One-dimensional carbon-coated copper selenide nanowire coaxial heterostructure, preparation method and application thereof

Abstract

The application discloses a one-dimensional carbon-coated copper selenide nanowire coaxial heterostructure material, a preparation method and application thereof. The preparation method comprises the following steps: adopting a vacuum chemical vapor transport method to heat and decompose copper acetylacetonate under a sealed condition to form a carbon-coated copper nanowire material, and then performing annealing treatment to obtain a one-dimensional carbon-coated copper nanowire material; and adopting a chemical vapor deposition method to perform selenization on the one-dimensional carbon-coated copper nanowire material by using a selenium source to obtain a one-dimensional carbon-coated copper selenide nanowire coaxial heterostructure material. The one-dimensional carbon-coated copper selenide nanowire coaxial heterostructure material is synthesized by using a vacuum chemical vapor transport and secondary selenization method, and the preparation efficiency is improved. Meanwhile, the one-dimensional structure of the one-dimensional carbon-coated copper selenide nanowire material has a relatively high specific surface area, and the external carbon layer improves the electronic conductivity and stability of the copper selenide, and the one-dimensional carbon-coated copper selenide nanowire material has a relatively high charge and discharge specific capacity.

Description

Technical Field

[0001] This invention relates to carbon-coated copper selenide nanowires, specifically to one-dimensional carbon-coated copper selenide nanowire coaxial heterostructures, their preparation methods, and applications, belonging to the fields of nanoscience and nano-carbon materials technology. Background Technology

[0002] One-dimensional atomic crystals have been extensively studied as electrode materials for ion batteries. Compared to bulk materials, one-dimensional materials offer many advantages, such as high specific surface area with active sites, continuous one-dimensional charge transport paths, and strain adaptation to volume expansion / contraction. However, using single-phase materials often cannot guarantee highly ideal device performance. For example, due to their small diameter, one-dimensional materials are prone to aggregation during ion insertion / extraction. Degradation of electrode integrity leads to significant irreversible capacity loss.

[0003] The design of core-shell heterostructures of one-dimensional atomic crystals provides a feasible approach to solving the above problems. To date, carbon nanotubes (CNTs) have been the main material used as shielding layers and conductive channels to improve the electrochemical performance of one-dimensional atomic crystals. CNT encapsulation can not only better adapt to the large volume changes during ion insertion / extraction and avoid particle aggregation, but also improve the conductivity of the electrodes and achieve efficient charge transport.

[0004] Meanwhile, rechargeable aqueous batteries are considered a valuable alternative to lithium-ion batteries for large-scale applications. Compared to organic lithium electrolytes, aqueous electrolytes have advantages such as high ionic conductivity, non-flammability, and environmental friendliness. Among these batteries, aqueous zinc-ion batteries stand out due to their high theoretical capacity (820 mAh g⁻¹). -1 Zinc, with its abundant and low-cost resources, has attracted widespread attention. To date, most research has focused on developing high-performance cathode materials, such as Prussian blue, manganese oxides, vanadium-based materials, and organic materials. While significant progress has been made in cathodes, problems with zinc metal anodes still severely hinder the practical application of aqueous rechargeable zinc batteries. Therefore, research on cathode materials is particularly important.

[0005] Currently, the main cathode materials for zinc-ion batteries include carbon materials and transition metal oxides (sulfides and selenides). Graphite-based carbon materials possess excellent electrical conductivity, making them ideal electrode materials; however, their relatively low charge-discharge specific capacity limits their development. Transition metal oxides, sulfides, and selenides exhibit higher specific capacities and represent important development directions for zinc-ion batteries. Through continuous experimental research, it has been found that selenides outperform oxides and sulfides in terms of operating voltage and specific capacity. However, they still exhibit various problems and drawbacks, such as low electronic conductivity and significant irreversible capacity loss. These shortcomings limit the application of transition metal selenides in zinc-ion batteries. Furthermore, there are currently few methods for preparing one-dimensional carbon-coated copper selenide nanowires, resulting in low preparation efficiency. Therefore, finding a cathode material with good cycle stability and high discharge specific capacity is particularly important. Summary of the Invention

[0006] The main objective of this invention is to provide a one-dimensional carbon-coated copper selenide nanowire coaxial heterostructure and its preparation method, so as to overcome the shortcomings of the prior art.

