A bismuth-containing nickel bimetallic selenide composite material, a preparation method and application thereof

Abstract

The application relates to the technical field of sodium ion battery electrode materials, in particular to a composite material containing bismuth-nickel bimetallic selenide and a preparation method and application thereof. The preparation method is as follows: taking a rod-shaped copper nickel diketone precursor with unstable structure as a nickel source under high-temperature pyrolysis, carrying out a hydrothermal reaction on the nickel source with a bismuth source, and then carrying out selenization treatment on the bismuth source and selenium in an inert atmosphere through a gas phase deposition mode, so that the bismuth-nickel bimetallic selenide composite material with two-dimensional nano-plate loaded nano-particles can be obtained after being cooled to room temperature. The method fully utilizes the low thermal stability of nickel diketone oxime, realizes the conversion of the rod-shaped-porous-small nano-particles in the pyrolysis-selenization process, and is favorable for the final uniform wrapping on the surface of the bismuth selenide nano-plate. The raw materials used in the method are cheap and rich in sources, the production cycle is short, and the stability is good. Meanwhile, the complementarity of the working potentials of the two components in the sodium storage process can also realize the efficient sodium storage in the whole voltage range.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery electrode materials technology, specifically a composite material containing bismuth-nickel bimetallic selenide, its preparation method, and its application. Background Technology

[0002] As a potential complement to lithium-ion batteries, sodium-ion batteries (SIBs) remain limited in their applications due to slow kinetics and significant volume expansion during repeated charge-discharge cycles. Notably, the preparation of high-performance anode materials is crucial for the further application of SIBs. Existing research indicates that alloy-type anodes can provide high theoretical capacity and low operating voltage, but drastic volume changes lead to rapid capacity decay. For conversion-type anodes, their excellent specific capacity stems from a multi-electron transfer mechanism, but poor conductivity and slow reaction kinetics reduce the electrochemical activity and energy density of the entire cell. Therefore, developing composite anodes with fast kinetics, high conductivity, and excellent electrochemical activity is of great significance for advancing the further development of SIBs.

[0003] Conversion-alloying anodes with a dual sodium storage mechanism achieve high specific capacity and low operating potential. This superior performance is mainly attributed to the reversible conversion reaction and metal alloying process during cycling. In particular, the formed conversion products provide a buffer space to accommodate significant volume changes, while reducing internal stress during alloying / dealloying, thereby achieving structural stability of the electrode material. As a typical anode with a conversion-alloying reaction mechanism, bismuth selenide (Bi2Se3) exhibits an excellent theoretical capacity (1064 mAh g⁻¹). -1Bi₂Se₃ possesses a large interlayer distance. Furthermore, it is a topological insulator with surface conductive states, effectively mitigating the deficiency of insufficient internal conductivity. However, its significant volume expansion, low intrinsic conductivity, and slow reaction kinetics hinder the release of theoretical performance. Existing technologies have proposed a series of methods to address these issues, such as nanocrystallization of active particles, nanostructure design, and coupling with a carbon matrix. Admittedly, these strategies still have limitations. Nanostructuring of active materials is accompanied by a decrease in bulk density, while structural design and carbon modification will reduce the proportion of active centers. Heterogeneous structure engineering, constructed from two or more active species with different Fermi levels, is considered the most effective strategy for improving anode performance. Significant improvements in electrochemical performance and conductivity depend primarily on Fermi level mismatch, which induces spontaneous charge transfer and optimizes reaction kinetics. Simultaneously, abundant phase interfaces and strong boundary effects can provide more active sites and accelerate ion diffusion. However, many reported studies on the construction of Bi2Se3 heterojunctions have not focused on utilizing the complementary reaction potentials between Bi2Se3 and another component to achieve sodium storage over a wide voltage range and thus improve the overall sodium storage capacity. Therefore, how to utilize the complementary reaction potentials between other components and Bi2Se3 to rationally design and prepare highly active Bi2Se3-based heterojunction anode materials is of great significance for improving the sodium storage performance of Bi2Se3 and for the design and development of novel heterojunction anode materials. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide a bismuth-nickel bimetallic selenide composite material, its preparation method, and its applications. This composite material simultaneously contains Bi₂Se₃ and NiSe₂ components, which exhibit significant complementarity in the sodium storage reaction potential, enabling efficient sodium storage over a wide voltage range. Furthermore, the heterogeneous interface formed by the Bi₂Se₃ and NiSe₂ components and the precursor-derived carbon layer not only facilitate rapid charge transfer, providing more sodium storage sites and enhancing capacity, but also, through the confinement effect of the carbon layer, effectively suppresses volume expansion during the sodium insertion / extraction process.

[0005] To achieve the above objectives, this invention discloses a method for preparing a composite material containing bismuth-nickel bimetallic selenide, specifically comprising the following steps:

[0006] (1) Ni(CH3COO)2•4H2O was dissolved in water to prepare solution A, and dimethylglyoxime was dissolved in anhydrous ethanol to prepare solution B. After mixing solutions A and B, the mixture was stirred in a constant temperature water bath for a certain period of time and then allowed to stand for further reaction. After the reaction was completed, the resulting mixed solution was centrifuged and the supernatant was discarded to obtain the lower precipitate. The precipitate was washed by centrifugation with anhydrous ethanol several times and then dried under vacuum to obtain the nickel dimethylglyoxime precursor, denoted as DNi.

[0007] (2) The prepared nickel dimethylglyoxime precursor was heated to a certain temperature in an inert atmosphere, and then kept at a constant temperature. After the constant temperature was completed, it was naturally cooled to room temperature to obtain Ni@C.

