Two-dimensional / three-dimensional composite material, preparation method thereof, and application of two-dimensional / three-dimensional composite material in electrode and rechargeable battery

Abstract

The invention provides a two-dimensional / three-dimensional composite material, a preparation method thereof and an application of the two-dimensional / three-dimensional composite material in an electrode and a rechargeable battery, a copper source, a cobalt source and a sulfur source are uniformly mixed and then subjected to a hydrothermal reaction, and the nano flower-shaped Cu7S4 / CuCo2S4 composite material is obtained. According to the prepared material, the three-dimensional flower-shaped skeleton and two-dimensional nanosheet interwoven multilevel structure can effectively buffer the volume change caused in the repeated intercalation / deintercalation process of magnesium / lithium ions, so that the completeness of the electrode structure is maintained, and the cycling stability is improved. The material is used as a magnesium / lithium mixed dual-ion battery positive electrode, and can be efficiently matched and cooperated with a Mg < 2 + > / Li < + > dual-ion system in an electrolyte, so that breakthrough in electrode process dynamics and interface stability is realized, the activity of electrolyte metal ions is further activated by adding the lithium bis (trifluoromethanesulfonyl) imide auxiliary agent, and the electrolyte performance is improved. And finally, the magnesium / lithium mixed ion battery is endowed with excellent and stable comprehensive electrochemical performance. And the raw materials are low in cost, cheap and easily available.

Description

Technical Field

[0001] This invention belongs to the field of rechargeable batteries, specifically relating to two-dimensional / three-dimensional composite materials and their preparation methods, as well as their applications in electrodes and rechargeable batteries. This invention prepares flower-shaped copper tetrasulfide / cobalt tetrasulfide nanoarray composite materials for use in the preparation of electrodes and magnesium / lithium mixed-ion rechargeable batteries. Background Technology

[0002] Faced with increasingly stringent requirements for energy density, safety, and cost of energy storage systems from electric vehicles and smart grids, the development of next-generation electrochemical energy storage technologies that surpass traditional lithium-ion batteries is imperative. Among numerous candidates, magnesium-ion batteries have attracted considerable attention due to their unique advantages.

[0003] Magnesium resources are abundant in the Earth's crust (approximately 2.1%), far exceeding lithium (approximately 0.0017%), giving it significant cost potential. More importantly, magnesium anodes are less prone to dendrite formation during deposition / dissolution, fundamentally addressing the long-standing safety concerns of lithium metal anodes. Furthermore, magnesium can gain or lose two electrons, resulting in a theoretical volumetric capacity of up to 3833 mAh / cm³. -3 Approximately lithium metal (2062 mAh cm⁻¹) -3 Magnesium's abundance is 1.8 times that of lithium metal batteries, making it possible to develop high-volume energy density batteries. Combined with its safety characteristics, magnesium-ion batteries (MIBs) are highly promising candidates for next-generation energy storage systems and potential alternatives to lithium metal batteries.

[0004] Lithium-ion batteries, however, are inherently limited by flammable electrolytes, high-cost key metals (such as cobalt and lithium), limited potential for energy density improvement, and the safety risks of lithium plating caused by fast charging. These limitations make it difficult to fully meet the comprehensive requirements of next-generation energy storage systems for high safety, high energy density, and sustainable development. This hinders their widespread application. In contrast, the magnesium anode used in MIBs has several advantages, including magnesium (3833 mAh cm⁻¹). -3 Magnesium exhibits a higher volumetric capacity than sodium metal. Furthermore, magnesium is cost-effective, and crucially, the deposition / dissolution of magnesium ions on the magnesium metal surface does not produce dendrites, thus ensuring a high level of safety. To take into account the advantages of LIBs and MIBs, research on constructing Mg / Li hybrid ion batteries (MLHBs) is also increasing; this battery system will rapidly kinetic Li-ion batteries. + Combined with dendrite-free Mg anode.

[0005] To date, cathode materials for MLHBs have been extensively studied. Among them, transition metal sulfides (TMS) are considered promising electrode materials due to their high theoretical capacity, low cost, and phase transition mechanism. Therefore, it is essential to provide a high-performance cathode material for MLHBs. Summary of the Invention

[0006] The purpose of this invention is to provide a two-dimensional / three-dimensional composite material and its preparation method. Using low-cost raw materials, a flower-shaped copper tetrasulfide / copper tetrasulfide nanocomposite is obtained through a one-step hydrothermal method. The preparation method is simple, the product has a novel structure, high yield, and low cost.

