Copper sulfide / copper ferrous disulfide composite material, preparation method and application thereof, and rechargeable battery

Abstract

The invention provides a copper sulfide / copper ferrous disulfide composite material, a preparation method and application thereof and a rechargeable battery, a copper source, an iron source and a sulfur source are ultrasonically dispersed in an organic solvent and stirred, a solvothermal reaction is carried out, and flower-shaped CuS / CuFeS2 is obtained. Compared with the prior art, the preparation method is high in yield and low in cost. The CuS / CuFeS2 combined composite material is very novel when being applied to the sodium ion battery, and is combined application for the first time; according to the CuS / CuFeS2 composite material, the high theoretical capacity of CuS and the stable structure advantage of CuFeS2 are combined, the electron / ion transmission path can be optimized through the synergistic effect of the two sulfides, the internal resistance is reduced, and the overall efficiency of the battery is further improved; the flower-shaped structure has a relatively large specific surface area, so that shuttling of sodium ions is facilitated. The product is used as a sodium-ion battery negative electrode material and has relatively large specific capacity and relatively good cycle performance.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of rechargeable batteries, and particularly relates to a copper sulfide / copper disulfide composite material and a preparation method and application thereof, and a rechargeable battery, wherein the prepared binary metal sulfide CuS / CuFeS2 is used as an anode material of a sodium ion battery to manufacture the rechargeable battery. BACKGROUND

[0002] In view of the increase of environmental pollution and energy consumption, electrochemical energy storage as a technology with high energy conversion efficiency has been widely concerned. In the past few decades, lithium ion batteries have been the dominant storage device as the most successful energy storage device, especially in the field of portable electronic devices and electric vehicles. However, the limited availability and uneven geographical distribution of lithium resources lead to rising costs, causing concerns about its long-term sustainability and economic feasibility.

[0003] Sodium is very abundant in nature and is evenly distributed, showing a similar "rocking chair" electrochemical mechanism as lithium ion batteries, and is considered a promising complementary material. Therefore, sodium ion batteries are a viable, economically efficient and long-term energy storage alternative, which can accompany the transition from fossil energy to renewable energy and show great potential in future applications.

[0004] In recent years, metal sulfide materials have attracted much attention in the field of energy due to their unique structural characteristics. Such materials not only have abundant electrochemically active sites, but also exhibit ideal electronic band structures and excellent mechanical strength, while also having excellent thermal stability. These outstanding physical and chemical properties make them a potential research hotspot in the fields of energy storage and catalysis. Metal sulfide (MS x ) is a kind of negative electrode material for SIB, which has similar properties to metal oxide (MO s ). Compared with M-O bond in MO s , M-S bond is weaker, which is beneficial to the conversion reaction in the charging and discharging process in dynamics. Metal sulfide shows great potential as a negative electrode material for SIB system due to its high theoretical capacity based on conversion reaction, higher conductivity than metal oxide type, moderate reaction platform and low cost. Although metal sulfide has many advantages in sodium storage, there are still many intractable problems that hinder its commercial application. For example, the intrinsic conductivity of most metal sulfides is low, which restricts the charge transfer efficiency, resulting in poor rate performance and serious capacity decay under high current density.

[0005] Therefore, how to improve the performance of metal sulfide materials used in sodium ion batteries is a problem to be solved. SUMMARY

[0006] The application aims to provide a copper sulfide / copper ferrous disulfide composite material and a preparation method thereof, and the copper sulfide / copper ferrous disulfide composite material is synthesized by a solvothermal reaction of a mixed solution with copper salt and iron salt as raw materials.

[0007] The application further aims to provide an application of the copper sulfide / copper ferrous disulfide composite material, and the application is to prepare a sodium ion battery anode as an active material, and then to prepare a rechargeable battery.

[0008] The application further aims to provide a rechargeable battery prepared by using the sodium ion battery anode prepared by using the copper sulfide / copper ferrous disulfide composite material as an active material.

[0009] The application specifically provides the following technical scheme:

[0010] The application specifically provides the following technical scheme:

[0011] The copper source, the iron source and the sulfur source are dispersed in an organic solvent and uniformly mixed, and then a solvothermal reaction is performed, and after the reaction is completed, the flower-like CuS / CuFeS2 is obtained through centrifugation, washing and drying.

