Dual-carbon confinement phosphorus-doped copper sulfide nano composite material and method and application thereof

Abstract

The invention discloses a dual-carbon confinement phosphorus-doped copper sulfide nano composite material and a method and application thereof, and belongs to the technical field of sodium ion battery negative electrode materials, the dual-carbon confinement phosphorus-doped copper sulfide nano composite material comprises internal carbon nanotubes, middle-layer microspheres formed by clustering phosphorus-doped copper sulfide nanosheets, and an outer-layer carbon shell coating layer. The preparation method comprises the following steps: dissolving carbon nanotubes, a copper source, a sulfur source, a phosphorus source and a carbon source in deionized water, uniformly stirring, carrying out a hydrothermal reaction, carrying out centrifugal cleaning, collecting a precipitation product, and carrying out a calcination reaction to obtain the dual-carbon confinement phosphorus-doped copper sulfide nano composite material. The preparation process is simple, the cost is low, the dual-carbon confinement can effectively buffer the volume change of the active material, the electron conduction rate of the material system can be improved, the performance of the sodium-ion battery is improved, and the method is suitable for industrial production and large-scale energy storage. And the material has certain advantages in the application of sodium-ion battery negative electrode materials.

Description

Technical Field

[0001] The present invention belongs to the technical field of anode materials for sodium-ion batteries, and particularly relates to a dual-carbon-confined phosphorus-doped copper sulfide nanocomposite material, method and application thereof. Background Art

[0002] In today's world, the rapid growth of energy demand and the high dependence on fossil fuels are increasingly intensifying the global energy crisis and environmental pollution. Finding clean, efficient and sustainable energy storage solutions has become an urgent challenge. As the most mature and widely used energy storage technology at present, lithium-ion batteries (LIBs) have achieved great success in the fields of portable electronic devices and electric vehicles. However, the uneven distribution of lithium resources globally and the increasing demand have led to a continuous increase in the price of lithium resources, and the limited nature of lithium resources itself has also raised concerns about the sustainability of lithium-ion batteries. At the same time, sodium, as one of the most abundant alkali metal elements in the earth's crust, has a uniform resource distribution and low cost, making sodium-ion batteries (SIBs), a sodium-based energy storage technology, a very promising next-generation energy storage system. Sodium-ion batteries not only have significant advantages in terms of raw material cost, but also have similar electrochemical characteristics to lithium-ion batteries, and theoretically can achieve energy storage performance comparable to that of lithium-ion batteries. However, the sodium ion radius is much larger than the lithium ion radius, which leads to relatively slow diffusion kinetics of sodium ions in the electrode material and is prone to cause larger volume expansion during charge and discharge, resulting in a significant decline in the rate performance and cycle stability of the electrode material, seriously restricting the practical application and commercialization process of sodium-ion batteries. Therefore, developing anode materials for sodium-ion batteries with excellent electrochemical performance is the key bottleneck and core problem to be solved urgently in promoting the development of sodium-ion battery technology.

[0003] Transition metal sulfides, especially copper sulfide (CuS)-based materials, exhibit great application prospects in the field of anode materials for sodium-ion batteries due to their unique physical and chemical properties, such as high theoretical specific capacity, low cost, abundant resources, and environmental friendliness. They are considered one of the ideal candidates to replace traditional carbon anode materials. Copper sulfide materials have a high theoretical specific capacity. For example, the theoretical specific capacity of CuS can reach 536 mAh / g, which is much higher than that of traditional graphite anodes. In addition, copper and sulfur elements are abundant in the earth's crust, making the preparation cost of copper sulfide-based materials relatively low, which better meets the requirements of large-scale energy storage applications. More importantly, copper sulfide materials are generally considered environmentally friendly, which highly coincides with the concept of sustainable development. However, despite the many theoretical advantages of copper sulfide-based materials, they still face a series of severe challenges in practical applications. First, copper sulfide materials have poor inherent conductivity and low electronic conductivity, which limits the electron transfer rate of electrode materials and results in poor rate performance. Second, during the sodiation and desodiation processes of copper sulfide, significant volume expansion and contraction occur. This drastic volume change will lead to the structural damage of electrode materials, the shedding of active substances, and electrode pulverization, ultimately resulting in the attenuation of cycle life. In addition, during the cycling process, copper sulfide may dissolve. Especially when the electrolyte penetrates into the material, the dissolved copper ions may migrate and deposit on the surface of the anode, forming dendrites, which affects the safety of the battery.