[0008] (3) A certain amount of Ni@C was added to the ethanol solution of Bi(NO3)3•5H2O. The mixture was stirred in a constant temperature water bath, then KI was added and stirred for a certain time. After stirring, the resulting mixed solution was transferred to a reaction vessel for hydrothermal reaction. After the reaction, the resulting mixed solution was centrifuged and the supernatant was discarded to obtain the lower precipitate. The precipitate was washed by centrifugation with anhydrous ethanol several times and then dried under vacuum. The obtained sample was named BiOI / Ni@C precursor.

[0009] (4) The BiOI / Ni@C precursor prepared in step (3) is mixed with selenium powder and then ground. After grinding, the mixture is heated in stages under an inert atmosphere for selenization treatment. After natural cooling and cooling to room temperature, a composite material containing bismuth-nickel bimetallic selenide is obtained.

[0010] Furthermore, in step (1), the mass concentration of Ni(CH3COO)2•4H2O in solution A is 10~15 mg / mL, the mass concentration of dimethylglyoxime in solution B is 4~8 mg / mL, and the volume ratio of solution A to solution B is 2:1~1:3.

[0011] Furthermore, in step (1), the temperature of the constant temperature water bath is 25~45℃, the stirring reaction time is 1~3 hours, the standing reaction time is 4~9 hours, the centrifugation speed is 5000~10000 rpm, and the centrifugation time is 5~15 minutes; the vacuum drying temperature is 50~80℃.

[0012] Furthermore, in step (2), the inert atmosphere is N2 atmosphere, the heating rate is 1~3℃ / min, the temperature is raised to 400~800℃, and the holding time is 3~7 hours.

[0013] Furthermore, in step (3), the ethanol solution of Bi(NO3)3•5H2O is obtained by dissolving Bi(NO3)3•5H2O in anhydrous ethanol.

[0014] Furthermore, in step (3), the mass of Ni@C is 0~300mg, the mass concentration of bismuth nitrate is 1~3mg / mL, and the molar ratio of Bi(NO3)3•5H2O to KI is 1:0.5~1:2.

[0015] Furthermore, in step (3), the temperature of the constant temperature water bath is 25℃, the stirring reaction time is 0.5~2 hours, after adding KI, stirring is continued for 1~3 hours, the temperature of the hydrothermal reaction is 90~120℃, the hydrothermal reaction time is 5~8 hours, the centrifugation speed is 5000~10000 rpm, the centrifugation time is 5~15 minutes; the vacuum drying temperature is 50~80℃.

[0016] Furthermore, in step (4), the mass ratio of BiOI / Ni@C precursor to selenium powder is 1:1 to 1:3, the grinding time is 5 to 20 minutes, the inert atmosphere is N2 atmosphere, and the stage heating process is as follows: first heat to 200 to 500℃ at a heating rate of 1 to 5℃ / min, then perform the first isothermal test for 2 to 5 hours, after which heat to 500 to 800℃ at a heating rate of 1 to 5℃ / min, and perform the second isothermal test for 1 to 4 hours.

[0017] The present invention also aims to provide a composite material containing bismuth-nickel bimetallic selenide obtained by the above method and the application of the composite material containing bismuth-nickel bimetallic selenide as a negative electrode material for sodium-ion batteries.

[0018] This invention uses rod-shaped nickel dimethylglyoxime, structurally unstable under high-temperature pyrolysis, as the nickel source. After a hydrothermal reaction with a bismuth source, it undergoes selenization treatment with selenium via vapor deposition in an inert atmosphere. Upon cooling to room temperature, a bismuth-nickel bimetallic selenide composite material with two-dimensional nanoplatelets loaded with nanoparticles is obtained. This method fully utilizes the low thermal stability of nickel dimethylglyoxime, achieving a transformation from rod-shaped to porous to small nanoparticles during the pyrolysis-selenization process. This morphological transformation facilitates the uniform coating of the bismuth selenide nanoplatelets onto the surface. The raw materials used in this method are inexpensive and abundant, with a short production cycle and good stability. Furthermore, the complementary working potentials of the two components during sodium storage enable efficient sodium storage across the entire voltage range. The resulting composite material possesses a unique heterostructure. The resulting built-in electric field not only accelerates charge transport and enhances the overall conductivity of the material, thereby improving rate performance and cycle stability, but also provides more sodium adsorption sites at the heterojunction, achieving high sodium storage capacity output.

[0019] This invention successfully prepared a two-dimensional Bi₂Se₃ / NiSe₂@C composite material with multiple sodium storage mechanisms via a hydrothermal combined one-step selenization method. The two-dimensional nanoplates with uniformly coated nanoparticles possess a unique hierarchical structure, which facilitates the exposure of more active sites and enhances the structural stability of the electrode material. Furthermore, the introduction of the NiSe₂ phase allows coupling with Bi₂Se₃ to form a heterostructure, thereby inducing a strong electric field effect, generating abundant heterointerfaces, improving the material's conductivity, and accelerating reaction kinetics. More importantly, the NiSe₂ component and Bi₂Se₃ have different reaction voltages, which can compensate for the low utilization rate of Bi₂Se₃ within the voltage window and provide abundant active sites, thus significantly improving the sodium storage capacity.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) The preparation method proposed in this invention takes advantage of the fact that the nickel precursor of dimethylglyoxime can provide both nickel and carbon sources at the same time. The target product is obtained in just three steps: pyrolysis of the precursor, hydrothermal composite and mixed selenization. The material obtained has high yield, good stability and strong reproducibility, providing a choice for exploring the large-scale synthesis of high-rate sodium-ion battery anode materials with excellent performance.