[0007] Another object of the present invention is to provide the application of the one-dimensional carbon-coated copper selenide nanowire coaxial heterostructure.

[0008] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0009] This invention provides a method for preparing a one-dimensional carbon-coated copper selenide nanowire coaxial heterostructure, comprising:

[0010] A vacuum chemical vapor transport method was used to heat and decompose copper acetylacetone under sealed conditions to form carbon-coated copper nanowire materials.

[0011] The carbon-coated copper nanowire material was annealed to obtain a one-dimensional carbon-coated copper nanowire material.

[0012] One-dimensional carbon-coated copper nanowires were selenized using a selenium source via chemical vapor deposition to prepare a one-dimensional carbon-coated selenized copper nanowire coaxial heterostructure.

[0013] This invention also provides a one-dimensional carbon-coated copper selenide nanowire coaxial heterostructure prepared by the aforementioned method, comprising coaxially arranged copper selenide nanowires and a one-dimensional carbon nanotube layer, wherein the one-dimensional carbon nanotube layer coats the outside of the copper selenide nanowires.

[0014] This invention also provides the application of the one-dimensional carbon-coated copper selenide nanowire coaxial heterostructure in the preparation of zinc-ion battery cathode materials.

[0015] Accordingly, embodiments of the present invention also provide a zinc-ion battery cathode, which includes the aforementioned one-dimensional carbon-coated copper selenide nanowire coaxial heteromaterial.

[0016] This invention also provides a zinc-ion battery, including a positive electrode, a negative electrode, and an electrolyte, wherein the positive electrode is the aforementioned zinc-ion battery positive electrode.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] This invention utilizes vacuum chemical vapor transport and a secondary selenization method to synthesize a one-dimensional carbon-coated copper selenide nanowire coaxial heterostructure, enriching the preparation methods of one-dimensional carbon-coated copper selenide materials and improving preparation efficiency. Simultaneously, the one-dimensional carbon-coated copper selenide nanowire material constructed by this invention possesses a high specific surface area, while the external carbon layer enhances the electronic conductivity and stability of copper selenide, exhibiting higher charge-discharge specific capacity and better electrochemical performance. It can be used as a positive electrode in zinc-ion batteries, providing a novel one-dimensional electrode material suitable for aqueous zinc-ion batteries. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the preparation process of one-dimensional carbon-coated copper selenide nanowire coaxial heterostructure in a typical embodiment of the present invention;

[0021] Figure 2a and Figure 2b This is a SEM image of the CuSe@CNT coaxial heteromaterial in Embodiment 1 of the present invention;

[0022] Figure 2c This is the SAED diagram of the CuSe@CNT coaxial heteromaterial in Embodiment 1 of the present invention;

[0023] Figure 2d and Figure 2e This is an HRTEM image of the CuSe@CNT coaxial heteromaterial in Example 1 of this invention;

[0024] Figure 2f This is the HAADF diagram of the CuSe@CNT coaxial heteromaterial in Embodiment 1 of the present invention;

[0025] Figure 2g-Figure 2iThis is the EDS-Mapping diagram of the CuSe@CNT coaxial heteromaterial in Embodiment 1 of the present invention;

[0026] Figure 3a This is the XRD pattern of the CuSe@CNT coaxial heteromaterial in Example 1 of this invention;

[0027] Figure 3b and Figure 3c This is the XPS spectrum of the CuSe@CNT coaxial heteromaterial in Example 1 of this invention;

[0028] Figure 4a This is the CV curve of the CuSe@CNT carbon cloth / Zn ion battery in Example 1 of this invention;

[0029] Figure 4b This is a long-cycle curve of the CuSe@CNT carbon cloth / Zn ion battery in Example 1 of the present invention;

[0030] Figure 5a , Figure 5b The images shown are SEM images and battery performance diagrams of the material obtained in Comparative Example 1 without annealing of the carbon-coated copper nanowire material.