[0012] The molar ratio of the copper source, the iron source and the thiourea is 0.5-1:1:2-3, and preferably 1:1:2.18;

[0013] The copper source is preferably a divalent copper salt, and preferably copper chloride dihydrate; the iron source is a trivalent iron salt, and preferably ferric chloride hexahydrate; the organic solvent is ethylene glycol; the sulfur source is thiourea; the use amount ratio of the copper source and the organic solvent is 0.00625-0.0375 mol·L -1 , and preferably 0.0125 mol·L -1 ; the use amount ratio of the iron source and the organic solvent is 0.00625-0.0375 mol·L -1 ; and preferably 0.0125 mol·L -1 .

[0014] The solvothermal reaction is performed at 180-200 DEG C for 12 hours, and preferably at 200 DEG C for 12 hours, and the solvothermal reaction is performed in a polytetrafluoroethylene reactor in a closed reaction mode.

[0015] The final product is obtained by a one-step solvothermal method, the one-step solvothermal method has a simple preparation process, mild reaction conditions and excellent product performance. 2+ , Fe 3+The 3D flower-like microspheres can be self-assembled from thiourea by adjusting the reaction temperature and the proportion of the dosage to grow directionally. The solvent is ethylene glycol. In the initial stage of the solvothermal reaction, the copper ions and iron ions in the solution combine with the sulfur ions generated by the decomposition of thiourea to form copper sulfide, copper disulfide and other crystal nuclei. These crystal nuclei are the starting point of crystal growth. Ethylene glycol as a solvent promotes the uniform dispersion of the crystal nuclei under solvothermal conditions based on its suitable steric hindrance volume effect, and guarantees the excellent dispersibility of the subsequent growth of nanomaterials. After the formation of the crystal nuclei, the ions around the crystal nuclei continue to diffuse and deposit on the surface of the crystal nuclei, so that the crystal gradually grows. Due to the anisotropy of crystal growth, nanosheet structures grow in a specific crystal face direction. With the progress of the reaction, the nanosheets continue to grow and thicken. The nanosheets grown to a certain extent begin to connect and assemble with each other, arrange radially around a center, and finally form a flower-like structure. During the solvothermal reaction process, the reactants are fully mixed and uniformly reacted in the solution, so that the chemical composition uniformity of the final product is good, and the two phases (CuS and CuFeS2) are in close contact to form a heterojunction. The traditional method needs to synthesize CuS and CuFeS2 separately and then composite, while the one-step solvothermal method can directly obtain the target composite by adjusting the precursor proportion (Cu / Fe / S molar ratio) and temperature. In the high-temperature and high-pressure solvothermal environment, the metal salt and thiourea are hydrolyzed to release metal ions and sulfur ions. When the ion concentration exceeds the critical saturation, a large number of micron crystal nuclei are formed instantaneously. From the mechanism, the core advantage of the one-step solvothermal method for synthesizing CuS / CuFeS2 flower-like structure lies in the in-situ heterostructure construction and self-assembly synergistic regulation. Compared with the step-by-step synthesis method, this process avoids the problem of phase separation and realizes the integrated regulation of components and morphology. From the perspective of reaction kinetics, the one-step solvothermal method exhibits the rate control advantage of time and space coordination. In space, it shows uniformity. The solvothermal reaction is carried out in a sealed reaction kettle, and the reaction solution is uniformly mixed in the whole space, so that the components can uniformly contact and react in space, which avoids the uneven reaction rate caused by local concentration difference and is conducive to the formation of uniform morphology and structure of the product in space. In time, it shows controllability. By accurately controlling the temperature and time of the solvothermal reaction, the reaction rate and process can be precisely controlled. Under suitable temperature and time conditions, the reaction can proceed according to the expected path, so that the processes of crystal growth, nucleation and other processes are orderly carried out in time, realizing the accurate control of the components and morphology of the product, and embodying the rate control advantage of time and space coordination. It makes the reaction proceed at a relatively stable rate, and the concentration change of various substances in the reaction system is continuous, which is conducive to the formation of a single-phase product.

[0016] The final product presents a flower-like structure, which not only significantly increases the specific surface area and accelerates the electrolyte penetration, but also ensures that the active substances inside the electrode fully participate in the reaction and can relieve the volume expansion, thereby improving the cycle stability of the battery.

[0017] The application provides a copper sulfide / copper ferrous disulfide composite material prepared by the method, the copper sulfide / copper ferrous disulfide composite material is a micron flower formed by a crosslinked nanosheet network, the thickness of the nanosheet is 6-8 nm, and the size of the micron flower is 5-6 microns.