[0022] (2) This invention only uses a simple hydrothermal combined gas phase selenization method. The process is simple and easy to implement, has low equipment requirements, short production cycle, and great application potential.

[0023] (3) The composite material containing bismuth-nickel bimetallic selenide obtained by the preparation method of the present invention has a unique hierarchical structure of two-dimensional loaded nanoparticles, which shortens the electron diffusion distance and increases the conductivity and structural stability of the material. At the same time, this two-dimensional structure can expose more active sites and increase the sodium storage capacity. The constructed heterostructure can generate an internal electric field to further accelerate the transfer of charge at the interface and the migration speed of sodium ions, thereby effectively improving the material reaction kinetics.

[0024] (4) When the bismuth-nickel bimetallic selenide composite material prepared by the method of this invention is used as the negative electrode material of sodium-ion batteries, the initial discharge specific capacity can reach as high as 632.62 mAh / g and 673.22 mAh / g, respectively, when tested at current densities of 0.5 A / g and 1 A / g. After 600 and 800 cycles, the discharge specific capacity can be maintained at 399.79 mAh / g and 430.17 mAh / g, respectively, showing excellent long-cycle performance. Even when assembled into a full cell, after 3581 cycles at a current density of 1 A / g, the discharge specific capacity can still reach 133.49 mAh / g, showing good long-life performance. In the rate performance test at different current densities, the prepared bismuth-nickel bimetallic selenide composite material still shows good capacity retention. The aforementioned test results show that this bismuth-nickel bimetallic selenide composite material not only has high sodium storage performance, but also has excellent rate performance, making it a potential application material for high-energy-density and high-power-density sodium-ion batteries.

[0025] (5) The present invention combines hydrothermal and gas-phase selenization strategies to construct a composite material containing bismuth-nickel bimetallic selenide, making full use of the advantages of different reaction voltages of NiSe2 component and Bi2Se3, effectively compensating for the low utilization rate of Bi2Se3 in the voltage window, providing additional active sites, thereby achieving high capacity output over a wide voltage range. Attached Figure Description

[0026] Figure 1 The images are SEM images of DNi prepared in step (1) of Example 2, Ni@C prepared in step (2), and NiSe2@C prepared in Comparative Example 1. The images marked in the upper left corner as (a) and (b) are SEM images of DNi; (c) and (d) are SEM images of Ni@C at different magnifications; and (e) and (f) are SEM images of NiSe2@C at different magnifications.

[0027] Figure 2 SEM images of BiOI prepared in step (1) and Bi2SeO2 / Bi3Se4 prepared in step (2) are shown in Comparative Example 2. The images marked (a) and (b) in the upper left corner are SEM images of BiOI at different magnifications; (c) and (d) are SEM images of Bi2SeO2 / Bi3Se4 at different magnifications.

[0028] Figure 3 The XRD patterns of Ni@C prepared in step (2) and BiOI / Ni@C-2# precursor prepared in step (3) of Example 2 are shown.

[0029] Figure 4The images shown are SEM, TEM, and HR-TEM images of Bi2Se3 / NiSe2@C-2# prepared in Example 2. The images marked in the upper left corner (a) and (b) are SEM images at different magnifications; (c) is a TEM image; and (d), (e), and (f) are HR-TEM images.

[0030] Figure 5 The XRD patterns of Bi2Se3 / NiSe2@C-2# prepared in Example 2, NiSe2@C prepared in Comparative Example 1, and Bi2SeO2 / Bi3Se4 prepared in Comparative Example 2 are shown.

[0031] Figure 6 The BET plot of Bi2Se3 / NiSe2@C-2# prepared in Example 2;

[0032] Figure 7 EIS images of sodium-ion batteries prepared in Example 2 (Bi2Se3 / NiSe2@C-2#), Comparative Example 1 (NiSe2@C), and Comparative Example 2 (Bi2SeO2 / Bi3Se4) as negative electrodes after 5 cycles at a current density of 1 A / g.

[0033] Figure 8 The cycling performance curves of sodium-ion batteries prepared in Example 2 (Bi2Se3 / NiSe2@C-2#), Comparative Example 1 (NiSe2@C), and Comparative Example 2 (Bi2SeO2 / Bi3Se4) as negative electrodes are shown at a current density of 0.5 A / g.

[0034] Figure 9 The cycling performance curves of sodium-ion batteries with Bi2Se3 / NiSe2@C-2# prepared in Example 2, NiSe2@C prepared in Comparative Example 1, and Bi2SeO2 / Bi3Se4 prepared in Comparative Example 2 as negative electrodes are shown at a current density of 1 A / g.

[0035] Figure 10 The cycling performance curves of sodium-ion batteries prepared in Example 1 and Example 3, respectively, as negative electrodes, are shown at a current density of 1 A / g.

[0036] Figure 11 The rate performance curves of sodium-ion batteries with Bi2Se3 / NiSe2@C-2# prepared in Example 2, NiSe2@C prepared in Comparative Example 1, and Bi2SeO2 / Bi3Se4 prepared in Comparative Example 2 as negative electrodes are shown.

[0037] Figure 12The cycling performance curve of the sodium-ion full cell prepared in Example 2 with Bi2Se3 / NiSe2@C-2# as the negative electrode at a current density of 1A / g is shown. Detailed Implementation

[0038] To better understand the content of this invention, it will be further described below with reference to specific embodiments and accompanying drawings. The following embodiments are based on the technology of this invention and provide detailed implementation methods and operating steps, but the scope of protection of this invention is not limited to the following embodiments.