[0004] The above-mentioned inherent defects greatly hinder the practical application of copper sulfide materials as high-performance anode materials for sodium-ion batteries. Therefore, effectively modifying and optimizing the defects of copper sulfide materials is the key to fully realizing their potential and achieving high-performance sodium-ion batteries. Summary of the Invention

[0005] In order to overcome the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide a dual-carbon-confined phosphorus-doped copper sulfide nanocomposite material, method, and application to solve the technical problems of structural collapse during cycling, low capacity of sodium-ion batteries, and unsatisfactory rate performance existing in the existing anode materials for sodium-ion batteries.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions: The present invention discloses a dual-carbon-confined phosphorus-doped copper sulfide nanocomposite material, which includes a core, a middle-layer microsphere, and an outer shell coating layer; the core is a carbon core, the middle-layer microsphere is a micron sphere formed by clustering phosphorus-doped copper sulfide nanosheets, and the outer shell coating layer is a carbon layer.

[0007] Preferably, the diameter of the micron sphere formed by clustering phosphorus-doped copper sulfide nanosheets is 1-10 μm, and the thickness of the phosphorus-doped copper sulfide nanosheets is 1-100 nm.

[0008] Preferably, in the phosphorus-doped copper sulfide nanosheets, each 1 mol of copper sulfide contains 0.05 - 0.5 mol of phosphorus element.

[0009] Preferably, the carbon core is a carbon nanotube and the carbon layer is amorphous carbon.

[0010] The present invention also discloses a preparation method of a dual-carbon-confined phosphorus-doped copper sulfide nanocomposite, comprising the following steps: Dissolve carbon nanotubes, a copper source, a sulfur source, a carbon source and a phosphorus source in an ethylene glycol solution, stir and mix evenly, after hydrothermal reaction, centrifuge and wash, and collect the precipitate product; perform a calcination reaction on the precipitate product to obtain the dual-carbon-confined phosphorus-doped copper sulfide nanocomposite.

[0011] Preferably, the dosage ratio of the carbon nanotubes, the copper source, the sulfur source, the carbon source, the phosphorus source and the ethylene glycol solution is (0.01~1) g : (0.1~5) g : (0.1~5) g : (0.1~5) g : (0.05~5) mol : 80 mL; the ethylene glycol solution is prepared by mixing deionized water and ethylene glycol in a volume ratio of 3:1.

[0012] Preferably, the temperature of the hydrothermal reaction is 100~180 °C and the time of the hydrothermal reaction is 6~48 h.

[0013] Preferably, the copper source is any one of copper sulfate, copper nitrate and copper chloride; the sulfur source is any one of thiourea and thioacetamide; the carbon source is any one of glucose and dopamine; the phosphorus source is H3PO4.

[0014] Preferably, the temperature of the calcination reaction is 500~1000 °C; the time of the calcination reaction is 6~48 h.

[0015] The present invention also discloses the application of the above dual-carbon-confined phosphorus-doped copper sulfide nanocomposite in the preparation of a negative electrode material for a sodium ion battery.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention discloses a dual-carbon-confined phosphorus-doped copper sulfide nanocomposite, comprising an inner core, a middle-layer microsphere and an outer shell coating layer; the inner core is a carbon core, the middle-layer microsphere is a micron sphere formed by clustering phosphorus-doped copper sulfide nanosheets, and the outer shell coating layer is a carbon layer. The carbon core and the outer shell carbon coating layer tightly confine the micron sphere formed by clustering phosphorus-doped copper sulfide nanosheets in a limited space, improving the + structural stability of copper sulfide during the sodium insertion / extraction process. The carbon core and the carbon coating layer with good electronic conductivity and phosphorus doping ensure good battery rate performance of the copper sulfide negative electrode. The present invention solves the technical problems of the existing copper sulfide negative electrode material for sodium ion batteries, such as structural collapse during the cycling process, low capacity of the sodium ion battery and unsatisfactory rate performance.