[0018] The CuS / CuFeS2 composite material combines the high theoretical capacity of CuS and the stable structure advantage of CuFeS2, can significantly improve the specific capacity and energy density of the electrode material. CuS provides rich active sites to promote multi-electron reactions, while the stable framework of CuFeS2 effectively alleviates the volume expansion during the charging and discharging process, reduces the structure collapse, thereby enhancing the cycle stability and rate performance of the battery.

[0019] The application provides application of the copper sulfide / copper ferrous disulfide composite material, which is used as an active substance to prepare a sodium ion battery anode.

[0020] The application provides a rechargeable battery, which is prepared by using the sodium ion battery anode prepared by using the copper sulfide / copper ferrous disulfide composite material as an active substance.

[0021] The specific application method is as follows:

[0022] The copper sulfide / copper ferrous disulfide composite material prepared above is mixed with conductive carbon black and PVDF in a ratio of 8:1:1 or 7:2:1, and then NMP is added dropwise, and the mixture is uniformly dispersed in the NMP by magnetic stirring for 6-8 hours, and the uniformly mixed slurry is coated on a copper foil using a coater, and then placed in a vacuum drying oven at 60-80 DEG C, dried for 12-24 hours, and then pressed into a sheet using a sheet press, and then cut into a small circular electrode sheet using a sheet cutter; the prepared electrode sheet is assembled into a button cell in a glove box filled with high-purity argon gas and having a water oxygen value of less than or equal to 0.01 ppm; and the electrolyte is NaPF6+DEGDME, the purity of the sodium sheet is Na≥99.99%, the thickness is 0.5 mm, and the sodium sheet is cut into an electrode sheet size after rolling.

[0023] The specific method for assembling the battery is as follows: 1 drop of electrolyte is added to the positive electrode shell, and then the electrode sheet is placed, 1 drop of electrolyte is added, and then the glass fiber is placed, 3 drops of electrolyte are added to the glass fiber, and then the sodium sheet is placed as a counter electrode, followed by placing two pieces of nickel foam, and then adding 4 drops of electrolyte, covering the negative electrode shell, and then tightly sealing the battery using a hydraulic machine, and then placing for 6-12 hours.

[0024] Metal sulfides have high stability compared to single metal sulfides due to multiple metal valence states, bimetallic synergistic reaction behavior, relatively short electron transfer pathways, and enhanced electron conduction capacity, and therefore exhibit excellent electrochemical performance. CuS exhibits high theoretical capacity, good electronic conductivity, low cost, and environmental friendliness as a sodium ion battery electrode material. However, it also has problems of serious volume expansion and slow reaction kinetics. The addition of CuFeS2 forms a composite material, and the mixed metal sulfide enhances ion conductivity, provides more redox reaction sites, and further improves capacity. The use of a bimetallic sulfide material form and the effective design of the microstructure of the material can synergistically improve the conductivity, structural stability, and active site density of the material, thereby significantly enhancing the energy storage capacity, rate performance, and cycle life.

[0025] The copper sulfide / copper ferrous disulfide composite material prepared in the application exhibits a capacity of 520 mAh g -1 at a current density of 1 Ag -1high specific capacity, stable cycle performance. It is shown that CuS / CuFeS2 is an excellent and promising sodium-ion anode material. The composite material is synthesized by a simple solvothermal reaction. The flower-like structure has a high specific surface area and porous characteristics, which can increase the contact area of the electrode and the electrolyte, promote ion / electron transmission, and thus improve the capacity, rate performance and cycle stability of the battery. The unique hierarchical structure can alleviate the volume expansion during charging and discharging, reduce material pulverization, and its open pores (interlamellar gap pores) are beneficial to electrolyte penetration, further prolonging the battery life and maintaining high energy output. Micro-sized materials usually have a tighter crystal structure and higher mechanical strength, which can effectively alleviate the volume expansion and stress change during charging and discharging, reduce the pulverization or cracking of the electrode material, thereby significantly improving the cycle stability and service life of the battery. Metal sulfides usually have high theoretical specific capacity and energy density due to their multi-electron redox reaction characteristics, which are much higher than traditional oxide electrode materials, which helps to improve the overall energy storage performance of the battery.