[0031] Figure 6a , Figure 6b The images show the SEM morphology and battery performance of the material obtained by directly mixing copper acetylacetone and selenium source in Comparative Example 2. Detailed Implementation

[0032] In response to the shortcomings of existing technologies, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention, which mainly constructs a stable one-dimensional carbon-coated copper selenide nanowire material through chemical vapor phase transport and further selenization methods.

[0033] The following will further explain the technical solution, its implementation process, and its principles. However, it should be understood that within the scope of this invention, the above-mentioned technical features of this invention and the technical features specifically described below (in embodiments) can be combined with each other to form new or preferred technical solutions. Due to space limitations, they will not be described in detail here.

[0034] As one aspect of the technical solution of this invention, the method for preparing one-dimensional carbon-coated copper selenide nanowire coaxial heteromaterials includes:

[0035] A vacuum chemical vapor transport method was used to heat and decompose copper acetylacetone under sealed conditions to form carbon-coated copper nanowire materials.

[0036] The carbon-coated copper nanowire material was annealed to obtain a one-dimensional carbon-coated copper nanowire material.

[0037] One-dimensional carbon-coated copper nanowires were selenized using a selenium source via chemical vapor deposition to prepare a one-dimensional carbon-coated copper selenide nanowire coaxial heterostructure (hereinafter also referred to as "CuSe@CNT coaxial heterostructure").

[0038] In some preferred embodiments, the preparation method includes: under a vacuum degree below 10... -5 Under Pa conditions, copper acetylacetonate was sealed in a container and then heated at 400–800 °C for 12–72 h to decompose the copper acetylacetonate and form carbon-coated copper nanowires with a coaxial structure.

[0039] Furthermore, the growth temperature of the vacuum chemical vapor transport method is the key influencing factor in this invention, and the growth temperature of the vacuum chemical vapor transport method can be 400℃~800℃.

[0040] Furthermore, the growth time of the vacuum chemical vapor transport method is the key influencing factor in this invention. The commonly used growth time is 12 to 72 hours, and preferably 36 to 72 hours.

[0041] Furthermore, the preparation method includes raising the temperature to 400–800°C at a heating rate of 10–50°C / min. The heating rate is an auxiliary influencing factor; 10–50°C / min is a commonly used heating rate for growing one-dimensional carbon-coated copper selenide nanowires.

[0042] In some preferred embodiments, to improve the crystallinity of the carbon layer, the preparation method further includes: annealing the carbon-coated copper nanowire material in a mixed atmosphere of hydrogen and inert gas to obtain a one-dimensional carbon nanotube-coated copper nanowire structure, wherein the annealing temperature is 500-800°C and the time is 30 min-2 h.

[0043] Furthermore, the inert gas may be argon, but is not limited to this.

[0044] Furthermore, the volume ratio of hydrogen to inert gas is 10:90 to 50:50.

[0045] In some preferred embodiments, the preparation method includes: using chemical vapor deposition (CVD), placing a selenium source in a first region of the reaction chamber of a CVD apparatus, placing a one-dimensional carbon-coated copper nanowire material in a second region of the reaction chamber, heating the selenium source to allow it to enter the second region under the action of a carrier gas, selenizing the one-dimensional carbon-coated copper nanowire material, and then rapidly cooling (at a cooling rate of 20°C / min to 50°C / min) to room temperature to obtain a one-dimensional carbon-coated copper selenide nanowire coaxial heterostructure. The first and second regions are arranged sequentially along the direction of the carrier gas flow.

[0046] Furthermore, the first region can be defined as the upstream area, and the second region as the central temperature zone.

[0047] In some preferred embodiments, the heating temperature of the first region is 200–300°C.