[0017] Furthermore, the microspheres formed by clustering phosphorus-doped copper sulfide nanosheets are the basic units of the dual-carbon-confined phosphorus-doped copper sulfide nanocomposite. The diameter of the microspheres formed by clustering phosphorus-doped copper sulfide nanosheets is 1 - 10 μm, and the thickness of the phosphorus-doped copper sulfide nanosheets is 1 - 100 nm. The nanoscale has the advantage of a short ion diffusion path. In the battery reaction, it can ensure the rapid diffusion of electrons / ions, thereby improving the battery rate performance.

[0018] Furthermore, in the dual-carbon-confined phosphorus-doped copper sulfide nanocomposite, the internal carbon core is a carbon nanotube, and the external carbon layer is amorphous carbon. The dual-carbon confinement inside and outside can effectively protect the structural stability of the copper sulfide active material during the cycling process, ensuring the stability of the battery cycle. The lumen of the carbon nanotube can store more charges under the same volume, improving the energy density and endurance of the sodium-ion battery. During the discharging process, the expansion and contraction of the carbon nanotube negative electrode are more uniform, increasing the cycle stability, charge-discharge performance of the sodium-ion battery, and extending the cycle service life of the sodium-ion battery. The amorphous carbon material has good chemical stability and mechanical strength, and can resist the stress changes and chemical corrosion during the charge-discharge process of the battery, thereby extending the service life of the battery.

[0019] Furthermore, phosphorus and sulfur are adjacent in the periodic table and have similar atomic radii and electronegativities. Doping phosphorus atoms into the copper sulfide lattice can change the electronic structure of copper sulfide, adjust the energy band structure, increase the electronic conductivity, introduce lattice defects, increase the active sites, and further improve the battery performance of the copper sulfide negative electrode material.

[0020] The present invention also discloses a preparation method of the above-mentioned dual-carbon-confined phosphorus-doped copper sulfide nanocomposite. After dissolving carbon nanotubes, copper source, sulfur source, phosphorus source, and carbon source in a mixed solvent of deionized water and ethylene glycol and stirring and mixing them evenly, a hydrothermal reaction is carried out. After the reaction ends, the precipitate product is collected by centrifugation and washing. The obtained precipitate product is calcined and annealed. After the calcination reaction, the dual-carbon-confined phosphorus-doped copper sulfide nanocomposite is obtained. The preparation method of the present invention has a simple process and low cost. The dual-carbon confinement construction technology provides an opportunity to solve the problem of low performance of the copper sulfide negative electrode. The obtained dual-carbon-confined phosphorus-doped copper sulfide nanocomposite can play the advantage of buffering the volume change of the active material inside and outside, improve the performance of the sodium-ion battery, is suitable for industrial production, and is suitable for large-scale energy storage use.

[0021] Further, in a mixed solvent of 20 mL of ethylene glycol and 60 mL of deionized water, the addition amount of carbon nanotubes is 0.01 - 1 g, the addition amount of copper source is 0.1 - 5 g, the addition amount of sulfur source is 0.1 - 5 g, the addition amount of carbon source is 0.1 - 5 g; the addition amount of phosphorus source is 0.05 - 5 mol; the temperature of the hydrothermal reaction is 100 - 180 °C, and the time of the hydrothermal reaction is 6 - 48 h; within the given reaction condition range, an intermediate product of a double-carbon-confined phosphorus-doped copper sulfide nanocomposite material can be obtained, where phosphorus-doped copper sulfide coats the carbon nanotubes, and at the same time, amorphous carbon coats the surface of the phosphorus-doped copper sulfide.