[0039] Example 1:

[0040] (1) Dissolve 3.75g of Ni(CH3COO)2•4H2O in 300mL of water to prepare solution A, and dissolve 1.74g of dimethylglyoxime in 300mL of anhydrous ethanol to prepare solution B; pour solution A into solution B, and stir the reaction for 2 hours under constant temperature water bath at 30℃, and then let it stand for 6 hours; after the reaction is completed, centrifuge the resulting mixed solution at 8000 rpm for 10 minutes, discard the supernatant, and obtain the lower precipitate. Wash the precipitate three times with anhydrous ethanol by centrifugation, and then vacuum dry it at 60℃ for 12 hours. The resulting red powder is the nickel dimethylglyoxime precursor, denoted as DNi;

[0041] (2) The prepared DNi was heated to 600℃ in N2 atmosphere at a heating rate of 2℃ / min and kept at the temperature for 5 hours. After natural cooling to room temperature, the resulting sample was denoted as Ni@C.

[0042] (3) Dissolve 125 mg of Bi(NO3)3•5H2O in 60 mL of anhydrous ethanol. After complete dissolution, add 50 mg of Ni@C prepared in step (2). Then, stir for 1 hour in a constant temperature water bath at 25 °C. Then, add 42.4 mg of KI and continue stirring for 2 hours. After stirring, transfer the resulting mixed solution to a reaction vessel and hydrothermally react at 110 °C for 6 hours. After the reaction, centrifuge the resulting mixed solution at 8000 rpm for 10 minutes, discard the supernatant, and obtain the lower precipitate. Wash the precipitate three times with anhydrous ethanol by centrifugation, and then vacuum dry at 60 °C for 24 hours. The dried sample is named BiOI / Ni@C-1# precursor.

[0043] (4) The obtained BiOI / Ni@C-1# precursor and selenium powder were mixed and ground for 10 minutes at a mass ratio of 1:2. Then, the mixture was subjected to stage heating under N2 atmosphere to perform selenization treatment. The stage heating process was as follows: heating to 400℃ at a heating rate of 2℃ / min and holding at 400℃ for 4 hours, then heating to 600℃ at a heating rate of 2℃ / min and holding at 600℃ for 2 hours, and then naturally cooling to room temperature. Finally, a composite material containing bismuth-nickel bimetallic selenide was obtained, denoted as Bi2Se3 / NiSe2@C-1#.

[0044] Example 2:

[0045] (1) Dissolve 3.75g of Ni(CH3COO)2•4H2O in 300mL of water to prepare solution A, and dissolve 1.74g of dimethylglyoxime in 300mL of anhydrous ethanol to prepare solution B; pour solution A into solution B, and stir the reaction for 2 hours under constant temperature water bath at 30℃, and then let it stand for 6 hours; after the reaction is completed, centrifuge the resulting mixed solution at 8000 rpm for 10 minutes, discard the supernatant, and obtain the lower precipitate. Wash the precipitate three times with anhydrous ethanol by centrifugation, and then vacuum dry it at 60℃ for 12 hours. The resulting red powder is the nickel dimethylglyoxime precursor, denoted as DNi;

[0046] (2) The prepared DNi was heated to 600℃ in N2 atmosphere at a heating rate of 2℃ / min and kept at the temperature for 5 hours. After natural cooling to room temperature, the resulting sample was denoted as Ni@C.

[0047] (3) Dissolve 125 mg of Bi(NO3)3•5H2O in 60 mL of anhydrous ethanol. After complete dissolution, add 100 mg of Ni@C prepared in step (2). Then, stir for 1 hour in a constant temperature water bath at 25 °C. Then, add 42.4 mg of KI and continue stirring for 2 hours. After stirring, transfer the resulting mixed solution to a reaction vessel and hydrothermally react at 110 °C for 6 hours. After the reaction, centrifuge the resulting mixed solution at 8000 rpm for 10 minutes, discard the supernatant, and obtain the lower precipitate. Wash the precipitate three times with anhydrous ethanol by centrifugation and then vacuum dry at 60 °C for 24 hours. The dried sample is named BiOI / Ni@C-2# precursor.

[0048] (4) The obtained BiOI / Ni@C-2# precursor and selenium powder were mixed and ground for 10 minutes at a mass ratio of 1:2. Then, the mixture was subjected to stage heating under N2 atmosphere to perform selenization treatment. The stage heating process was as follows: heating to 400℃ at a heating rate of 2℃ / min and holding at 400℃ for 4 hours, then heating to 600℃ at a heating rate of 2℃ / min and holding at 600℃ for 2 hours, and then naturally cooling to room temperature. Finally, a composite material containing bismuth-nickel bimetallic selenide was obtained, denoted as Bi2Se3 / NiSe2@C-2#.

[0049] Example 3:

[0050] (1) Dissolve 3.75g of Ni(CH3COO)2•4H2O in 300mL of water to prepare solution A, and dissolve 1.74g of dimethylglyoxime in 300mL of anhydrous ethanol to prepare solution B; pour solution A into solution B, and stir the reaction for 2 hours under constant temperature water bath at 30℃, and then let it stand for 6 hours; after the reaction is completed, centrifuge the resulting mixed solution at 8000 rpm for 10 minutes, discard the supernatant, and obtain the lower precipitate. Wash the precipitate three times with anhydrous ethanol by centrifugation, and then vacuum dry it at 60℃ for 12 hours. The resulting red powder is the nickel dimethylglyoxime precursor, denoted as DNi;

[0051] (2) The prepared DNi was heated to 600℃ in N2 atmosphere at a heating rate of 2℃ / min and kept at the temperature for 5 hours. After natural cooling to room temperature, the resulting sample was denoted as Ni@C.