[0048] In some preferred embodiments, the heating temperature of the second region is 500–600°C, and the heating time is 0.5–2 hours.

[0049] Furthermore, the carrier used in the selenization construction of one-dimensional carbon-coated copper selenide nanowires of the present invention includes a mixture of hydrogen and inert gas. Specifically, during the growth process, the flow rate of the inert gas is 80-200 sccm, and the flow rate of the hydrogen is 20-50 sccm.

[0050] Furthermore, the mass ratio of copper acetylacetone to selenium source is 120–300:5–10.

[0051] Furthermore, the selenium source comprises selenium powder (Se, Alfa-Aesar) with a purity of 99.9%.

[0052] Furthermore, the preparation method also includes: the cooling process after selenization is a rapid cooling process, in which the quartz tube is directly removed from the high-temperature zone and rapidly (cooling rate 20℃ / min~50℃ / min) cooled to room temperature.

[0053] As one of the more preferred implementation schemes, please refer to Figure 1 As shown, the growth of the one-dimensional carbon-coated copper selenide nanowire coaxial heterostructure mainly involves vacuum chemical vapor transport and atmospheric pressure chemical vapor deposition (APCVD). The selection of the precursor and the growth conditions, namely the heating rate, growth temperature, growth time, gas flow rate, and cooling program, are all key technical indicators. The specific preparation steps are as follows:

[0054] 1) Using the MRVS1003 single-station vacuum tube sealing machine and a single-zone tube furnace CVD system: Thermo Scientific LBM1100℃ Mini-Mite™ single-zone tube furnace;

[0055] 2) Growth precursors: Copper acetylacetonate (Cu(acac)2, 120-300 mg, Alfa-Aesar) and selenium powder (Se, 5-10 mg, Alfa-Aesar), both with a purity of 99.9%. These precursors are crucial for the growth of one-dimensional carbon-coated copper selenide nanowires and cannot be arbitrarily replaced; otherwise, one-dimensional carbon-coated copper selenide nanowires cannot be grown.

[0056] 3) Quartz tube: 15mm or 20mm in diameter, 10cm in length;

[0057] 4) Using copper acetylacetone as the raw material, weigh 120-300 mg of copper acetylacetone in advance and place it in a custom-made quartz tube. A long tubular device should be used during placement to prevent it from sticking to the quartz tube wall and affecting the subsequent sealing operation. After placing the raw material, place a quartz column in the quartz tube, and then use a vacuum sealing machine to remove the air from the quartz tube, maintaining the pressure at a low level (approximately 10). -5 Pa), and then sintered it together with a quartz tube using a high-temperature flame gun to achieve the purpose of sealing copper acetylacetonate under low pressure.

[0058] 5) The sealed quartz tube is placed in an environment of 400–800℃ and heated for 12–72 hours. Under these conditions, copper acetylacetonate decomposes and forms carbon-coated copper nanowire material (i.e., "coaxial structure of Cu@C"). However, at this time, the crystallinity of the carbon layer nested outside the copper nanowire is poor. To improve the crystallinity of the carbon layer, the Cu@C obtained in the previous step is annealed in a mixed atmosphere of hydrogen and argon at 500–800℃ for 30 min–2 h to obtain one-dimensional carbon-coated copper nanowire material (i.e., "Cu@CNT").

[0059] In the vacuum chemical vapor transport growth process in step 5), the heating rate can be 10-50℃ / min, the growth temperature can be 400℃-800℃, and the growth time can be 12-72h. Different growth conditions correspond to different growth densities and lengths of the one-dimensional carbon-coated copper selenide nanowires.

[0060] 6) Finally, selenium powder is used to selenize Cu@CNT. In a tube furnace, the selenium powder is placed upstream and heated to 200-300℃. Cu@CNT is placed in the central temperature zone and heated to 500-600℃. The temperature is maintained for 0.5-2 hours to obtain a one-dimensional carbon-coated copper selenide nanowire coaxial heterostructure, namely the coaxial heterostructure of CuSe@CNT.