[0026] Compared with the prior art, the CuS / CuFeS2 prepared by the present application is micron flower-like, with a size of about 5-6 microns, and provides a preparation method of nanomaterials with high yield and low cost. The composite material of CuS / CuFeS2 is novel in application in sodium-ion batteries, and is applied for the first time. The prepared composite material has a flower-like structure, has a large specific surface area due to the flower-like structure, is beneficial to the shuttling of sodium ions, has stable performance and is not easy to be oxidized by air, and can be stored for a long time. The prepared composite material has a large specific capacity and good cycle performance when used as a sodium-ion battery anode material. The cross-linked nanosheet network of the prepared composite material can effectively buffer volume changes and has abundant active sites, improving the service life, capacity and cycle stability of the battery, and solving the technical problems of poor cycle stability of electrode materials. The raw materials of the present application are low in price, the synthesis process is simple, and batch production can be carried out. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 SEM image of CuS / CuFeS2 micron flower prepared in Example 1;

[0028] Figure 2 XRD image of CuS / CuFeS2 micron flower prepared in Example 1;

[0029] Figure 3 TEM image of CuS / CuFeS2 micron flower prepared in Example 1 (for nanosheet);

[0030] Figure 4TEM image (overall) of CuS / CuFeS2 microflower prepared for Example 1;

[0031] Figure 5 Transmission Mapping image of CuS / CuFeS2 microflower prepared for Example 1;

[0032] Figure 6 HRTEM image of CuS / CuFeS2 microflower prepared for Example 1;

[0033] Figure 7 SEM image of CuS / CuFeS2 composite prepared for Example 2;

[0034] Figure 8 SEM image of CuS / CuFeS2 composite prepared for Example 3;

[0035] Figure 9 SEM image of CuS / CuFeS2 composite prepared for Example 4;

[0036] Figure 10 SEM image of CuS / CuFeS2 composite prepared for Example 5;

[0037] Figure 11 SEM image of CuS / CuFeS2 composite prepared for Example 6;

[0038] Figure 12 SEM image of CuS / CuFeS2 composite prepared for Example 7;

[0039] Figure 13 SEM image of CuS / CuFeS2 composite prepared for Example 8;

[0040] Figure 14 SEM image of CuS / CuFeS2 composite prepared for Example 9;

[0041] Figure 15 SEM image of CuS / CuFeS2 composite prepared for Example 10;

[0042] Figure 16 SEM image of CuS / CuFeS2 composite prepared for Example 11;

[0043] Figure 17 SEM image of CuS prepared for Example 12;

[0044] Figure 18 SEM image of CuFeS2 prepared for Example 13;

[0045] Figure 19CuS / CuFeS2 micro-flower material prepared for Example 1 as a sodium-ion battery negative electrode material at 0.2 Ag -1 The cycle performance test graph at a current density of 0.2 Ag

[0046] Figure 20 CuS / CuFeS2 micro-flower material prepared for Example 1 as a sodium-ion battery negative electrode material at 0.2 Ag -1 The charge-discharge curve performance test graph at a current density of 0.2 Ag

[0047] Figure 21 CuS / CuFeS2 micro-flower material prepared for Example 1 as a sodium-ion battery negative electrode material at 1 Ag -1 The cycle performance test graph at a current density of 1 Ag

[0048] Figure 22 CuS / CuFeS2 micro-flower material prepared for Example 1 as a sodium-ion battery negative electrode material at 1 Ag -1 The charge-discharge curve performance test graph at a current density of 1 Ag

[0049] Figure 23 The rate performance test graph of CuS / CuFeS2 micro-flower material prepared for Example 1 as a sodium-ion battery negative electrode material at different current densities

[0050] Figure 24 CuS material prepared for Example 12 as a sodium-ion battery negative electrode material at 0.2 Ag -1 The cycle performance test graph at a current density of 0.2 Ag

[0051] Figure 25 CuFeS2 material prepared for Example 13 as a sodium-ion battery negative electrode material at 0.2 Ag -1 The cycle performance test graph at a current density of 0.2 Ag DETAILED DESCRIPTION

[0052] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described below in connection with the embodiments of the present application. Obviously, the described embodiments are only some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0053] In the following examples, the test materials and reagents used, unless otherwise specified, can be obtained from commercial channels.

[0054] The specific techniques or conditions not specified in the examples can be carried out according to the techniques or conditions described in the literature in the field or according to the product instructions.