[0052] (3) Dissolve 125 mg of Bi(NO3)3•5H2O in 60 mL of anhydrous ethanol. After complete dissolution, add 200 mg of Ni@C prepared in step (2). Then, stir for 1 hour in a constant temperature water bath at 25 °C. Then, add 42.4 mg of KI and continue stirring for 2 hours. After stirring, transfer the resulting mixed solution to a reaction vessel and hydrothermally react at 110 °C for 6 hours. After the reaction, centrifuge the resulting mixed solution at 8000 rpm for 10 minutes, discard the supernatant, and obtain the lower precipitate. Wash the precipitate three times with anhydrous ethanol by centrifugation and then vacuum dry at 60 °C for 24 hours. The dried sample is named BiOI / Ni@C-3# precursor.

[0053] (4) The obtained BiOI / Ni@C-3# precursor and selenium powder were mixed and ground for 10 minutes at a mass ratio of 1:2. Then, the mixture was subjected to stage heating under N2 atmosphere to perform selenization treatment. The stage heating process was as follows: heating to 400℃ at a heating rate of 2℃ / min and holding at 400℃ for 4 hours, then heating to 600℃ at a heating rate of 2℃ / min and holding at 600℃ for 2 hours, and then naturally cooling to room temperature. Finally, a composite material containing bismuth-nickel bimetallic selenide was obtained, denoted as Bi2Se3 / NiSe2@C-3#.

[0054] Comparative Example 1:

[0055] (1) Dissolve 3.75g of Ni(CH3COO)2•4H2O in 300mL of water to prepare solution A, and dissolve 1.74g of dimethylglyoxime in 300mL of anhydrous ethanol to prepare solution B; pour solution A into solution B, and stir the reaction for 2 hours under constant temperature water bath at 30℃, and then let it stand for 6 hours; after the reaction is completed, centrifuge the resulting mixed solution at 8000 rpm for 10 minutes, discard the supernatant, and obtain the lower precipitate. Wash the precipitate three times with anhydrous ethanol by centrifugation, and then vacuum dry it at 60℃ for 12 hours. The resulting red powder is the nickel dimethylglyoxime precursor, denoted as DNi;

[0056] (2) The prepared DNi was heated to 600℃ in N2 atmosphere at a heating rate of 2℃ / min and kept at the temperature for 5 hours. After natural cooling to room temperature, the resulting sample was denoted as Ni@C.

[0057] (3) The Ni@C obtained in step (2) is mixed with selenium powder at a mass ratio of 1:2 and ground for 10 minutes. Then, it is subjected to stage heating under N2 atmosphere to perform selenization treatment. The stage heating process is as follows: heating to 400°C at a heating rate of 2°C / min and holding at 400°C for 4 hours, then heating to 600°C at a heating rate of 2°C / min and holding at 600°C for 2 hours, and then naturally cooling to room temperature; the resulting composite material is denoted as NiSe2@C.

[0058] Comparative Example 2:

[0059] (1) Dissolve 125 mg of Bi(NO3)3•5H2O in 60 mL of anhydrous ethanol. After complete dissolution, stir for 1 hour in a constant temperature water bath at 25 °C. Then add 42.4 mg of KI and continue stirring for 2 hours. After stirring, transfer the resulting mixed solution to a reaction vessel and hydrothermally react at 110 °C for 6 hours. After the reaction, centrifuge the resulting mixed solution at 8000 rpm for 10 minutes, discard the supernatant, and obtain the lower precipitate. Wash the precipitate three times with anhydrous ethanol by centrifugation, and then vacuum dry at 60 °C for 24 hours. The dried sample is named BiOI.

[0060] (2) The obtained BiOI and selenium powder were mixed and ground at a mass ratio of 1:2 for 10 minutes. Then, the mixture was subjected to stage heating under N2 atmosphere to achieve selenization treatment. The stage heating process was as follows: heating to 400℃ at a heating rate of 2℃ / min and holding at 400℃ for 4 hours, then heating to 600℃ at a heating rate of 2℃ / min and holding at 600℃ for 2 hours, and then naturally cooling to room temperature. The resulting composite material was denoted as Bi2SeO2 / Bi3Se4.

[0061] SEM analysis was performed using a ZEISS Gemini SEM 300 from Zeiss GmbH, Germany. A small amount of powdered sample was coated onto a black conductive adhesive and then sputter-coated with gold. SEM was used to characterize the surface morphology and particle size of the sample.

[0062] Figure 1 Figures (a) and (b) are SEM images of the nickel dimethylglyoxime precursor (DNi) prepared in step (1) of Example 2. The analysis shows that the prepared precursor is a smooth nanorod structure. Figure 1 Figures (c) and (d) are SEM images of Ni@C prepared in step (2) of Example 2. It can be seen from the figures that after the precursor is pyrolyzed at high temperature in an inert atmosphere, the rod-shaped structure will collapse and reassemble into a porous structure. Figure 1 Figures (e) and (f) in the middle are SEM images of NiSe2@C prepared in Comparative Example 1. It can be seen from the figures that after selenization treatment by vapor deposition, the porous structure is transformed in situ into an aggregated nanoparticle morphology.

[0063] Figure 2 Figures (a) and (b) are SEM images of BiOI prepared in step (1) of Comparative Example 2. The images show that the BiOI prepared by the hydrothermal reaction exhibits a regular two-dimensional nanoplate structure. After further selenization treatment, the resulting Bi2SeO2 / Bi3Se4 still maintains its two-dimensional structure, as shown in the figures. Figure 2 As shown in Figures (c) and (d), the retention of this two-dimensional structure indicates that the material has good structural stability.