[0061] Furthermore, in step 6), Ar and H2 are used as carrier gases to construct one-dimensional carbon-coated copper selenide nanowires. The quartz channel is cleaned before growth, and the Ar flow rate is 80-200 sccm and the hydrogen flow rate is 20-50 sccm during growth.

[0062] Furthermore, in step 6), the cooling process after selenization is a rapid cooling process, in which the quartz tube is directly removed from the high-temperature zone and rapidly cooled to room temperature.

[0063] Another aspect of the present invention provides coaxially arranged copper selenide nanowires and a one-dimensional carbon nanotube layer prepared by the aforementioned preparation method, wherein the one-dimensional carbon nanotube layer coats the outside of the copper selenide nanowires.

[0064] Furthermore, the copper selenide nanowires have a length of 5μm to 50μm and a diameter of 50nm to 200nm.

[0065] Furthermore, the thickness of the one-dimensional carbon nanotube layer is 20 nm to 100 nm.

[0066] Furthermore, the content of copper selenide nanowires in the one-dimensional carbon-coated copper selenide nanowire coaxial heteromaterial is 60-90 wt%, and the content of one-dimensional carbon nanotubes is 10-40 wt%.

[0067] The CuSe@CNT obtained by this invention has a high specific surface area in its one-dimensional structure. At the same time, the external carbon layer improves the electronic conductivity and stability of CuSe, resulting in higher charge-discharge specific capacity, higher stability, and better electrochemical performance.

[0068] Another aspect of this invention provides the application of the aforementioned one-dimensional carbon-coated copper selenide nanowire coaxial heterostructure in the preparation of zinc-ion battery cathode materials.

[0069] Accordingly, another aspect of the present invention provides a novel one-dimensional zinc-ion battery electrode material that can be used in aqueous zinc-ion batteries, which is composed of the aforementioned one-dimensional carbon-coated copper selenide nanowire coaxial heterostructure.

[0070] Accordingly, another aspect of the present invention provides a zinc-ion battery, including a positive electrode, a negative electrode and an electrolyte, wherein the positive electrode is the aforementioned zinc-ion battery positive electrode.

[0071] By means of the above technical solution, the present invention synthesizes one-dimensional carbon-coated copper selenide nanowire coaxial heterostructure using vacuum chemical vapor transport and secondary selenization method, thereby improving the preparation efficiency. At the same time, the one-dimensional carbon-coated copper selenide nanowire material constructed by the present invention has a high specific surface area, and the outer carbon layer improves the electronic conductivity and stability of copper selenide, thus exhibiting a high charge-discharge specific capacity.

[0072] To make the objectives, technical solutions, and applications of this invention clearer, the technical solutions of this invention will be further described in detail below with reference to several preferred embodiments and accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention. The implementation conditions used in the following embodiments can be further adjusted according to actual needs; implementation conditions not specified are generally conditions in conventional experiments.

[0073] Example 1

[0074] like Figure 1 As shown, the specific preparation steps of the one-dimensional carbon-coated copper selenide nanowire coaxial heterostructure in this embodiment include:

[0075] 1) Using the MRVS1003 single-station vacuum tube sealing machine and a single-zone tube furnace CVD system: Thermo Scientific LBM1100℃ Mini-Mite™ single-zone tube furnace;

[0076] 2) Growth precursors: Copper acetylacetonate (Cu(acac)2, 120 mg, Alfa-Aesar) and selenium powder (Se, 10 mg, Alfa-Aesar), both with a purity of 99.9%. The raw materials used for growth are crucial for the growth of one-dimensional carbon-coated copper selenide nanowires and cannot be arbitrarily replaced; otherwise, one-dimensional carbon-coated copper selenide nanowires cannot be grown.