[0007] Another objective of this invention is to provide an application of two-dimensional / three-dimensional composite materials in electrodes, using the prepared flower-shaped copper tetrasulfide / cobalt tetrasulfide nanocomposite to prepare electrodes.

[0008] Another objective of this invention is to provide an application of two-dimensional / three-dimensional composite materials in rechargeable batteries. The two-dimensional / three-dimensional composite materials are used as the positive electrode material of magnesium / lithium hybrid ion batteries, and 0.4 M APC-0.4 M LiTFSI is used as the electrolyte to manufacture magnesium / lithium hybrid ion rechargeable batteries, thereby improving the poor cycle stability of magnesium / lithium hybrid ion rechargeable batteries.

[0009] The specific technical solution of this invention is as follows:

[0010] A method for preparing two-dimensional / three-dimensional composite materials, specifically:

[0011] The copper and cobalt sources are mixed in water and stirred. Then, a sulfur source is added, and the mixture is heated and stirred. The resulting solution undergoes a hydrothermal reaction to obtain the final product.

[0012] The molar ratio of the copper source to the cobalt source is 1:1;

[0013] The concentration of the cobalt source in water is 0.094 mol / L;

[0014] The copper source and cobalt source are mixed in water and stirred for 30 minutes;

[0015] The copper source is a soluble copper salt, preferably CuCl2·2H2O;

[0016] The cobalt source is a soluble cobalt salt, preferably CoCl2·6H2O;

[0017] The water is deionized water;

[0018] The concentration of the sulfur source in the water is 1 mol / L;

[0019] The sulfur source is thiourea;

[0020] The heating and stirring process is carried out at 50°C for 10 minutes.

[0021] The hydrothermal reaction is performed at 200-220℃ for 12-13 hours, preferably at 200℃ for 12 hours.

[0022] After the hydrothermal reaction is completed, the product is washed and then dried. The washing consists of 3-5 washes with water and 3-5 washes with ethanol. The drying is carried out at 60-80°C in the air, preferably at 60°C.

[0023] The present invention provides a two-dimensional / three-dimensional composite material, which is prepared by the above method. The two-dimensional / three-dimensional composite material is a flower-shaped copper tetrasulfide / cobalt tetrasulfide copper nickel composite material, which is a flower-shaped structure composed of Cu7S4 / CuCo2S4 nanosheets with a size of 6-8μm.

[0024] This invention prepares a flower-like Cu7S4 / CuCo2S4 composite material. The preparation method utilizes copper salt, cobalt salt, a sulfur source, and deionized water to synthesize the Cu7S4 / CuCo2S4 bimetallic sulfide via hydrothermal synthesis. During the hydrothermal process, water is used as the solvent, providing a mild and controllable reaction environment for the synthesis of the Cu7S4 / CuCo2S4 composite material. This also directly contributes to its unique nano-flower-like hierarchical structure, thereby achieving faster ion diffusion, more active site exposure, and more stable long-cycle performance in the cathode of magnesium / lithium mixed-ion rechargeable batteries.

[0025] This invention provides an application of two-dimensional / three-dimensional composite materials in electrodes, which are used to prepare electrodes as the positive electrode of magnesium / lithium hybrid ion rechargeable batteries.

[0026] This invention provides an application of two-dimensional / three-dimensional composite materials in rechargeable batteries. The positive electrode of a magnesium / lithium mixed-ion rechargeable battery prepared using the two-dimensional / three-dimensional composite material is combined with APC-LiTFSI as the electrolyte to produce a magnesium / lithium mixed-ion rechargeable battery, thereby improving the poor cycle stability of magnesium / lithium mixed-ion rechargeable batteries.

[0027] The preparation method of the APC-LiTFSI electrolyte is as follows:

[0028] S1. Dissolve anhydrous aluminum chloride in tetrahydrofuran and stir;

[0029] S2. Add the phenyl magnesium chloride solution to the solution obtained in step S1 and stir. The resulting electrolyte is an APC electrolyte (all-phenyl complex).

[0030] S3. Add lithium bis(trifluoromethanesulfonyl)imide to the solution obtained in step S2 and stir to obtain the electrolyte APC-LiTFSI.

[0031] The electrolyte is preferably a 0.4 M APC-0.4 M LiTFSI electrolyte.

[0032] In steps S1, S2 and S3, the stirring refers to a stirring speed of 300-800 rpm;

[0033] In step S1, the ratio of anhydrous aluminum chloride to tetrahydrofuran is 0.2667:2-4 g / mL, preferably 0.2667:3 g / mL;

[0034] In step S2, the concentration of the phenyl magnesium chloride solution is 2 M, and the solvent is tetrahydrofuran;

[0035] In step S2, the volume ratio of the phenyl magnesium chloride solution to the volume of tetrahydrofuran in step S1 is 1-3:2-4; preferably 2:3.