[0064] To further confirm the successful preparation of the BiOI / Ni@C-2# precursor prepared by the hydrothermal reaction in steps (2) and (3) of Example 2, XRD tests were performed using a D / max-γβ type X-ray diffractometer manufactured by Rigaku Electric Co., Ltd. of Japan to analyze the phase composition of the sample.

[0065] Figure 3The XRD patterns of the Ni@C prepared in step (2) and the BiOI / Ni@C-2# precursor prepared in step (3) of Example 2 are shown. The figure shows that the Ni@C formed after the pyrolysis of the DNi precursor has three strong diffraction peaks, which are in good agreement with standard metallic Ni (PDF#70-1849). This result confirms that Ni in the Ni@C material exists in the form of metallic nickel. Furthermore, a broad, weak diffraction peak can be observed at an angle of approximately 25° in the curve, which can be attributed to the carbon material formed after the pyrolysis of the ligands in the DNi precursor. For BiOI / Ni@C-2#, the XRD curve includes the characteristic peaks of Ni@C, and also shows the main diffraction peaks of BiOI. The peaks of the BiOI component are in agreement with the standard peaks (PDF#73-2062). The XRD results fully confirm that Ni@C and BiOI / Ni@C-2# in Example 2 were successfully synthesized.

[0066] Figure 4 Figures (a) and (b) are SEM images of the Bi2Se3 / NiSe2@C-2# prepared in Example 2. The images show that the material consists of two-dimensional nanoplates uniformly encapsulated by nanoparticles. The plate-like structure originates from the Bi2Se3 component, while the nanoparticles are derived from the NiSe2 component. This unique hierarchical structure facilitates the exposure of active sites, allowing for the full utilization of the electrocatalytic activity of the active species. Simultaneously, this structure also promotes electron transfer, thereby enhancing the rate performance of the composite material.

[0067] Furthermore, a JEM-2100F field emission transmission electron microscope manufactured in Japan was used to analyze the microstructure and lattice fringes of the material, thereby determining its composition. Figure 4 Figure (c) is a TEM image of Bi2Se3 / NiSe2@C-2# prepared in Example 2. It can be seen from the figure that the formed two-dimensional nanoplate is a solid structure.

[0068] To further confirm the presence of NiSe2 and Bi2Se3 components and the formation of heterostructures, high-magnification TEM images were obtained, such as... Figure 4 In the middle figures (d), (e), and (f), the lattice fringe spacing of 0.315 nm / 0.311 nm corresponds to the (009) crystal plane of the Bi₂Se₃ phase, and the lattice fringe spacing of 0.351 nm corresponds to the (101) crystal plane of the Bi₂Se₃ phase. Figure 4 In (e), a significant difference in lattice fringes can be observed between Bi2Se3 and NiSe2, and the marked lattice fringes of 0.202 nm and 0.180 nm can be attributed to the (113) crystal plane of Bi2Se3 and the (311) crystal plane of NiSe2, respectively. Figure 4(f) The interplanar spacings of 0.242 nm and 0.215 nm can be attributed to the (211) and (220) crystal planes of NiSe2, respectively. The interplanar spacings of 0.256 nm, 0.270 nm, and 0.189 nm can be attributed to the (018), (107), and (116) crystal planes of Bi2Se3, respectively. The obvious differences in the lattice fringes in the material originate from the heterogeneous interface formed by the two phases of Bi2Se3 and NiSe2, indicating the successful preparation of the heterostructure. The presence of the heterostructure allows for the redistribution of charge at the interface, creating an internal electric field that increases the conductivity of the material, which is beneficial for the rapid transfer of electrons. Furthermore, the interface contains abundant defects and active sites that can further enhance the sodium storage capacity of the material.

[0069] Figure 5 The XRD patterns of Bi2Se3 / NiSe2@C-2# prepared in Example 2, NiSe2@C prepared in Comparative Example 1, and Bi2SeO2 / Bi3Se4 prepared in Comparative Example 2 are shown. The figures show that the NiSe2@C prepared in Comparative Example 1 corresponds one-to-one with the diffraction peaks of standard NiSe2 (PDF#97-064-6510). The Bi2SeO2 / Bi3Se4 prepared in Comparative Example 2 contains diffraction peaks of both the Bi2SeO2 phase (PDF#97-000-2903) and the Bi3Se4 phase. For the Bi2Se3 / NiSe2@C-2# prepared in Example 2, the curve shows diffraction peaks of both the Bi2Se3 phase (PDF#97-016-5226) and the NiSe2 phase (PDF#97-064-6510), clearly indicating the presence of these two components in the material, which is consistent with the high-magnification TEM results.

[0070] The specific surface area of ​​the composite material was analyzed by BET testing using an ASAP 2460 specific surface area and porosity analyzer manufactured by Micron Instruments, Inc. Figure 6 The image shows the nitrogen adsorption-desorption curves of the Bi2Se3 / NiSe2@C-2# composite material prepared in Example 2. The calculated specific surface area of ​​this composite material is 69.92 m². 2 / g, the large specific surface area of ​​the material can not only increase the wettability between the material and the electrolyte, but also help to expose more sodium storage active sites and enhance the sodium storage capacity of the electrode material.

[0071] The Bi2Se3 / NiSe2@C-1# prepared in Example 1, the Bi2Se3 / NiSe2@C-2# prepared in Example 2, the Bi2Se3 / NiSe2@C-3# prepared in Example 3, the NiSe2@C prepared in Comparative Example 1, and the Bi2SeO2 / Bi3Se4 composite material prepared in Comparative Example 2 were ground into powder and used as negative electrode active materials respectively. The battery performance of the sodium-ion battery negative electrode was measured using CR2032 coin-type battery test material.