[0077] 3) Quartz tube: 15mm in diameter and 10cm in length;

[0078] 4) Using copper acetylacetonate as the raw material, weigh 120mg of copper acetylacetonate in advance and place it in a custom-made quartz tube. A long tubular device should be used during placement to prevent it from sticking to the quartz tube wall and affecting the subsequent sealing operation. After placing the raw material, place a quartz column in the quartz tube, and then use a vacuum sealing machine to remove the air from the quartz tube, maintaining the pressure at a low level (approximately 10). -5 Pa), and then sintered it together with a quartz tube using a high-temperature flame gun to achieve the purpose of sealing copper acetylacetonate under low pressure.

[0079] 5) The sealed quartz tube was placed in an environment of 400℃ (heating rate of 10℃ / min) and heated for 72 hours. Under these conditions, copper acetylacetonate decomposed and formed carbon-coated copper nanowire material (i.e., "coaxial structure of Cu@C"). However, at this time, the crystallinity of the carbon layer nested outside the copper nanowire was poor. To improve the crystallinity of the carbon layer, the Cu@C obtained in the previous step was annealed at 600℃ for 2 hours in a mixed atmosphere of hydrogen and argon (volume ratio of hydrogen to argon of 10:90) to obtain one-dimensional carbon-coated copper nanowire material (i.e., "Cu@CNT").

[0080] 6) Finally, selenization of Cu@CNT was carried out using selenium powder. In a tube furnace, the flow rate of argon was 80 sccm and the flow rate of hydrogen was 20 sccm. The selenium powder was placed upstream, the mass ratio of copper acetylacetonate to selenium source was 120:5, and the heating temperature was 300℃. Cu@CNT was placed in the central temperature zone and heated to 500℃ for 2 hours. Then, it was cooled to room temperature at a rate of 20℃ / min to obtain a one-dimensional carbon-coated copper selenide nanowire coaxial heterostructure, namely the coaxial heterostructure of CuSe@CNT.

[0081] The inventors in this case characterized the morphology and structure of the CuSe@CNT samples using scanning electron microscopy. Please refer to [link / reference]. Figure 2a and Figure 2b The image shown is a SEM image of the CuSe@CNT coaxial heterostructure. Figure 2c SAED image of CuSe@CNT coaxial heterostructure. HRTEM image of CuSe@CNT coaxial heterostructure is shown below. Figure 2d and Figure 2e As shown. The inventors further characterized its structure using transmission electron microscopy, as shown in the HAADF image. Figure 2f As shown, the EDS-Mapping element spectrum is as follows: Figure 2g-Figure 2i As shown, the composition of its coaxial heterostructure can be clearly seen.

[0082] Figure 3a The XRD pattern of the CuSe@CNT coaxial heterostructure obtained in this embodiment shows that it conforms well to the standard PDF card (JCPDs NO.86-1239). Figure 3b and Figure 3c The results show the chemical composition and elemental valence states of the CuSe@CNT coaxial heterostructure analyzed using X-ray photoelectron spectroscopy (XPS).

[0083] The inventors in this case also studied the electrochemical performance of the CuSe@CNT carbon cloth / Zn ion battery through cyclic voltammetry (CV) and charge-discharge performance testing. Figure 4a The CV curves of CuSe@CNT carbon cloth / Zn ion batteries were tested under the conditions of a scanning rate of 0.5 mV / s and a scanning point of 0.-1.5 V. Figure 4b The long-cycle curves of CuSe@CNT carbon cloth / Zn ion batteries are shown.

[0084] Example 2

[0085] The difference between this embodiment and Embodiment 1 is that:

[0086] 5) The sealed quartz tube was placed in an environment of 500℃ (heating rate of 20℃ / min) and heated for 60h. Under these conditions, copper acetylacetonate decomposed to form carbon-coated copper nanowire material (Cu@C). The Cu@C obtained in the previous step was annealed at 600℃ for 2h in a mixed atmosphere of hydrogen and argon (volume ratio of hydrogen to argon of 20:80) to obtain one-dimensional carbon-coated copper nanowire material (Cu@CNT).