[0055] Example 1

[0056] A method for preparing a copper sulfide / copper ferrous disulfide composite material, comprising the following steps:

[0057] 0.166 g of thiourea was dispersed in 80 mL of ethylene glycol to form a uniform solution. 0.27 g of FeCl3·6H2O and 0.17 g of CuCl2·2H2O were weighed and added to the uniformly dispersed solution, and stirring was continued at room temperature for 1 h. Then it was transferred to a 50 mL polytetrafluoroethylene reactor, and placed in an oven at 200℃ for 12 h. It was naturally cooled to room temperature, and the product was washed with deionized water by centrifugation 4 times, washed with ethanol 2 times, and vacuum dried at 60℃ for 12 h to obtain a copper sulfide / copper ferrous disulfide composite material. The SEM image thereof is shown in Figure 1 As can be seen from the figure, it is a micron flower structure with a size of 5-6 μm. The XRD pattern of the CuS / CuFeS2 composite material obtained in this example is shown in Figure 2 , which proves that the obtained product is CuS / CuFeS2. The TEM image of the CuS / CuFeS2 composite material obtained in this example is shown in Figure 3 and Figure 4 , which proves that the material obtained is a micron flower morphology, and the size of the nanosheet is 7 nm. The transmission Mapping is shown in Figure 5 , which can prove that the element distribution in the material is relatively uniform. The HRTEM image thereof is shown in Figure 6 , which proves the existence of two single substances in the composite material by the lattice fringes.

[0058] Example 2 (as a comparison)

[0059] A method for preparing a copper sulfide / copper ferrous disulfide composite material, comprising the following steps:

[0060] 0.166 g of thiourea was dispersed in 80 mL of ethylene glycol to form a uniform solution. 0.27 g of FeCl3·6H2O and 0.17 g of CuCl2·2H2O were weighed and added to the uniformly dispersed solution, and stirring was continued at room temperature for 1 h. Then it was transferred to a 50 mL polytetrafluoroethylene reactor, and placed in an oven at 120℃ for 12 h. It was naturally cooled to room temperature, and the product was washed with deionized water by centrifugation 4 times, washed with ethanol 2 times, and vacuum dried at 60℃ for 12 h. The SEM image thereof is shown in Figure 7 As can be seen, when the composite material of Example 2 is synthesized, the solvent temperature is lower, and the nanoflower cannot be aggregated to form a flower sheet structure.

[0061] Example 3 (as a comparison)

[0062] A method of preparing a copper sulfide / copper ferrous disulfide composite material, comprising the steps of:

[0063] 0.166 g of thiourea was dispersed in 80 mL of ethylene glycol to form a uniform solution. 0.27 g of FeCl3-6H2O and 0.17 g of CuCl2-2H2O were weighed and added to the uniformly dispersed solution, and stirring was continued at room temperature for 1 h. Subsequently, it was transferred to a 50 mL polytetrafluoroethylene reactor, and placed in an oven at 140 °C for 12 h. It was naturally cooled to room temperature, washed with deionized water by centrifugation 4 times, washed with ethanol 2 times, and vacuum dried at 60 °C for 12 h. The SEM image thereof is shown in FIG. 4, and it can be seen that a blocky structure is formed. Figure 8

[0064] Example 4 (as a comparison)

[0065] A method of preparing a copper sulfide / copper ferrous disulfide composite material, comprising the steps of:

[0066] 0.166 g of thiourea was dispersed in 80 mL of ethylene glycol to form a uniform solution. 0.27 g of FeCl3-6H2O and 0.17 g of CuCl2-2H2O were weighed and added to the uniformly dispersed solution, and stirring was continued at room temperature for 1 h. Subsequently, it was transferred to a 50 mL polytetrafluoroethylene reactor, and placed in an oven at 160 °C for 12 h. It was naturally cooled to room temperature, washed with deionized H2O by centrifugation 4 times, washed with ethanol 2 times, and vacuum dried at 60 °C for 12 h. The SEM image thereof is shown in FIG. 5, and it can be seen that a partial flaky structure has been formed. Figure 9

[0067] Example 5

[0068] A method of preparing a copper sulfide / copper ferrous disulfide composite material, comprising the steps of:

[0069] 0.166 g of thiourea was dispersed in 80 mL of ethylene glycol to form a uniform solution. 0.27 g of FeCl3-6H2O and 0.17 g of CuCl2-2H2O were weighed and added to the uniformly dispersed solution, and stirring was continued at room temperature for 1 h. Subsequently, it was transferred to a 50 mL polytetrafluoroethylene reactor, and placed in an oven at 180 °C for 12 h. It was naturally cooled to room temperature, washed with deionized H2O by centrifugation 4 times, washed with ethanol 2 times, and vacuum dried at 60 °C for 12 h. The SEM image thereof is shown in FIG. 6, and it can be seen that a partial flaky structure has formed a flower-like structure, but the flaky structure has not completely aggregated into a flower-like structure due to the insufficient temperature. Figure 10

[0070] Example 6

[0071] A method of preparing a copper sulfide / copper ferrous disulfide composite material, comprising the steps of:​​​

[0072] 0.166 g thiourea was dispersed in 80 mL ethylene glycol to form a homogeneous solution. 0.27 g FeCl3-6H2O and 0.085 g CuCl2-2H2O were weighed and added to the homogeneously dispersed solution and continued to stir for 1 h at room temperature. Then transferred to a 50 mL Teflon reactor and placed in an oven at 200 °C for 12 h. Naturally cooled to room temperature, washed with deionized H2O by centrifugation for 4 times, washed with ethanol for 2 times, and vacuum dried at 60 °C for 12 h. The SEM image is shown in Figure 1. Figure 11 It can be seen that there are flower-like structures but there are many fragments because the Cu source is too little to completely react.

[0073] Example 7 (as a comparison)

[0074] A method for preparing a copper sulfide / copper ferrous disulfide composite material, comprising the following steps:

[0075] 0.166 g thiourea was dispersed in 80 mL ethylene glycol to form a homogeneous solution. 0.27 g FeCl3-6H2O and 0.085 g CuCl2-2H2O were weighed and added to the homogeneously dispersed solution and continued to stir for 1 h at room temperature. Then transferred to a 50 mL Teflon reactor and placed in an oven at 200 °C for 12 h. Naturally cooled to room temperature, washed with deionized H2O by centrifugation for 4 times, washed with ethanol for 2 times, and vacuum dried at 60 °C for 12 h. The SEM image is shown in Figure 1. Figure 12 It can be seen that there are flower-like structures but there are many fragments because the Cu source is too little to completely react.

[0076] Example 8 (as a comparison)

[0077] A method for preparing a copper sulfide / copper ferrous disulfide composite material, comprising the following steps:

[0078] 0.166 g thiourea was dispersed in 80 mL ethylene glycol to form a homogeneous solution. 0.27 g FeCl3-6H2O and 0.085 g CuCl2-2H2O were weighed and added to the homogeneously dispersed solution and continued to stir for 1 h at room temperature. Then transferred to a 50 mL Teflon reactor and placed in an oven at 200 °C for 12 h. Naturally cooled to room temperature, washed with deionized H2O by centrifugation for 4 times, washed with ethanol for 2 times, and vacuum dried at 60 °C for 12 h. The SEM image is shown in Figure 1. Figure 13 It can be seen that there are flower-like structures but there are many fragments because the Cu source is too little to completely react.

[0079] Example 9 (as a comparison)

[0080] A method for preparing a copper sulfide / copper ferrous disulfide composite material, comprising the following steps:

[0081] A solution of 0.166 g thiourea was dispersed in 80 mL ethylene glycol to form a uniform solution. 0.54 g FeCl3-6H2O and 0.17 g CuCl2-2H2O were weighed and added to the uniformly dispersed solution, and stirring was continued at room temperature for 1 h. Subsequently, it was transferred to a 50 mL polytetrafluoroethylene reactor, and placed in an oven at 200 °C for 12 h. It was naturally cooled to room temperature, washed by centrifugation with deionized H2O four times, washed with ethanol twice, and vacuum dried at 60 °C for 12 h. Its SEM image is shown in FIG. 6, which shows obvious flaky structure, but is not uniform and has not been assembled into a flower shape. Figure 14 The flaky structure cannot be agglomerated into a flower-shaped material due to the lack of Fe source.