[0036] In step S3, the concentration of lithium bis(trifluoromethanesulfonyl)imide in the prepared electrolyte is 0.2-0.6 M, preferably 0.4 M.

[0037] The specific method for assembling and manufacturing magnesium / lithium hybrid ion rechargeable batteries is as follows:

[0038] The prepared two-dimensional / three-dimensional composite material, flower-shaped copper tetrasulfide / cobalt tetrasulfide copper-nickel composite material, was used as the active material. It was mixed uniformly with conductive carbon black and PVDF in a ratio of 8:1:1 or 7:2:1, and then magnetically stirred for 6-8 hours to uniformly disperse it in the PVDF. The prepared slurry was then coated onto copper foil using a coater and placed in a vacuum drying oven at 60-80℃ for 12-24 hours. After drying, it was pressed into sheets using a tablet press and then cut into small circular electrode sheets using a cutting machine. The prepared electrode sheets were assembled into button batteries in a glove box filled with high-purity argon gas and with water and oxygen values ​​≤0.01 ppm. Magnesium foil with a purity of Mg≥99.99% and a thickness of 70 μm was cut into spacer sizes. Copper foil with a purity of Cu≥99.99% and a thickness of 0.5 nm was cut into electrode sheet sizes. The specific method for assembling the battery is as follows: After dripping one drop of electrolyte onto the motor housing, place the electrode plate, then add two drops of electrolyte and place the glass fiber, add three drops of electrolyte onto the glass fiber and place the magnesium sheet as the counter electrode, then place a gasket and a spring sheet, and use an MSK-110 small manual button battery sealing machine to press and seal the battery, and leave it for 6-10 hours.

[0039] The present invention provides a method for preparing flower-like copper 7S4 / Co2S4 bimetallic sulfide nanoflowers by mixing copper and cobalt salts in water, adding thiourea, and performing a one-step hydrothermal reaction. The nanoflowers are assembled from Cu7S4 / Co2S4 composite sulfide nanosheets. The two metals, Cu and Co, form complementary and coupled electronic structures in the sulfide lattice, synergistically optimizing the overall conductivity of the material, enhancing the kinetics of redox reactions, and forming abundant reactive sites, significantly improving electrochemical activity. The Cu7S4 and CuCo2S4 phases are tightly bonded through a heterogeneous interface, constructing a stable composite framework. This structure effectively buffers the volumetric strain caused by ion insertion / extraction during charging and discharging, inhibiting material pulverization and capacity decay, thereby significantly improving cycle stability. The flower-like structure is assembled from two-dimensional nanosheets, forming a three-dimensional open network. This structure not only provides a shorter ion diffusion path, promoting the rapid migration of magnesium / lithium ions, but also enhances the electron conduction network, achieving synergistic and rapid ion and electron transport. The nanoflower structure possesses a large specific surface area, increasing the contact interface between the electrode material and the electrolyte. This facilitates thorough electrolyte wetting and efficient charge transfer, thereby improving the utilization rate of active materials and rate performance. Material systems based on copper and cobalt sulfides exhibit good thermal stability, and copper and cobalt resources are relatively abundant and cost-effective, making them potential for large-scale application. The composite material provided by this invention, through component design and structural regulation, effectively combines the advantages of high conductivity, structural stability, and fast reaction kinetics, demonstrating comprehensive electrochemical performance in magnesium / lithium hybrid ion batteries, including high specific capacity, excellent rate performance, and long cycle life.

[0040] Furthermore, the Li⁺ provided by LiTFSI in the electrolyte can rapidly insert into / extract from the cathode material, significantly improving reaction kinetics and initial capacity; simultaneously, the Mg provided by APC... 2+ Reversible storage can be achieved in materials, Li + With Mg 2+ The synergistic embedding mechanism enables the material to exhibit higher specific capacity and coulombic efficiency than single-ion storage. APC ensures dendrite-free deposition and highly reversible exfoliation of the magnesium anode, while 0.4 M LiTFSI helps form a stable electrode / electrolyte interface (CEI) film on the cathode surface, jointly suppressing side reactions and material dissolution. This results in excellent cycle stability of the composite cathode in mixed ion systems. The electrolyte system has high ionic conductivity and a wide voltage window. Combined with the three-dimensional nanoflower structure of Cu7S4 / CuCo2S4, it can effectively promote the growth of Li... + With Mg 2+The diffusion and electron conduction of these elements endow the material with excellent rate performance. Cu7S4 / CuCo2S4, based on the relatively abundant resources of Cu and Co, has a relatively simple and low-cost synthesis method. It also exhibits good compatibility with the classic APC-LiTFSI dual-salt electrolyte system, demonstrating potential for large-scale application. This material achieves efficient synergistic storage of magnesium / lithium ions in a 0.4M APC-0.4M LiTFSI electrolyte, combining high capacity, excellent cycle stability, and good rate performance. It provides a promising cathode solution for developing safe, low-cost, and high-performance magnesium / lithium hybrid ion batteries.