[0072] First, the working electrode was prepared by mixing 70 wt% of Bi2Se3 / NiSe2@C-2# powder prepared in Example 2, 10 wt% of polymer binder (PVDF), and 20 wt% of conductive material (Super-P). The resulting slurry was then coated onto copper foil and dried at 80°C for 12 hours. The battery was assembled in a glove box using a Cellgard 2300 separator, a sodium metal sheet as the counter electrode, and DEGDME (diethylene glycol dimethyl ether) containing 1 M NaPF6 as the electrolyte. The battery was tested on a LANHE battery testing system (CT2001A, Wuhan, China) within a voltage window of 0.01-3 V (relative to Na). + Battery charging / discharging tests were performed using / Na. Electrochemical impedance spectroscopy (EIS) was conducted using a Shanghai Chenhua CHI660E electrochemical workstation. The test voltage was the open-circuit voltage, and the frequency was 0.01-10 Hz. 5 Hz.

[0073] The Bi2Se3 / NiSe2@C-2# powder prepared in Example 2 was replaced with the Bi2Se3 / NiSe2@C-1# powder prepared in Example 1, the Bi2Se3 / NiSe2@C-3# powder prepared in Example 3, the NiSe2@C powder prepared in Comparative Example 1, and the Bi2SeO2 / Bi3Se4 powder prepared in Comparative Example 2, respectively. The rest of the preparation of the working electrode and the testing process were the same as described above.

[0074] Figure 7Impedance plots are shown for the composite materials Bi2Se3 / NiSe2@C-2# (Prepared in Example 2), NiSe2@C (Prepared in Comparative Example 1), and Bi2SeO2 / Bi3Se4 (Prepared in Comparative Example 2) used as anodes in sodium-ion batteries, after 5 cycles at a current density of 1 A / g. The plots show that the charge transfer impedance of Bi2Se3 / NiSe2@C-2# (2.42 Ω) after 5 cycles is significantly lower than that of NiSe2@C (5.69 Ω) and Bi2SeO2 / Bi3Se4 (6.33 Ω). The smaller charge transfer impedance indicates higher conductivity. For the Bi2Se3 / NiSe2@C-2# composite material prepared in Example 2, the high conductivity stems from its unique hierarchical structure, which provides channels for rapid electron transport. Furthermore, the formation of heterostructures within the material creates an internal electric field, further enhancing the rapid electron transport within the material.

[0075] Figure 8 The results show that the Bi2Se3 / NiSe2@C-2# composite material prepared in Example 2, when used as a sodium-ion battery anode material, exhibits an initial discharge specific capacity of 632.62 mAh / g and an initial coulombic efficiency of 73.9% at a current density of 0.5 A / g. After 600 cycles, the discharge specific capacity still reaches 399.79 mAh / g, demonstrating excellent long-cycle performance and high sodium storage capacity. The NiSe2@C composite material prepared in Comparative Example 1 has an initial discharge specific capacity of 602.54 mAh / g and a discharge specific capacity of 286.32 mAh / g after 600 cycles. The Bi2SeO2 / Bi3Se4 composite material prepared in Comparative Example 2 has an initial discharge specific capacity of 667.88 mAh / g at a current density of 0.5 A / g, but its discharge specific capacity is only 123.42 mAh / g after 82 cycles.

[0076] Figure 9 The results show that the composite material Bi2Se3 / NiSe2@C-2# prepared in Example 2, when used as a negative electrode material for sodium-ion batteries, exhibits an initial discharge specific capacity of 673.22 mAh / g at a current density of 1 A / g, and a discharge specific capacity of 430.17 mAh / g after 800 cycles, demonstrating excellent long-cycle performance. The composite material NiSe2@C prepared in Comparative Example 1 has an initial discharge specific capacity of 587.26 mAh / g, and a discharge specific capacity of 259 mAh / g after 500 cycles. The Bi2SeO2 / Bi3Se4 composite material prepared in Comparative Example 2 has a discharge specific capacity of only 79.68 mAh / g after 100 cycles at a current density of 1 A / g.

[0077] Figure 10The results show that the composite material Bi2Se3 / NiSe2@C-1# prepared in Example 1, when used as a sodium-ion battery anode material, exhibits an initial discharge specific capacity of 507.22 mAh / g and a discharge specific capacity of 301.08 mAh / g after 500 cycles. The composite material Bi2Se3 / NiSe2@C-3# prepared in Example 3, when used as a sodium-ion battery anode material, exhibits an initial discharge specific capacity of 438.71 mAh / g and a discharge specific capacity of 252.42 mAh / g after 236 cycles. These results indicate that the composite material Bi2Se3 / NiSe2@C-2# prepared in Example 2 possesses the best cycle performance and high sodium storage activity.

[0078] Figure 11 The results show that the composite material Bi2Se3 / NiSe2@C-2# prepared in Example 2, as a sodium-ion battery anode material, exhibits specific capacities of 381 mAh / g, 349 mAh / g, 344.6 mAh / g, 336.4 mAh / g, and 320.9 mAh / g at different current densities of 0.1 A / g, 0.2 A / g, 0.5 A / g, 1 A / g, and 2 A / g, respectively, demonstrating excellent capacity retention. The composite material Bi2Se3 / NiSe2@C-2# prepared in Example 2 also exhibits superior rate performance, exceeding that of Comparative Example 1 and Comparative Example 2.