[0082] Example 10 (as a comparison)

[0083] A method for preparing a copper sulfide / copper ferrous sulfide composite material, comprising the following steps:

[0084] A solution of 0.166 g thiourea was dispersed in 80 mL ethylene glycol to form a uniform solution. 0.54 g FeCl3-6H2O and 0.17 g CuCl2-2H2O were weighed and added to the uniformly dispersed solution, and stirring was continued at room temperature for 1 h. Subsequently, it was transferred to a 50 mL polytetrafluoroethylene reactor, and placed in an oven at 200 °C for 12 h. It was naturally cooled to room temperature, washed by centrifugation with deionized H2O four times, washed with ethanol twice, and vacuum dried at 60 °C for 12 h. Its SEM image is shown in FIG. 6, which shows obvious flaky structure, but is not uniform and has not been assembled into a flower shape. Figure 15

[0085] Example 11 (as a comparison)

[0086] A method for preparing a copper sulfide / copper ferrous sulfide composite material, comprising the following steps:

[0087] A solution of 0.166 g thiourea was dispersed in 80 mL ethylene glycol to form a uniform solution. 0.54 g FeCl3-6H2O and 0.17 g CuCl2-2H2O were weighed and added to the uniformly dispersed solution, and stirring was continued at room temperature for 1 h. Subsequently, it was transferred to a 50 mL polytetrafluoroethylene reactor, and placed in an oven at 200 °C for 12 h. It was naturally cooled to room temperature, washed by centrifugation with deionized H2O four times, washed with ethanol twice, and vacuum dried at 60 °C for 12 h. Its SEM image is shown in FIG. 6, which shows obvious flaky structure, but is not uniform and has not been assembled into a flower shape. Figure 16

[0088] Example 12 (as a comparison)

[0089] A method for preparing a CuS material, comprising the following steps:

[0090] ​​0.166 g thiourea was dispersed in 80 mL ethylene glycol to form a uniform solution. 0.27 g FeCl3·6H2O was weighed and added to the uniformly dispersed solution, and stirring was continued at room temperature for 1 h. Subsequently, it was transferred to a 50 mL polytetrafluoroethylene reactor, and placed in an oven at 200°C for 12 h. It was naturally cooled to room temperature, washed by centrifugation with deionized H2O four times, washed with ethanol twice, and vacuum dried at 60°C for 12 h. The SEM image thereof is shown in Fig. 6, and it can be seen that part of the flower-like structure is present, but most of them are in the form of broken pieces. Figure 17 It can be seen that the broken piece-like structure does not present a flower shape.

[0091] Example 13 (as a comparison)

[0092] A method for preparing a CuFeS2 material, comprising the following steps:

[0093] 0.166 g thiourea was dispersed in 80 mL ethylene glycol to form a uniform solution. 0.27 g FeCl3·6H2O was weighed and added to the uniformly dispersed solution, and stirring was continued at room temperature for 1 h. Subsequently, it was transferred to a 50 mL polytetrafluoroethylene reactor, and placed in an oven at 200°C for 12 h. It was naturally cooled to room temperature, washed by centrifugation with deionized H2O four times, washed with ethanol twice, and vacuum dried at 60°C for 12 h. The SEM image thereof is shown in Fig. 6, and it can be seen that part of the flower-like structure is present, but most of them are in the form of broken pieces. Figure 18 It can be seen that the broken piece-like structure does not present a flower shape.

[0094] Example 14

[0095] An application of a copper sulfide / ferrous disulfide copper composite material as an active material for preparing a sodium ion battery anode, and further preparing a rechargeable battery, specifically as follows:

[0096] The CuS / CuFeS2 micro-flower structure material prepared in Example 1 was used as an active material, and was uniformly mixed with conductive carbon black and PVDF at a ratio of 8:1:1. NMP was added dropwise, and the mixture was uniformly dispersed in it by magnetic stirring for 8 hours. The uniformly mixed slurry was coated on a copper foil using a coater, and was placed in a vacuum drying oven at 80°C. After drying for 24 hours, it was pressed using a tablet press, and was cut into a small circular electrode sheet using a sheet cutting machine. The prepared electrode sheet was assembled into a button cell in a glove box filled with high-purity argon gas and having a water and oxygen value of ≤0.01 ppm. The electrolyte was NaPF6+DEGDME, the purity of the sodium sheet was Na≥99.99%, and the thickness was 0.5 mm. After rolling and cutting, the electrode sheet was obtained.

[0097] The method for assembling the battery is as follows: 1 drop of electrolyte is added on the positive shell of the battery, and then the electrode sheet is placed; 1 drop of electrolyte is added on the glass fiber, and then the sodium sheet is placed as the counter electrode; 3 drops of electrolyte are added on the glass fiber, and then two pieces of nickel foam are placed; 4 drops of electrolyte are added, the negative shell is covered, the battery is tightly sealed by using a hydraulic machine, and is placed for 12 hours.