[0041] In this invention, the nano-hierarchical flower-like composite material has a larger specific surface area than a single spiky structure, enabling it to react with Mg in the electrolyte. 2+ / Li + The efficient adaptation and synergy of the dual-ion system achieves breakthroughs in electrode process kinetics and interfacial stability. The addition of lithium bis(trifluoromethanesulfonyl)imide additive further activates the activity of electrolyte metal ions, ultimately endowing the magnesium / lithium hybrid-ion battery with excellent and stable comprehensive electrochemical performance. The raw materials are inexpensive, and the synthesis method allows for batch control.

[0042] Compared with existing technologies, the multi-level structure of the nanoflower-like Cu7S4 / CuCo2S4 composite material prepared in this invention, with its interwoven three-dimensional flower-like framework and two-dimensional nanosheets, effectively buffers the volume changes caused by repeated insertion / extraction of magnesium / lithium ions, thereby maintaining the integrity of the electrode structure and improving cycle stability. These nanoflowers are assembled from Cu7S4 / CuCo2S4 composite sulfide nanosheets. This significantly increases the specific surface area of ​​the material, exposing abundant redox active sites, which is beneficial for electrolyte wetting and rapid charge transfer, significantly improving electrochemical activity and reaction kinetics. When used as the cathode of a magnesium / lithium hybrid dual-ion battery, this material exhibits high specific capacity, long cycle life, and good rate performance in 0.4 M APC-0.4 M LiTFSI electrolyte, thanks to its unique component synergy and structural advantages. The 0.4 M APC-0.4 M LiTFSI dual-salt electrolyte exhibits low overpotential, a wide electrochemical window, and good magnesium deposition / dissolution reversibility. It forms a stable and compatible electrode / electrolyte interface with the Cu7S4 / CuCo2S4 cathode material, jointly ensuring the long-term cycle stability of the battery. This material is synthesized using abundant copper and cobalt as raw materials via a simple and feasible hydrothermal / solvothermal method. The raw material cost is low, the process is simple, and it has the potential for large-scale production. Attached Figure Description

[0043] Figure 1 SEM image of Cu7S4 / CuCo2S4 prepared in Example 1;

[0044] Figure 2 Here is a high-magnification SEM image of Cu7S4 / CuCo2S4 prepared in Example 1;

[0045] Figure 3 The XRD pattern of Cu7S4 / CuCo2S4 prepared in Example 1;

[0046] Figure 4 The electrolyte prepared in Example 1 was subjected to a current of 0.4 mA cm⁻¹ -2 Testing of Mg||Mg symmetric cells at current density;

[0047] Figure 5 The electrolytes prepared in Examples 1, 2, and 3 were used as cathode materials in magnesium / lithium hybrid ion batteries based on nanoflower-like Cu7S4 / CuCo2S4 materials at a concentration of 0.5 A g. -1 Cyclic stability test results at current density (first at 0.2 A g) -1 (Activation is performed by repeating the cycle 10 times).

[0048] Figure 6 The following are rate performance test results of the electrolytes prepared in Examples 1, 2, and 3 applied to magnesium / lithium hybrid ion batteries based on nanoflower-like Cu7S4 / CuCo2S4 materials as cathode materials;

[0049] Figure 7 To demonstrate the application of the electrolyte prepared in Example 1 to flower-structured CuS materials and nano-flower-structured Cu7S4 / CuCo2S4 materials as cathode materials in magnesium / lithium hybrid ion batteries at 0.5 A g... -1 Cyclic stability test results at current density;

[0050] Figure 8 SEM image of CuS nanomaterials prepared in Comparative Example 1;

[0051] Figure 9 SEM image of CuCo2S4 nanomaterials prepared in Comparative Example 2;

[0052] Figure 10 SEM image of the Cu7S4 / CuCo2S4 composite material prepared in Comparative Example 3;

[0053] Figure 11 SEM image of the Cu7S4 / CuCo2S4 composite material prepared in Comparative Example 4;