[0022] The present invention also discloses the application of the above double-carbon-confined phosphorus-doped copper sulfide nanocomposite material in the preparation of a negative electrode material for a sodium-ion battery. This double-carbon-confined phosphorus-doped copper sulfide nanocomposite material can effectively buffer the volume change of the active material, synergistically enhance the capacity performance of the material, thereby improving the sodium-ion storage performance, and has certain advantages in the application of the negative electrode material for a sodium-ion battery. Description of the Drawings

[0023] Figure 1 It is a schematic diagram of the preparation process of the double-carbon-confined phosphorus-doped copper sulfide nanocomposite material disclosed by the present invention; Figure 2 It is an SEM image of the double-carbon-confined phosphorus-doped copper sulfide nanocomposite material disclosed in Example 1 of the present invention; Figure 3 It is an element distribution diagram of the double-carbon-confined phosphorus-doped copper sulfide nanocomposite material disclosed in Example 1 of the present invention. Detailed Embodiments

[0024] The technical solutions of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0025] In the present invention, if there is no special indication, all the embodiments and preferred implementation methods mentioned herein can be combined with each other to form a new technical solution.

[0026] In the present invention, if there is no special indication, all the technical features and preferred features mentioned herein can be combined with each other to form a new technical solution.

[0027] In the present invention, if there is no special indication, the percentage (%) or part refers to the weight percentage or weight part relative to the composition.

[0028] In the present invention, if there is no special indication, the various components or their preferred components involved can be combined with each other to form a new technical solution.

[0029] In the present invention, unless otherwise specified, the numerical range "a~b" represents an abbreviated representation of any real number combination between a and b, where both a and b are real numbers. For example, the numerical range "6~22" means that all real numbers between "6~22" have been fully listed herein, and "6~22" is only an abbreviated representation of these numerical combinations.

[0030] The "range" disclosed in the present invention can be in the form of one or more lower limits and one or more upper limits, respectively.

[0031] In the present invention, the term "and / or" used herein refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0032] In the present invention, unless otherwise specified, each reaction or operation step can be carried out sequentially or in order. Preferably, the reaction method herein is carried out sequentially.

[0033] Unless otherwise specified, the professional and scientific terms used herein have the same meanings as those familiar to persons skilled in the art. In addition, any method or material similar or equivalent to the described content can also be applied to the present invention.

[0034] The present invention discloses a dual-carbon-confined phosphorus-doped copper sulfide nanocomposite, which includes a core, a middle-layer microsphere, and an outer-shell coating layer; the core is a carbon core, the middle-layer microsphere is a microsphere formed by clustering phosphorus-doped copper sulfide nanosheets, and the outer-shell coating layer is a carbon layer. The carbon core and the outer-shell carbon coating layer tightly confine the microsphere formed by clustering phosphorus-doped copper sulfide nanosheets in a limited space, improving the structural stability of copper sulfide during the Na+ insertion / extraction process and solving the technical problem of structural collapse of the copper sulfide negative electrode material in the existing sodium-ion batteries during the cycling process.

[0035] The microsphere formed by clustering phosphorus-doped copper sulfide nanosheets is the basic unit of the dual-carbon-confined phosphorus-doped copper sulfide nanocomposite. The diameter of the microsphere is 1~10 μm, and the thickness of the phosphorus-doped copper sulfide nanosheet is 1~100 nm. The nanoscale has the advantage of a short ion diffusion path. In the battery reaction, it can ensure the rapid diffusion of electrons / ions, thereby improving the battery rate performance.

[0036] The phosphorus doping content is 0.05 - 0.5 mol of phosphorus element per 1 mol of copper sulfide. Phosphorus and sulfur are adjacent in the periodic table and have similar atomic radii and electronegativities. Doping phosphorus atoms into the copper sulfide lattice can change the electronic structure of copper sulfide, adjust the energy band structure, increase the electronic conductivity, and introduce lattice defects to increase the active sites, further improving the battery performance of the copper sulfide negative electrode material.

[0037] The carbon core is a carbon nanotube, and the carbon layer is amorphous carbon. The dual-carbon confinement inside and outside can effectively protect the structural stability of the copper sulfide active material during cycling, ensuring the stability of battery cycling. The lumen of the carbon nanotube can store more charges under the same volume, improving the energy density and endurance of the sodium-ion battery. During discharge, the expansion and contraction of the carbon nanotube negative electrode are more uniform, increasing the cycling stability, charge-discharge performance of the sodium-ion battery, and extending the cycling service life of the sodium-ion battery. The amorphous carbon material has good chemical stability and mechanical strength, capable of resisting stress changes and chemical corrosion during battery charge and discharge, thereby extending the service life of the battery.

