images of the prepared MXene@NiSe2 heterostructure material;

[0032] Figure 3 Comparison of X-ray diffraction (XRD) results for the prepared MXene@NiSe2 heterostructure material;

[0033] Figure 4 The initial capacity diagram of the prepared MXene@NiSe2 heterostructure material used in Li-S cells at 0.2C is shown.

[0034] Figure 5 The charge-discharge cycle diagram of the prepared MXene@NiSe2 heterostructure material at 0.2C for use in Li-S batteries is shown. Detailed Implementation

[0035] 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.

[0036] Example 1

[0037] I. Preparation of MXene@NiSe2 heterostructure material, the steps are as follows:

[0038] (1) Preparation of MXene nanosheet colloidal solution: 20 mL of 9M hydrochloric acid and 1.5 g of lithium fluoride mixed solution were stirred for 20 min, then 1 g of MAX phase was slowly added and stirred continuously in a water bath for 48 h. After multiple centrifugations and ultrasonic exfoliation, a concentration of 5 mg / mL was obtained. -1 MXene nanosheet colloidal solution.

[0039] (2) Preparation of precursor powder: 100 mg of nickel hexahydrate and nickel nitrate, 30 mL of MXene nanosheet colloidal solution and 200 mg of selenium powder were thoroughly mixed and stirred for 4 h and then freeze-dried to form precursor powder.

[0040] (3) Put 200mg selenium powder, 50mg PAN (polyacrylonitrile), and 50mg MXene precursor powder into a mortar, mix them thoroughly and grind them evenly, and then place them in a small container with a lid.

[0041] (4) Place the small container with a lid from step (3) into the large container with a lid containing copper oxide powder; wherein, the copper oxide powder is used as a microwave absorbing material and the height of the powder must exceed the height of the sample in the small container with a lid.

[0042] (5) Place the entire system into a microwave reactor with a microwave power of 1000W, a heating time of 30min, and a temperature of 300℃ to obtain the sample.

[0043] II. Preparation of cathode material and electrode sheet, the steps are as follows:

[0044] (1) Using solid melting method to load sulfur, the sample obtained in step one (5) is mixed with sublimed sulfur powder at a mass ratio of 1:4, and heat-treated at 155°C for 2 hours in a tube furnace under nitrogen atmosphere to obtain cathode material;

[0045] (2) Preparation of electrode sheets: The cathode material, carbon black and binder obtained in step (1) are ground and mixed evenly in a mass ratio of 8:1:1. Then, NMP (N-methylpyrrolidone) solution is added and the mixture is continuously stirred magnetically for 12 hours. The evenly dispersed and viscous slurry is coated onto aluminum foil, vacuum dried at 60°C for 12 hours, and then cut into circular positive electrode sheets with a diameter of about 14 mm for later use.

[0046] III. Assemble the Li-S battery, the steps are as follows:

[0047] The positive electrode, lithium negative electrode and Celgard 2400 separator obtained in step 2 (2) were used to assemble a Li-S battery. The assembled battery was left to stand for 12 hours before electrochemical testing was performed.

[0048] Example 2

[0049] I. Preparation of MXene@NiSe2 heterostructure material, the steps are as follows:

[0050] (1) Preparation of MXene nanosheet colloidal solution: 40 mL of 9M hydrochloric acid and 3 g of lithium fluoride mixed solution were stirred for 20 min, then 2 g of MAX phase was slowly added and stirred in a water bath for 48 h. After multiple centrifugations and ultrasonic exfoliation, a concentration of 5 mg / mL was obtained. -1 MXene nanosheet colloidal solution.

[0051] (2) Preparation of precursor powder: 100 mg of nickel hexahydrate and nickel nitrate, 30 mL of MXene nanosheet colloidal solution and 200 mg of selenium powder were thoroughly mixed and stirred for 4 h and then freeze-dried to form precursor powder.

[0052] (3) Put 200mg selenium powder, 100mg PAN and 50mg MXene precursor powder into a mortar, mix them thoroughly and grind them evenly, and then put them into a small container with a lid.

[0053] (4) Place the small container with a lid from step (3) into the large container with a lid containing copper oxide powder; wherein, the copper oxide powder is used as a microwave absorbing material and the height of the powder must exceed the height of the sample in the small container with a lid.

[0054] (5) Place the entire system into a microwave reactor with a microwave power of 1000W, a heating time of 30min, and a temperature of 300℃ to obtain the sample.

[0055] II. Preparation of cathode material and electrode sheet, the steps are as follows: (1) Using solid melting method to load sulfur, the sample obtained in step one (5) is mixed with sublimed sulfur powder at a mass ratio of 1:4, and heat-treated at 155°C for 2 hours in a tube furnace under nitrogen atmosphere to obtain cathode material;

[0056] (2) Preparation of electrode sheet: The sample obtained in step (1), carbon black and binder are ground and mixed evenly in a mass ratio of 8:1:1. NMP solution is added and the mixture is continuously stirred magnetically for 12 hours. The evenly dispersed and viscous slurry is coated onto aluminum foil, vacuum dried at 60°C for 12 hours, and then cut into circular positive electrode sheets with a diameter of about 14 mm for later use.