[0054] Figure 12 SEM image of the Cu7S4 / CuCo2S4 composite material prepared in Comparative Example 5;

[0055] Figure 13 SEM image of the Cu7S4 / CuCo2S4 composite material prepared in Comparative Example 6;

[0056] Figure 14 SEM image of the Cu7S4 / CuCo2S4 composite material prepared in Comparative Example 7;

[0057] Figure 15 SEM image of the Cu7S4 / CuCo2S4 composite material prepared in Comparative Example 8;

[0058] Figure 16 SEM image of the Cu7S4 / CuCo2S4 composite material prepared in Comparative Example 9;

[0059] Figure 17 SEM image of Cu7S4 / CuCo2S4 composite material prepared for Comparative Example 10. Detailed Implementation

[0060] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0061] Unless otherwise specified, all test materials and reagents used in the following examples are commercially available.

[0062] Unless otherwise specified in the embodiments, the techniques or conditions described in the literature in this field or in accordance with the product manual may be followed.

[0063] Example 1

[0064] A method for preparing a two-dimensional / three-dimensional composite nanoflower-like Cu7S4 / CuCo2S4 composite material includes the following steps:

[0065] 0.8925 g of CoCl₂·6H₂O and 0.64 g of CuCl₂·2H₂O were dissolved in 40 ml of deionized water and stirred for 30 min. Then, 3.05 g of thiourea was added, and the mixture was stirred for 10 min under a 50 °C water bath. The resulting solution was then placed in a 50 ml Teflon-lined autoclave and kept at 200 °C for 12 h. The resulting Cu₇S₄ / CuCo₂S₄ sample was washed three times with water and three times with ethanol, and then dried under vacuum at 60 °C. The obtained SEM images are shown below. Figure 1 and Figure 2 As shown, the sample structure is clearly a nanoflower structure, with a size of approximately 6-8 μm. XRD patterns are as follows. Figure 3As shown, its characteristic peaks perfectly correspond to the standard card number PDF#33-0489 for Cu7S4 and the standard card number PDF#42-1450 for CuCo2S4.

[0066] Example 1 also prepared a 0.4 M APC-0.4 M LiTFSI electrolyte, the preparation method of which includes the following steps:

[0067] 0.2667 g of anhydrous aluminum chloride (AlCl3, 99%, Aladdin) was dissolved in 3 mL of tetrahydrofuran (THF, Aladdin) solvent, and stirred vigorously at 800 rpm for 12 h. Then, 2 mL of 2 M phenyl magnesium chloride solution (in tetrahydrofuran solvent) was added dropwise to the solution, and the mixture was stirred magnetically at 800 rpm for 12 h to obtain Mg. 2+ / Li + Mix the electrolyte. Finally, dissolve 0.574 g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI, 99.9%, Aladdin) in the above Mg... 2+ / Li + The mixed electrolyte was stirred at 800 rpm for 12 h to obtain a 0.4 M APC-0.4 M LiTFSI electrolyte.

[0068] Example 2

[0069] A method for preparing a two-dimensional / three-dimensional composite nanoflower-like Cu7S4 / CuCo2S4 composite material, which is carried out exactly according to Example 1.

[0070] Example 2 also describes a method for preparing a 0.4M APC-0.2M LiTFSI electrolyte, comprising the following steps:

[0071] 0.2667 g of anhydrous aluminum chloride (AlCl3, 99%, Aladdin) was dissolved in 3 mL of tetrahydrofuran (THF, Aladdin) solvent, and stirred vigorously at 800 rpm for 12 h. Then, 2 mL of 2 M phenyl magnesium chloride solution (in tetrahydrofuran solvent) was added dropwise to the solution, and the mixture was stirred magnetically for 12 h to obtain Mg. 2+ / Li + Mix the electrolyte. Finally, dissolve 0.287 g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI, 99.9%, Aladdin) in the above Mg... 2+ / Li + The mixed electrolyte was stirred for 12 h to obtain a 0.4 M APC-0.2 M LiTFSI electrolyte.

[0072] Example 3

[0073] A method for preparing a two-dimensional / three-dimensional composite nanoflower-like Cu7S4 / CuCo2S4 composite material, which is carried out exactly according to Example 1.