[0038] The present invention also discloses a preparation method of the above-mentioned dual-carbon-confined phosphorus-doped copper sulfide nanocomposite, comprising the following steps: S1. Dissolve carbon nanotubes, a copper source, a sulfur source, a carbon source, and a phosphorus source in a mixed solution of deionized water and ethylene glycol (the volume ratio of deionized water to ethylene glycol is 3:1). After stirring and mixing evenly, perform a hydrothermal reaction. After the reaction ends, centrifuge and wash, and collect the precipitate product; S2. Calcinate the precipitate product obtained in step S1 to obtain the dual-carbon-confined phosphorus-doped copper sulfide nanocomposite.

[0039] In step S1, in every 80 mL of the mixed solvent of deionized water and ethylene glycol, the addition amount of carbon nanotubes is 0.01 - 1 g, the addition amount of the copper source is 0.1 - 5 g, the addition amount of the sulfur source is 0.1 - 5 g, the addition amount of the carbon source is 0.1 - 5 g; the addition amount of the phosphorus source is 0.05 - 5 mol; the temperature of the hydrothermal reaction is 100 - 180 °C, and the time of the hydrothermal reaction is 6 - 48 h. The copper source is any one of copper sulfate, copper nitrate, and copper chloride, the carbon source is any one of glucose and dopamine, and the sulfur source is any one of thiourea and thioacetamide. The phosphorus source is H3PO4.

[0040] In step S2, the temperature of the calcination reaction is 500 - 1000 °C; the time of the calcination reaction is 6 - 48 h.

[0041] The preparation method of the present invention has a simple process and low cost. The dual-carbon confinement construction technology provides an opportunity to solve the problem of low performance of copper sulfide anodes. The obtained dual-carbon confined phosphorus-doped copper sulfide nanocomposite can take advantage of the internal and external dual-carbon buffer to accommodate the volume change of the active material, improve the performance of sodium-ion batteries, be suitable for industrial production, and be suitable for large-scale energy storage applications. Within the given reaction conditions, intermediate products of the dual-carbon confined phosphorus-doped copper sulfide nanocomposite, carbon nanotubes coated with phosphorus-doped copper sulfide, and amorphous carbon-coated on the surface of phosphorus-doped copper sulfide can be obtained, providing specific and operable parameters for the preparation of composite materials with good performance. By appropriate calcination temperature and time, the crystal form transformation and structure adjustment of the material can be completed, and finally a dual-carbon confined phosphorus-doped copper sulfide nanocomposite with excellent performance can be obtained.

[0042] The present invention also discloses the application of the above dual-carbon confined phosphorus-doped copper sulfide nanocomposite in the preparation of anode materials for sodium-ion batteries. This dual-carbon confined phosphorus-doped copper sulfide nanocomposite can effectively buffer the volume change of the active material, synergistically enhance the capacity performance of the material, thereby improving the sodium-ion storage performance, and has certain advantages in the application of anode materials for sodium-ion batteries, solving the technical problems of low capacity and unsatisfactory rate performance of existing sodium-ion batteries.

[0043] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Usually, the components described and shown in the accompanying drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0044] Example 1 A preparation method of a dual-carbon confined phosphorus-doped copper sulfide nanocomposite, comprising the following steps: S1. Dissolve 0.01 g of carbon nanotubes, 0.1 g of copper nitrate, 0.1 g of thiourea, 0.1 g of glucose, and 0.05 mol of H3PO4 in a mixed solution of 60 mL of deionized water and 20 mL of ethylene glycol. After stirring and mixing evenly, transfer it to a hydrothermal autoclave and react at 100 °C for 6 h. After the reaction, centrifuge, wash, and collect the precipitate product; S2. Calcinate and anneal the product obtained in step S1 in a tubular furnace, and anneal at 500 °C for 48 h to obtain a dual-carbon confined phosphorus-doped copper sulfide nanocomposite.