[0087] 6) Finally, selenization of Cu@CNT was carried out using selenium powder. In a tube furnace, the flow rate of argon was 150 sccm and the flow rate of hydrogen was 50 sccm. The selenium powder was placed upstream, the mass ratio of copper acetylacetonate to selenium source was 180:8, and the heating temperature was 250℃. Cu@CNT was placed in the central temperature zone and heated to 600℃ for 0.5 h. Then, it was cooled to room temperature at a rate of 40℃ / min to obtain a one-dimensional carbon-coated copper selenide nanowire coaxial heterostructure, namely the coaxial heterostructure of CuSe@CNT.

[0088] Example 3

[0089] The difference between this embodiment and Embodiment 1 is that:

[0090] 5) The sealed quartz tube was placed in an environment of 800℃ (heating rate of 50℃ / min) and heated for 12 hours. Under these conditions, copper acetylacetonate decomposed to form carbon-coated copper nanowire material (Cu@C). The Cu@C obtained in the previous step was annealed at 800℃ for 30 minutes in a mixed atmosphere of hydrogen and argon (volume ratio of hydrogen to argon of 40:60) to obtain one-dimensional carbon-coated copper nanowire material (Cu@CNT).

[0091] 6) Finally, selenization of Cu@CNT was carried out using selenium powder. In a tube furnace, the flow rate of argon was 200 sccm and the flow rate of hydrogen was 40 sccm. The selenium powder was placed upstream, the mass ratio of copper acetylacetonate to selenium source was 300:10, and the heating temperature was 200℃. Cu@CNT was placed in the central temperature zone and heated to 550℃ for 1 hour. Then, it was cooled to room temperature at a rate of 50℃ / min to obtain a one-dimensional carbon-coated copper selenide nanowire coaxial heterostructure, namely the coaxial heterostructure of CuSe@CNT.

[0092] Example 4

[0093] The difference between this embodiment and Embodiment 1 is that:

[0094] 5) The sealed quartz tube was placed in an environment of 600℃ (heating rate of 30℃ / min) and heated for 36 hours. Under these conditions, copper acetylacetonate decomposed to form carbon-coated copper nanowire material (Cu@C). The Cu@C obtained in the previous step was annealed at 500℃ for 2 hours in a mixed atmosphere of hydrogen and argon (volume ratio of hydrogen to argon of 50:50) to obtain one-dimensional carbon-coated copper nanowire material (Cu@CNT).

[0095] 6) Finally, selenization of Cu@CNT was carried out using selenium powder. In a tube furnace, the flow rate of argon was 120 sccm and the flow rate of hydrogen was 30 sccm. The selenium powder was placed upstream, the mass ratio of copper acetylacetonate to selenium source was 200:6, and the heating temperature was 270℃. Cu@CNT was placed in the central temperature zone and heated to 580℃ for 1 hour. Then, it was cooled to room temperature at a rate of 30℃ / min to obtain a one-dimensional carbon-coated copper selenide nanowire coaxial heterostructure, namely the coaxial heterostructure of CuSe@CNT.

[0096] Comparative Example 1

[0097] This comparative example differs from Example 1 in that it lacks the step of annealing the carbon-coated copper nanowire material. The SEM morphology of the final obtained material is as follows. Figure 5a As shown, the battery performance is as follows Figure 5b As shown in the figure. The results indicate that annealing the carbon-coated copper nanowire material can improve the crystallinity of the carbon layer. Without annealing, the outer carbon layer has poor crystallinity, and the specific capacity of the battery decays rapidly.

[0098] Comparative Example 2

[0099] The comparative example used a method of directly mixing copper acetylacetone and a selenium source before reaction. The SEM morphology of the final material is shown below. Figure 6a As shown, the battery performance is as follows Figure 6b As shown in the figure. The results indicate that directly mixing copper acetylacetone and selenium source and reacting them yields only particulate materials with poor electrochemical stability and low specific capacity.

[0100] In addition, the inventors of this case also conducted experiments with other raw materials, process operations, and process conditions described in this specification, referring to the aforementioned embodiments, and obtained relatively ideal results in all cases.