[0074] Example 3 also describes a method for preparing a 0.4M APC-0.6M LiTFSI electrolyte, comprising the following steps:

[0075] 0.2667 g of anhydrous aluminum chloride (AlCl3, 99%, Aladdin) was dissolved in 3 mL of tetrahydrofuran (THF, Aladdin) solvent, and stirred vigorously at 800 rpm for 12 h. Then, 2 mL of 2 M phenyl magnesium chloride solution (in tetrahydrofuran solvent) was added dropwise to the solution, and the mixture was stirred magnetically for 12 h to obtain Mg. 2+ / Li + Mix the electrolyte. Finally, dissolve 0.861 g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI, 99.9%, Aladdin) in the above Mg... 2+ / Li + The mixed electrolyte was stirred for 12 h to obtain a 0.4 M APC-0.6 M LiTFSI electrolyte.

[0076] Comparative Example 1 (as a comparison)

[0077] A method for preparing CuS nanomaterials includes the following steps:

[0078] 0.64 g CuCl₂·2H₂O was dissolved in 40 ml of water and stirred for 30 min. Then, 3.05 g thiourea was added, and the mixture was stirred for 10 min under a 50 °C water bath. The resulting solution was then placed in a 50 ml Teflon-lined autoclave and kept at 200 °C for 12 h. The obtained CuS sample was washed three times with water and three times with ethanol, and then dried under vacuum at 60 °C. The obtained SEM image is shown below. Figure 8 As shown, the sample structure is clearly a nanosphere structure. When only copper chloride is added, the selective adsorption and regulation of the crystal face by cobalt ions are lacking, and the crystal growth tends to be isotropic. At the same time, the morphology guiding ability of thiourea is weakened, resulting in the product changing from nanoflowers to thermodynamically more stable spherical particles.

[0079] Comparative Example 2

[0080] A method for preparing CuCo2S4 nanomaterials includes the following steps:

[0081] 0.64 g CuCl₂·2H₂O and 1.42 g CoCl₂·6H₂O were dissolved in 40 ml of water and stirred for 30 min. Then, 3.05 g thiourea was added, and the mixture was stirred for 10 min under a 50 °C water bath. The resulting solution was then placed in a 50 ml Teflon-lined autoclave and kept at 200 °C for 12 h. The obtained CuCo₂S₄ sample was washed three times with water and three times with ethanol, and then dried under vacuum at 60 °C. The obtained SEM images are shown below. Figure 9 As shown, the sample structure is clearly a clustered structure composed of nanosheets. This is because excess cobalt ions accelerate nucleation, neutralize the surface charge of the nanosheets, and disrupt the morphological guidance of thiourea, causing the nanosheets to stack randomly into blocky aggregates, unable to assemble into an orderly flower-like structure.

[0082] Comparative Example 3

[0083] A method for preparing a Cu7S4 / CuCo2S4 composite material includes the following steps: dissolving 1.785g CoCl2·6H2O and 0.64g CuCl2·2H2O in 40ml of water, stirring for 30min, then adding 3.05g thiourea, stirring for 10min under a 50℃ water bath, and then placing the resulting solution in a 50ml Teflon-lined autoclave and maintaining it at 200℃ for 12h. The obtained Cu7S4 / CuCo2S4 sample is washed three times with water and three times with ethanol; then dried under vacuum at 60℃. The SEM image of the product is shown below. Figure 10 As shown, the overall morphology remains that of nanoflowers, but these are bouquets of nanospheres. Excessive cobalt ion concentration significantly increases the nucleation rate, generating a large number of crystal nuclei instantaneously. This leads to rapid consumption of raw materials in subsequent growth stages, leaving insufficient time for the crystals to preferentially grow along specific crystal planes. This results in the formation of isotropic spherical particles rather than the anisotropic "flower-like" structure that requires slow growth control. High concentrations also reduce the ion diffusion gradient, hindering the formation of flower-like branching structures that radiate outwards from the center.

[0084] Comparative Example 4

[0085] A method for preparing a Cu7S4 / CuCo2S4 composite material includes the following steps: dissolving 0.8925g CoCl2·6H2O and 1.28g CuCl2·2H2O in 40ml of water, stirring for 30min, then adding 3.05g thiourea, stirring for 10min under a 50℃ water bath, and then placing the resulting solution in a 50ml Teflon-lined autoclave and maintaining it at 200℃ for 12h. The obtained Cu7S4 / CuCo2S4 sample is washed three times with water and three times with ethanol; then dried under vacuum at 60℃. The SEM image of the product is shown below. Figure 11As shown, the structure largely remains nanosheet-like, without forming nanoflowers. Excess copper ions dominate the formation of layered copper-rich sulfide phases, while the doping and assembly regulation of diluted cobalt confines growth to a two-dimensional plane, ultimately resulting in thick nanosheets rather than three-dimensional nanoflowers.