[0057] III. Assemble the Li-S battery. The steps are as follows: Assemble the positive electrode, lithium negative electrode and Celgard2400 separator obtained in step 2 (2) into a Li-S battery. After the assembled battery is left to stand for 12 hours, perform electrochemical tests.

[0058] Example 3

[0059] I. Preparation of MXene@NiSe2 heterostructure material, the steps are as follows:

[0060] (1) Preparation of MXene nanosheet colloidal solution: 40 mL of 9M hydrochloric acid and 3 g of lithium fluoride mixed solution were stirred for 20 min, then 2 g of MAX phase was slowly added and stirred in a water bath for 48 h. After multiple centrifugations and ultrasonic exfoliation, a concentration of 5 mg / mL was obtained. -1 MXene nanosheet colloidal solution.

[0061] (2) Preparation of precursor powder: 100 mg of nickel hexahydrate and nickel nitrate, 30 mL of MXene nanosheet colloidal solution and 400 mg of selenium powder were thoroughly mixed and stirred for 4 h, and then freeze-dried to form precursor powder.

[0062] (3) Put 400mg selenium powder, 50mg PAN and 50mg MXene precursor powder into a mortar, mix them thoroughly and grind them evenly, and then put them into a small container with a lid.

[0063] (4) Place the small container with a lid from step (3) into the large container with a lid containing copper oxide powder; wherein, the copper oxide powder is used as a microwave absorbing material and the height of the powder must exceed the height of the sample in the small container with a lid.

[0064] (5) Place the entire system into a microwave reactor with a microwave power of 1000W, a heating time of 30min, and a temperature of 300℃ to obtain the sample.

[0065] II. Preparation of cathode material and electrode sheet, the steps are as follows:

[0066] (1) Using solid melting method to load sulfur, the sample obtained in step one (5) was mixed with sublimed sulfur powder at a mass ratio of 1:4, and heat-treated at 155°C for 2 hours in a tube furnace under nitrogen atmosphere to obtain cathode material;

[0067] (2) Preparation of electrode sheets: The sample obtained in step (1), carbon black and binder are ground and mixed evenly in a mass ratio of 8:1:1. NMP solvent is added and the mixture is continuously stirred magnetically for 12 hours. The evenly dispersed and viscous slurry is coated onto aluminum foil, vacuum dried at 60°C for 12 hours, and then cut into circular positive electrode sheets with a diameter of about 14 mm for later use.

[0068] III. Assemble the Li-S battery, the steps are as follows:

[0069] The positive electrode, lithium negative electrode and Celgard 2400 separator obtained in step 2 (2) were used to assemble a Li-S battery. The assembled battery was left to stand for 12 hours before electrochemical testing was performed.

[0070] Example 4

[0071] I. Preparation of MXene@NiSe2 heterostructure material, the steps are as follows: (1) Preparation of MXene nanosheet colloidal solution: 40 mL of 9M hydrochloric acid and 3 g of lithium fluoride mixed solution were stirred for 20 min, then 2 g of MAX phase was slowly added and stirred in a water bath for 48 h, and then the solution was obtained by ultrasonic exfoliation after multiple centrifugations to a concentration of 5 mg / mL. -1 MXene nanosheet colloidal solution.

[0072] (2) Preparation of precursor powder: 100mg of nickel hexahydrate and nickel nitrate, 30mL of MXene nanosheet colloidal solution and 200mg of selenium powder are thoroughly mixed and stirred for 4h and then freeze-dried to form precursor powder. (3) 200mg of selenium powder, 200mg of PAN and 50mg of MXene precursor powder are put into a mortar and thoroughly mixed and ground evenly, and then placed in a small container with a lid.

[0073] (4) Place the small container with a lid from step (3) into the large container with a lid containing copper oxide powder, wherein the copper oxide powder is used as a microwave absorbing material and the height of the powder must exceed the height of the sample in the small container with a lid.

[0074] (5) Place the entire system into a microwave reactor with a microwave power of 1000W, a heating time of 30min, and a temperature of 300℃ to obtain the sample.

[0075] II. Preparation of cathode material and electrode sheet, the steps are as follows:

[0076] (1) Using solid melting method to load sulfur, the sample obtained in step one (5) was mixed with sublimed sulfur powder at a mass ratio of 1:4, and heat-treated at 155°C for 2 hours in a tube furnace under nitrogen atmosphere to obtain cathode material;

[0077] (2) Preparation of electrode sheets: The sample obtained in step (1), carbon black and binder are ground and mixed evenly in a mass ratio of 8:1:1. NMP solvent is added and the mixture is continuously stirred magnetically for 12 hours. The evenly dispersed and viscous slurry is coated onto aluminum foil, vacuum dried at 60°C for 12 hours, and then cut into circular positive electrode sheets with a diameter of about 14 mm for later use.