[0045] The electrochemical test method of the obtained dual carbon-confined phosphorus-doped copper sulfide nanocomposite material is as follows: The button cell was used to study the electrochemical properties of the negative electrode material. The negative electrode used DMF as the solvent. The formula of the pole piece was prepared into a slurry according to the ratio of active material: PVDF: acetylene black = 7:2:1. The slurry was then evenly coated on the copper foil and placed in a vacuum drying oven at 80 °C for 12 h. After punching, the pole piece for the experimental battery was obtained. The metal sodium foil was used as the counter electrode, the electrolyte was a solution of 1.0M NaPF6 ethyl carbonate (EC and dimethyl carbonate (volume ratio 1:1), and the diaphragm was a celgard2400 membrane. The button cell was assembled in a glove box filled with argon atmosphere. The button cell was subjected to charge and discharge cycle tests: the charge and discharge cut-off voltage was 0.01~2.6V, and the charge and discharge current was 500mA / g.

[0046] Figure 1The present invention discloses a schematic diagram of the preparation process of a dual-carbon confined phosphorus-doped copper sulfide nanocomposite material; as can be seen from the figure, carbon nanotubes, copper source, sulfur source, carbon source and phosphorus source are dissolved in an ethylene glycol solution, stirred and mixed evenly, and after hydrothermal reaction, centrifuged and cleaned, and the precipitated product is collected; the precipitated product is subjected to a calcination reaction to obtain a dual-carbon confined phosphorus-doped copper sulfide nanocomposite material. The entire preparation process is concise and efficient. The carbon nanotubes, copper source, sulfur source, carbon source and phosphorus source are directly dissolved in an ethylene glycol solution, and each raw material can be evenly dispersed by simple stirring and mixing. This operation mode avoids complex raw material pretreatment and cumbersome mixing steps, greatly shortens the preparation cycle, and improves production efficiency. In the hydrothermal reaction stage, by accurately controlling the reaction temperature and time, the product morphology and structure can be precisely regulated. The phosphorus-doped copper sulfide nanosheets are clustered into micron-sized spheres in a specific way, and the diameter of the micron-sized spheres is ensured to be in the range of 1-10 μm and the thickness of the nanosheets is in the range of 1-100 nm. The nanometer size has the advantage of a short ion diffusion path. In the battery reaction, sodium ions can diffuse rapidly between the nanosheets, reducing the resistance of ion transmission. At the same time, electrons can also be quickly conducted in the nanostructure, ensuring the rapid diffusion of electrons / ions, thereby significantly improving the charge and discharge rate and rate performance of the battery. The prepared materials have consistent performance, providing a strong guarantee for large-scale industrial production. After hydrothermal reaction and calcination reaction, a dual-carbon confined structure was successfully constructed. The internal carbon nanotubes serve as the core support, and the external amorphous carbon layer forms a coating. This unique structure tightly confines the micron-sized spheres formed by the clusters of phosphorus-doped copper sulfide nanosheets in a limited space. During the charge and discharge process of the sodium ion battery, the dual-carbon confined structure can effectively buffer the volume change of the copper sulfide active material and prevent its structural collapse. When sodium ions are embedded and extracted, copper sulfide will expand and contract in volume, and the dual-carbon confined structure can act like a cushion to absorb and disperse the stress generated by this volume change, thereby significantly improving the structural stability of the material and extending the service life of the battery. Phosphorus doping changes the electronic structure of copper sulfide, adjusts the band structure, and increases electronic conductivity. At the same time, phosphorus doping also introduces lattice defects and increases active sites. In the battery reaction, more active sites can adsorb and store more sodium ions, improving the capacity performance of the battery. Moreover, good electronic conductivity enables electrons to be transmitted quickly, synergizing with ion diffusion to further improve the battery's rate performance.

[0047] Figure 2 This is an SEM image of the double-carbon-confined phosphorus-doped copper sulfide nanocomposite material disclosed in Example 1 of the present invention; as can be seen from the figure, the overall structure of the double-carbon-confined phosphorus-doped copper sulfide nanocomposite material presents nanoflower microspheres of nanosheet clusters, in which carbon nanotubes are interspersed inside the nanoflower microspheres, and the surface of the nanoflower microspheres is coated with a thin carbon shell coating.