[0086] Comparative Example 5

[0087] A method for preparing a Cu7S4 / CuCo2S4 composite material includes the following steps: dissolving 0.8925 g of CoCl2·6H2O and 0.64 g of CuCl2·2H2O in 40 ml of water, stirring for 30 min, then adding 6.1 g of thiourea, stirring for 10 min under a water bath at 50 °C, and then placing the resulting solution in a 50 ml Teflon-lined autoclave and maintaining it at 200 °C for 12 h. The obtained Cu7S4 / CuCo2S4 sample is washed three times with water and three times with ethanol; then dried under vacuum at 60 °C. The SEM image of the product is shown below. Figure 12 As shown, the nanosphere morphology is largely maintained. Excessive thiourea leads to rapid release of sulfur ions, resulting in excessively high supersaturation and accelerating isotropic nucleation and growth. Simultaneously, the uniform adsorption of excessive thiourea on the crystal face weakens its ability to guide anisotropic growth, causing the crystals to tend towards forming spherical particles with the lowest surface energy.

[0088] Comparative Example 6

[0089] A method for preparing a Cu7S4 / CuCo2S4 composite material includes the following steps:

[0090] 0.8925 g of CoCl₂·6H₂O and 0.64 g of CuCl₂·2H₂O were dissolved in 40 ml of water and stirred for 30 min. Then, 3.05 g of thiourea was added, and the mixture was stirred for 10 min under a water bath at 50 °C. The resulting solution was then placed in a 50 ml Teflon-lined autoclave and kept at 160 °C for 12 h. The obtained Cu₇S₄ / CuCo₂S₄ sample was washed three times with water and three times with ethanol, and then dried under vacuum at 60 °C. The SEM image of the product is shown below. Figure 13 As shown, the nano-flower morphology is largely maintained, although the flowers are somewhat broken. This is because when the temperature drops to 160℃, the thermodynamic driving force and kinetic rate of the reaction system decrease, the decomposition of thiourea and ion diffusion slow down, and the sulfur ion (S... 2- Limited release and metal ion migration slow crystal growth, preventing nanosheets from fully dissolving, recrystallizing, and assembling in an orderly manner; weakened anisotropic growth results in rough edges and loose stacking of petal structures, making it difficult to form clear and sharp lamellar structures; the crystallinity of the product may decrease, leading to a "soft and collapsed" overall morphology that is not regular enough.

[0091] Comparative Example 7

[0092] A method for preparing a nanoflower-like Cu7S4 / CuCo2S4 composite material includes the following steps:

[0093] 0.8925 g of CoCl₂·6H₂O and 0.64 g of CuCl₂·2H₂O were dissolved in 40 ml of water and stirred for 30 min. Then, 3.05 g of thiourea was added, and the mixture was stirred for 10 min under a water bath at 50 °C. The resulting solution was then placed in a 50 ml Teflon-lined autoclave and kept at 180 °C for 12 h. The obtained Cu₇S₄ / CuCo₂S₄ sample was washed three times with water and three times with ethanol, and then dried under vacuum at 60 °C. The SEM image of the product is shown below. Figure 14 As shown, the crystals generally maintain a spherical morphology with nano-spiky surfaces. When the temperature is lowered to 180℃, the decomposition and ion diffusion rates of thiourea slow down, resulting in insufficient supersaturation of the reaction system. Anisotropic growth is inhibited, and the crystals tend to form spherical structures with lower surface energy. At the same time, the unevenness of local sulfur ion release or surface adsorption causes secondary growth of nano-spiky structures on the surface of the spheres, reducing the overall morphological regularity.

[0094] Comparative Example 8

[0095] A method for preparing a Cu7S4 / CuCo2S4 composite material includes the following steps:

[0096] 0.8925 g of CoCl₂·6H₂O and 0.64 g of CuCl₂·2H₂O were dissolved in 40 ml of water and stirred for 30 min. Then, 3.05 g of thiourea was added, and the mixture was stirred for 10 min under a water bath at 50 °C. The resulting solution was then placed in a 50 ml Teflon-lined autoclave and kept at 200 °C for 8 h. The obtained Cu₇S₄ / CuCo₂S₄ sample was washed three times with water and three times with ethanol, and then dried under vacuum at 60 °C. The SEM image of the product is shown below. Figure 15 As shown, the nanosphere structure is largely maintained. Although the reaction time was shortened from 12h to 8h, the key growth stage was terminated prematurely, resulting in insufficient thiourea decomposition and ion release, insufficient sulfur ion supply in the later stages, and the inability of the crystals to continue anisotropic growth. The Oswald ripening process was incomplete, and the particles failed to be fully reconstructed and the surface smoothed. The time for directional assembly of nanosheets was insufficient, and the sheet-like units did not have time to stack in an orderly manner into a regular three-dimensional flower shape, but only initially aggregated into rough spheres. The crystallinity may be low, resulting in a rough particle surface and loose morphology. The "unattractive" appearance is actually an intermediate state in which the morphological evolution is not complete.