[0098] The cycle performance and charge-discharge performance of the button cell are then tested at a current of 0.2 A and 1 A, and the results are shown in Figure 19 、 Figure 20 、 Figure 21 、 Figure 22 . Figure 19 and Figure 20 are the performance tests at a current of 0.2 A g -1 , and still have a capacity of 611 mAh g -1 after 100 cycles, and the coulombic efficiency is always kept at 99%. Figure 21 and Figure 22 are the performance tests at a current of 1.0 A g -1 , and still have a capacity of 520 mAh g -1 after 1000 cycles, and the coulombic efficiency is kept at 99%. As can be seen from the figure, there is a relatively stable charge-discharge platform and cycle performance. The cycle performance at different current densities is also tested, as shown in Figure 23 , the rate performance at different current densities of 0.5, 1, 3, 5 and 10 A g -1 is tested, and it is found that the reversibility is high and the cycle performance can be kept stable after the initial current is cycled at different currents.

[0099] The CuS material prepared in Example 12 is used as the active material, and a button cell is assembled in the same manner as in Example 14, and then the cycle performance of the button cell is tested at a current of 0.2 A, and the results are shown in Figure 24 . As can be seen from the figure, the cycle performance is poor, and the capacity is only 285 mAh g -1 after 50 cycles.

[0100] The CuFeS2 material prepared in Example 13 is used as the active material, and a button cell is assembled in the same manner as in Example 14, and then the cycle performance of the button cell is tested at a current of 0.2 A, and the results are shown in Figure 25 . As can be seen from the figure, the cycle capacity is high but the cycle number is short, and the capacity is 518 mAh g -1 after 30 cycles.

[0101] The present application prepares the final product CuS / CuFeS2 micrometer flower structure composite material by one-step solvothermal method. The flower structure can provide abundant active sites and large specific surface area due to the unique hierarchical porous structure, which is beneficial to electrolyte penetration and ion / electron rapid transmission; the open micrometer flower morphology can effectively relieve the volume strain in the charge / discharge process, and improve the structural stability. Meanwhile, the synergistic effect of CuS and CuFeS2 can optimize the charge distribution and enhance the electrochemical reaction kinetics. This structure also has high theoretical capacity and good cycle performance, exhibits high specific capacity and rate performance in sodium ion batteries, and can be controllably synthesized by simple solvothermal method, which has the potential for large-scale application.

[0102] The above description of the embodiments is to enable those skilled in the art to understand and use the present application. Those skilled in the art can easily make various modifications to the embodiments, and apply the general principles described herein to other embodiments without creative labor. Therefore, the present application is not limited to the above embodiments, and the improvements and modifications made by those skilled in the art without departing from the scope of the present application should be within the protection scope of the present application.

Claims

1. A method for preparing a copper sulfide / ferrous disulfide copper composite material, characterized in that: The preparation method is specifically as follows: The copper source, iron source and sulfur source are dispersed in an organic solvent and mixed, and a solvothermal reaction is carried out. After the reaction is completed, the flower-like CuS / CuFeS2 is obtained by centrifugation, washing and drying.

2. The preparation method according to claim 1, characterized in that The molar ratio of the copper source, the iron source and the thiourea is 0.5-1:1:2-3.

3. The preparation method according to claim 1 or 2, characterized in that The organic solvent is ethylene glycol.

4. The preparation method according to claim 1 or 2, characterized in that The sulfur source is thiourea.

5. The preparation method according to claim 1 or 2, characterized in that The usage ratio of the copper source and the organic solvent is 0.00625-0.0375 mol·L -1 .

6. The preparation method according to claim 1 or 2, characterized in that The solvent thermal reaction is carried out at 180-200° C. for 12 hours.

7. A copper sulfide / ferrous disulfide copper composite material, prepared by the preparation method according to any one of claims 1 to 6, wherein the copper sulfide / ferrous disulfide copper composite material is in the shape of a micron flower composed of a cross-linked nanosheet network, the nanosheet thickness is 6-8 nm, and the size of the micron flower is 5-6 μm.

8. An application of the copper sulfide / ferrous disulfide copper composite material according to claim 7, characterized in that: The copper sulfide / ferrous disulfide copper composite material is used as an active material to prepare a sodium ion battery anode.

9. A rechargeable battery, characterized in that: Made using the sodium ion battery anode according to claim 8.

Images