[0048] Figure 3 This is an element distribution diagram of the double carbon-confined phosphorus-doped copper sulfide nanocomposite material disclosed in Example 1 of the present invention; as can be seen from the figure, copper, sulfur, carbon and phosphorus are evenly distributed, indicating that the double carbon-confined phosphorus-doped copper sulfide nanocomposite material has been successfully synthesized and prepared.

[0049] Example 2 A method for preparing a dual carbon-confined phosphorus-doped copper sulfide nanocomposite material comprises the following steps: S1. Dissolve 1g carbon nanotubes, 1g copper nitrate, 5g thiourea, 5g glucose and 5mol H3PO4 in a mixture of 60mlL deionized water and 20mL ethylene glycol, stir and mix well, transfer to a hydrothermal reactor, react at 180°C for 48h, and collect the precipitated product by centrifugation after the reaction is completed; S2. calcining and annealing the product obtained in step S1 in a tubular furnace at 1000° C. for 6 h to obtain a dual-carbon confined phosphorus-doped copper sulfide nanocomposite material.

[0050] The electrochemical testing method of the obtained dual-carbon confined phosphorus-doped copper sulfide nanocomposite material is the same as that of Example 1.

[0051] Example 3 A method for preparing a dual carbon-confined phosphorus-doped copper sulfide nanocomposite material comprises the following steps: S1. Dissolve 0.2g carbon nanotubes, 0.2g copper nitrate, 0.5g thiourea, 1g glucose and 0.1mol H3PO4 in a mixture of 60mlL deionized water and 20mL ethylene glycol, stir and mix well, transfer to a hydrothermal reactor, react at 160°C for 24h, and collect the precipitated product by centrifugation after the reaction is completed; S2. calcining and annealing the product obtained in step S1 in a tube furnace at 800° C. for 24 h to obtain a dual-carbon confined phosphorus-doped copper sulfide nanocomposite material.

[0052] The electrochemical testing method of the obtained dual-carbon confined phosphorus-doped copper sulfide nanocomposite material is the same as that of Example 1.

[0053] Example 4 A method for preparing a dual carbon-confined phosphorus-doped copper sulfide nanocomposite material comprises the following steps: S1, dissolve 0.5g carbon nanotubes, 0.5g copper nitrate, 2g thiourea, 2g glucose and 0.2mol H3PO4 in a mixture of 60mlL deionized water and 20mL ethylene glycol, stir and mix well, transfer to a hydrothermal reactor, react at 140°C for 12h, and collect the precipitated product by centrifugation after the reaction is completed; S2. calcining and annealing the product obtained in step S1 in a tube furnace at 900° C. for 12 h to obtain a dual-carbon confined phosphorus-doped copper sulfide nanocomposite material.

[0054] The electrochemical testing method of the obtained dual-carbon confined phosphorus-doped copper sulfide nanocomposite material is the same as that of Example 1.

[0055] Example 5 A method for preparing a dual carbon-confined phosphorus-doped copper sulfide nanocomposite material comprises the following steps: S1. Dissolve 0.8 g carbon nanotubes, 5 g copper sulfate, 1 g thioacetamide, 0.5 g dopamine and 1 mol H3PO4 in a mixture of 60 ml deionized water and 20 mL ethylene glycol, stir and mix well, transfer to a hydrothermal reactor, react at 120°C for 36 h, and collect the precipitated product by centrifugation after the reaction is completed; S2. The product obtained in step S1 is calcined and annealed in a tube furnace at 700° C. for 36 hours to obtain a dual-carbon confined phosphorus-doped copper sulfide nanocomposite material.

[0056] The electrochemical testing method of the obtained dual-carbon confined phosphorus-doped copper sulfide nanocomposite material is the same as that of Example 1.