[0079] Figure 12 The results show that the composite material Bi2Se3 / NiSe2@C-2# prepared in Example 2, when used as the negative electrode and assembled into a full cell with a sodium nickel iron manganese oxide positive electrode, still maintains a discharge specific capacity of 133.49 mAh / g after 3581 cycles at 1 A / g. These results indicate that the composite material with a potential-complementary heterojunction prepared by this method has better long-cycle performance and high-rate characteristics, making it a potential material for high-energy-density and high-power-density sodium-ion batteries.

[0080] The above description is merely an embodiment of the present invention and is not intended to limit the present invention in any way. The present invention can also have other embodiments based on the above structure and function, which will not be listed hereafter. Therefore, any simple modifications, equivalent changes, and alterations made by those skilled in the art to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing a composite material containing bismuth-nickel bimetallic selenide, characterized in that, Specifically, the following steps are included: (1) Ni(CH3COO)2•4H2O was dissolved in water to prepare solution A, and dimethylglyoxime was dissolved in anhydrous ethanol to prepare solution B. After mixing solutions A and B, the mixture was stirred in a constant temperature water bath for a certain period of time and then allowed to stand for further reaction. After the reaction was completed, the mixed solution was centrifuged and the upper clear liquid was discarded to obtain the lower precipitate. The precipitate was washed by centrifugation with anhydrous ethanol several times and then dried under vacuum to obtain the nickel dimethylglyoxime precursor. (2) The prepared nickel dimethylglyoxime precursor was heated to 400-800°C in an inert atmosphere and then kept at the temperature for 3-7 hours. After the temperature was kept at the temperature, it was naturally cooled to room temperature to obtain Ni@C. (3) Ni@C was added to an ethanol solution of Bi(NO3)3•5H2O. The mixture was stirred in a constant temperature water bath, then KI was added and stirring continued. After stirring, the resulting mixed solution was transferred to a reaction vessel for hydrothermal reaction. After the reaction, the resulting mixed solution was centrifuged and the supernatant was discarded to obtain the lower precipitate. The precipitate was washed by centrifugation with anhydrous ethanol several times and then dried under vacuum. The obtained sample was named BiOI / Ni@C precursor. (4) The BiOI / Ni@C precursor prepared in step (3) is mixed with selenium powder and then ground. After that, the selenization treatment is carried out by stage heating under an inert atmosphere. The stage heating process is as follows: first, the temperature is raised to 200~500℃, then the first isothermal treatment is carried out for 2~5 hours. After the first isothermal treatment, the temperature is raised to 500~800℃ and the second isothermal treatment is carried out for 1~4 hours. After natural cooling and cooling to room temperature, the composite material containing bismuth-nickel bimetallic selenide can be obtained.

2. The method for preparing the composite material containing bismuth-nickel bimetallic selenide as described in claim 1, characterized in that, In step (1), the mass concentration of Ni(CH3COO)2•4H2O in solution A is 10~15mg / mL, the mass concentration of dimethylglyoxime in solution B is 4~8mg / mL, and the volume ratio of solution A to solution B is 2:1~1:

3.

3. The method for preparing the composite material containing bismuth-nickel bimetallic selenide as described in claim 1, characterized in that, In step (1), the temperature of the constant temperature water bath is 25~45℃, the stirring reaction time is 1~3 hours, the standing reaction time is 4~9 hours, the centrifugation speed is 5000~10000 rpm, and the centrifugation time is 5~15 minutes; the vacuum drying temperature is 50~80℃.

4. The method for preparing the composite material containing bismuth-nickel bimetallic selenide as described in claim 1, characterized in that, In step (2), the inert atmosphere is N2 atmosphere, and the heating rate is 1~3℃ / min.

5. The method for preparing the composite material containing bismuth-nickel bimetallic selenide as described in claim 1, characterized in that, In step (3), the ethanol solution of Bi(NO3)3•5H2O is obtained by dissolving Bi(NO3)3•5H2O in anhydrous ethanol.

6. The method for preparing the composite material containing bismuth-nickel bimetallic selenide as described in claim 1, characterized in that, In step (3), the mass of Ni@C is 0~300mg, the mass concentration of bismuth nitrate is 1~3mg / mL, and the molar ratio of Bi(NO3)3•5H2O to KI is 1:0.5~1:

2.

7. The method for preparing the composite material containing bismuth-nickel bimetallic selenide as described in claim 1, characterized in that, In step (3), the temperature of the constant temperature water bath is 25℃, the stirring reaction time is 0.5~2 hours, after adding KI, stirring is continued for 1~3 hours, the temperature of the hydrothermal reaction is 90~120℃, the hydrothermal reaction time is 5~8 hours, the centrifugation speed is 5000~10000 rpm, the centrifugation time is 5~15 minutes; the vacuum drying temperature is 50~80℃.

8. The method for preparing the composite material containing bismuth-nickel bimetallic selenide as described in claim 1, characterized in that, In step (4), the mass ratio of BiOI / Ni@C precursor to selenium powder is 1:1 to 1:3, the grinding time is 5 to 20 minutes, the inert atmosphere is N2 atmosphere, the temperature is raised to 200 to 500℃ at a heating rate of 1 to 5℃ / min during the stage heating process, and after the first isothermal treatment, the temperature is raised to 500 to 800℃ at a heating rate of 1 to 5℃ / min.

9. The composite material containing bismuth-nickel bimetallic selenide obtained by any of the preparation methods described in claims 1 to 8.

10. The application of the bismuth-nickel bimetallic selenide composite material as described in claim 9 as a negative electrode material for sodium-ion batteries.

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