[0101] It should be understood that the examples described above are merely illustrative of the technical concept and features of the present invention, intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly, and should not be used to limit the scope of protection of the present invention. All equivalent transformations or modifications made according to the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a one-dimensional carbon-coated copper selenide nanowire coaxial heterostructure, characterized in that, include: Vacuum chemical vapor transport method is used, with a vacuum degree below 10 -5 Under the condition of Pa, copper acetylacetonate was sealed in a container and then heated at 400~800℃ for 12~72 h to decompose copper acetylacetonate and form carbon-coated copper nanowire material with coaxial structure. The carbon-coated copper nanowire material is annealed in a mixed atmosphere of hydrogen and inert gas to obtain a one-dimensional carbon-coated copper nanowire material; the annealing temperature is 500~800℃ and the time is 30 min~2 h. A chemical vapor deposition (CVD) method was used. A selenium source was placed in the first region of the reaction chamber of the CVD apparatus, and a one-dimensional carbon-coated copper nanowire material was placed in the second region of the reaction chamber. The selenium source was heated and introduced into the second region under the action of a carrier gas to selenize the one-dimensional carbon-coated copper nanowire material. The material was then cooled to room temperature at a rate of 20 °C / min to 50 °C / min to obtain a one-dimensional carbon-coated copper selenide nanowire coaxial heterostructure. The first and second regions were arranged sequentially along the direction of the carrier gas. The heating temperature of the first region was 200–300 °C, and the heating temperature of the second region was 500–600 °C for 0.5–2 h. The mass ratio of copper acetylacetonate to the selenium source was 120–300:5–10, and the selenium source was selenium powder.

2. The preparation method according to claim 1, characterized in that, include: When the vacuum level is below 10 -5 Under Pa conditions, copper acetylacetonate was sealed in a container and then heated at 400-800℃ for 36-72 h to decompose the copper acetylacetonate and form carbon-coated copper nanowires with a coaxial structure.

3. The preparation method according to claim 1 or 2, characterized in that: The temperature is raised to 400-800℃ at a heating rate of 10-50℃ / min.

4. The preparation method according to claim 1, characterized in that: The inert gas is argon.

5. The preparation method according to claim 1, characterized in that: The volume ratio of hydrogen to inert gas is 10:90 to 50:

50.

6. The preparation method according to claim 1, characterized in that: The carrier gas is a mixture of hydrogen and an inert gas, with the inert gas having a flow rate of 80-200 sccm and the hydrogen having a flow rate of 20-50 sccm.

7. A one-dimensional carbon-coated copper selenide nanowire coaxial heterostructure prepared by the preparation method according to any one of claims 1-6, characterized in that, The material includes coaxially arranged copper selenide nanowires and a one-dimensional carbon nanotube layer, wherein the one-dimensional carbon nanotube layer coats the copper selenide nanowires. The content of copper selenide nanowires in the one-dimensional carbon-coated copper selenide nanowire coaxial heteromaterial is 60-90 wt%, and the content of one-dimensional carbon nanotubes is 10-40 wt%.

8. The one-dimensional carbon-coated copper selenide nanowire coaxial heterostructure according to claim 7, characterized in that: The copper selenide nanowires have a length of 5 μm to 50 μm and a diameter of 50 nm to 200 nm.

9. The one-dimensional carbon-coated copper selenide nanowire coaxial heterostructure according to claim 7, characterized in that: The thickness of the one-dimensional carbon nanotube layer is 20 nm to 100 nm.

10. The application of the one-dimensional carbon-coated copper selenide nanowire coaxial heterostructure according to any one of claims 7-9 in the preparation of zinc-ion battery cathode materials.

11. A zinc-ion battery positive electrode, characterized in that, The one-dimensional carbon-coated copper selenide nanowire coaxial heterostructure includes any one of claims 7-9.

12. A zinc-ion battery, comprising a positive electrode, a negative electrode, and an electrolyte, characterized in that, The positive electrode is the zinc-ion battery positive electrode as described in claim 11.

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