[0057] Example 6 A method for preparing a dual carbon-confined phosphorus-doped copper sulfide nanocomposite material comprises the following steps: S1. Dissolve 0.6 g carbon nanotubes, 3 g copper chloride, 3 g thiourea, 3 g glucose and 2 mol H3PO4 in a mixture of 60 ml deionized water and 20 mL ethylene glycol, stir and mix well, transfer to a hydrothermal reactor, react at 150°C for 30 h, and collect the precipitated product by centrifugation after the reaction is completed; S2. The product obtained in step S1 is calcined and annealed in a tube furnace at 600° C. for 30 h to obtain a dual-carbon confined phosphorus-doped copper sulfide nanocomposite material.

[0058] The electrochemical testing method of the obtained dual-carbon confined phosphorus-doped copper sulfide nanocomposite material is the same as that of Example 1.

[0059] The invention has a simple preparation process, and the double carbon-confined phosphorus-doped copper sulfide nanocomposite material is used in the negative electrode material of sodium ion batteries. As the negative electrode of sodium ion batteries, the double carbon confinement can effectively buffer the volume change of active materials, improve the performance of sodium ion batteries, and is suitable for industrial production and large-scale use of energy storage. It has certain advantages in the application of negative electrode materials for sodium ion batteries.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A dual carbon-confined phosphorus-doped copper sulfide nanocomposite material, characterized in that: It comprises an inner core, a middle layer of microspheres and an outer shell coating layer; the inner core is a carbon core, the middle layer of microspheres are micron-sized balls formed by phosphorus-doped copper sulfide nanosheet clusters, and the outer shell coating layer is a carbon layer.

2. The dual carbon-confined phosphorus-doped copper sulfide nanocomposite material according to claim 1, characterized in that: The diameter of the micron ball formed by the phosphorus-doped copper sulfide nanosheet cluster is 1-10 μm, and the thickness of the phosphorus-doped copper sulfide nanosheet is 1-100 nm.

3. The dual carbon-confined phosphorus-doped copper sulfide nanocomposite material according to claim 1, characterized in that: The phosphorus-doped copper sulfide nanosheets contain 0.05-0.5 mol of phosphorus element per 1 mol of copper sulfide.

4. The dual carbon-confined phosphorus-doped copper sulfide nanocomposite material according to claim 1, characterized in that: The carbon core is a carbon nanotube, and the carbon layer is amorphous carbon.

5. A method for preparing a dual carbon-confined phosphorus-doped copper sulfide nanocomposite material, characterized in that: The following steps are involved: The carbon nanotubes, copper source, sulfur source, carbon source and phosphorus source are dissolved in an ethylene glycol solution, stirred and mixed evenly, subjected to a hydrothermal reaction, centrifuged and washed, and a precipitated product is collected; The precipitated product is subjected to a calcination reaction to obtain a dual-carbon confined phosphorus-doped copper sulfide nanocomposite material.

6. The method for preparing the dual-carbon confined phosphorus-doped copper sulfide nanocomposite material according to claim 5, characterized in that: The usage ratio of the carbon nanotubes, copper source, sulfur source, carbon source, phosphorus source and ethylene glycol solution is (0.01-1) g: (0.1-5) g: (0.1-5) g: (0.1-5) g: (0.05-5) mol: 80 mL; the ethylene glycol solution is prepared by mixing deionized water and ethylene glycol in a volume ratio of 3:

1.

7. The method for preparing the dual-carbon confined phosphorus-doped copper sulfide nanocomposite material according to claim 5, characterized in that: The temperature of the hydrothermal reaction is 100-180° C., and the time of the hydrothermal reaction is 6-48 h.

8. The method for preparing the dual-carbon confined phosphorus-doped copper sulfide nanocomposite material according to claim 5, characterized in that: The copper source is any one of copper sulfate, copper nitrate and copper chloride; the sulfur source is any one of thiourea and thioacetamide; the carbon source is any one of glucose and dopamine; and the phosphorus source is H3PO4.

9. The method for preparing the dual carbon-confined phosphorus-doped copper sulfide nanocomposite material according to claim 5, characterized in that: The calcination reaction temperature is 500-1000° C. and the calcination reaction time is 6-48 h.

10. Use of the dual-carbon confined phosphorus-doped copper sulfide nanocomposite material according to any one of claims 1 to 4 in the preparation of negative electrode materials for sodium ion batteries.

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