[0078] III. Assemble the Li-S battery, the steps are as follows:

[0079] The positive electrode, lithium negative electrode and Celgard 2400 separator obtained in step 2 (2) were used to assemble a Li-S battery. The assembled battery was left to stand for 12 hours before electrochemical testing was performed.

[0080] Test results:

[0081] Figure 1 , Figure 2The structure of the MXene@NiSe2 heterostructure material is shown in the figure. As can be seen from the figure, the material has a three-dimensional porous MXene framework, and NiSe2 nanoparticles are uniformly distributed on the MXene framework.

[0082] Figure 3 The XRD pattern of the MXene@NiSe2 heterostructure material is shown, and it can be seen from the figure that the MXene@NiSe2 heterostructure was successfully prepared.

[0083] Figure 4 The initial capacity diagrams of the MXene@NiSe2 heterostructure materials prepared in Examples 1-4 for use in Li-S batteries at 0.2C are shown below:

[0084] The battery prepared in Example 1 exhibited a first-cycle discharge specific capacity as high as 1212.39 mAh g. -1 ;

[0085] The battery prepared in Example 2 exhibited a first-cycle discharge specific capacity as high as 1036.93 mAh g. -1 ;

[0086] The battery prepared in Example 3 exhibited a first-cycle discharge specific capacity as high as 1124.6 mAh g. -1 ;

[0087] The battery prepared in Example 4 exhibited a first-cycle discharge specific capacity as high as 967.65 mAh g. -1 .

[0088] Figure 5 The charge-discharge cycle diagrams of the MXene@NiSe2 heterostructure materials prepared in Examples 1-4 at 0.2C for use in Li-S batteries are shown below:

[0089] The battery prepared in Example 1 retained 678.49 mAh g after 100 charge-discharge cycles. -1 The capacity;

[0090] The battery prepared in Example 2 retained 562.07 mAh g after 100 charge-discharge cycles. -1 The capacity;

[0091] The battery prepared in Example 3 still maintained a capacity of 459.33 mAh g after 100 charge-discharge cycles. -1 The capacity;

[0092] The battery prepared in Example 4 retained 374.96 mAh g after 100 charge-discharge cycles. -1 The capacity.

[0093] 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 MXene@NiSe2 heterostructure material for use as the sulfur host material in lithium-sulfur batteries, characterized in that, Includes the following steps: (1) Preparation of MXene nanosheet colloidal solution; (2) Preparation of precursor powder: Nickel salt, selenium powder and MXene nanosheet colloidal solution are mixed evenly and dried to form precursor powder; (3) After mixing the selenium powder, polymer A and precursor powder, grind them and place them in a small container with a lid; the polymer A is polyacrylonitrile or polyvinylpyrrolidone; in step (3), the mass ratio of the selenium powder, polymer A and precursor powder is 200-1000mg: 50-250mg: 50-250mg. (4) Place the small container with a lid into a large container with a lid containing microwave-absorbing material copper oxide, and carry out a microwave reaction to obtain the product.

2. The method for preparing the MXene@NiSe2 heterostructure material for the sulfur host material of lithium-sulfur batteries according to claim 1, characterized in that, In step (1), the steps for preparing the MXene nanosheet colloidal solution are as follows: lithium fluoride is added to hydrochloric acid and mixed, MAX phase is added, and the solution is obtained after subsequent processing.

3. The method for preparing the MXene@NiSe2 heterostructure material for the sulfur host material of lithium-sulfur batteries according to claim 2, characterized in that, The MAX phase is one of Ti3AlC2, Nb2AlC and V2AlC, and the corresponding MXene is one of Ti3C2, Nb2C and V2C.

4. The method for preparing the MXene@NiSe2 heterostructure material for the sulfur host material of lithium-sulfur batteries according to claim 2, characterized in that, In step (1), the mass ratio of lithium fluoride to the MAX phase is 1.5-3g:1-2g.

5. The method for preparing the MXene@NiSe2 heterostructure material for the sulfur host material of lithium-sulfur batteries according to claim 1, characterized in that, In step (2), the nickel salt is selected from nickel chloride, nickel nitrate, and nickel sulfate; the mass ratio of nickel salt, selenium powder, and MXene nanosheet colloidal solution is 100-500 mg: 200-1000 mg: 100-500 mg; and the concentration of the MXene nanosheet colloidal solution is 5-20 mg / mL.

6. The method for preparing the MXene@NiSe2 heterostructure material for the sulfur host material of lithium-sulfur batteries according to claim 1, characterized in that, In step (4), the microwave power is 500-1000 W and the microwave heating time is 20-40 min.

7. An MXene@NiSe2 heterostructure material for use as the sulfur host material in lithium-sulfur batteries, characterized in that: Prepared using the method described in any one of claims 1 to 6.

8. A cathode material, characterized in that: The MXene@NiSe2 heterostructure material of claim 7 was obtained by loading sulfur via solid-state melting.

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