[0097] Comparative Example 9

[0098] A method for preparing a Cu7S4 / CuCo2S4 composite material includes the following steps:

[0099] 0.8925 g of CoCl₂·6H₂O and 0.64 g of CuCl₂·H₂O were dissolved in 40 ml of water and stirred for 30 min. Then, 3.05 g of thiourea was added, and the mixture was stirred for 10 min under a water bath at 50 °C. The resulting solution was then placed in a 50 ml Teflon-lined autoclave and kept at 200 °C for 10 h. The obtained Cu₇S₄ / CuCo₂S₄ sample was washed three times with water and three times with ethanol, and then dried under vacuum at 60 °C. The SEM image of the product is shown below. Figure 16 As shown, the nanospheres are largely retained, although their surfaces are somewhat rough. When the reaction time is shortened from 12 hours to 10 hours, the complete process of crystal growth and assembly is affected. The decomposition of thiourea and the release of metal ions are not yet fully saturated, resulting in insufficient anisotropic growth momentum. At the same time, the directional attachment and Oswald ripening process of the nanosheets are prematurely interrupted, resulting in incomplete and fine assembly of the three-dimensional flower-like structure. Due to the insufficient growth period, the petal structure is still loose and the edges are not clear enough. The overall regularity and crystallinity are not as good as the complete and beautiful nanoflowers obtained after 12 hours.

[0100] Comparative Example 10

[0101] A method for preparing a nanoflower-like Cu7S4 / CuCo2S4 composite material includes the following steps:

[0102] 0.8925 g of CoCl₂·6H₂O and 0.64 g of CuCl₂·H₂O were dissolved in 40 ml of water and stirred for 30 min. Then, 3.05 g of thiourea was added, and the mixture was stirred for 10 min under a water bath at 50 °C. The resulting solution was then placed in a 50 ml Teflon-lined autoclave and kept at 200 °C for 14 h. The obtained Cu₇S₄ / CuCo₂S₄ sample was washed three times with water and three times with ethanol, and then dried under vacuum at 60 °C. The SEM image of the product is shown below. Figure 17 As shown, the nanoflowers largely remained intact. However, extending the time to 14 hours caused the nanosheets to overgrow and stack, resulting in a crowded petal structure and weakened layering. This ultimately destroyed the graceful and orderly aesthetic morphology formed under the 12-hour condition.

[0103] The application of nano-flower-like Cu7S4 / CuCo2S4 composite material as the positive electrode active material of magnesium / lithium hybrid ion battery and 0.4 M APC-0.4 M LiTFSI as a novel electrolyte for magnesium / lithium hybrid ion battery are described in the following process:

[0104] The nano-flower-like Cu7S4 / CuCo2S4 composite material obtained in Example 1 was mixed with conductive carbon black and PVDF in a mass ratio of 7:2:1. After being uniformly dispersed in PVDF by magnetic stirring for 6 hours, the prepared slurry was coated onto copper foil using a coater and placed in a vacuum drying oven at 80°C for 12 hours. After drying, it was pressed into tablets using a tablet press and then cut into small circular electrode sheets using a cutting machine.

[0105] The prepared electrode sheets were assembled into button cells in a glove box filled with high-purity argon gas and where the water and oxygen levels were both ≤0.01 ppm. Magnesium foil with a purity of Mg ≥ 99.99% and a thickness of 70 μm was cut to the size of a spacer. Copper foil with a purity of Cu ≥ 99.99% and a thickness of 0.5 nm was cut to the size of an electrode sheet. The specific assembly method was as follows: one drop of electrolyte was placed on the motor housing, followed by the electrode sheet; then two drops of electrolyte were added, followed by glass fiber; three drops of electrolyte were added to the glass fiber, followed by the magnesium sheet as the counter electrode; then a spacer and a spring sheet were placed in the center; and the battery was pressed and sealed using an MSK-110 small manual button cell sealing machine and left to stand for 10 hours.

[0106] Specific testing procedure: After assembling the magnesium-lithium dual-ion half-cell, the following steps were set on the Xinwei tester: first, constant current discharge to 0.01V, then constant current charging to 2V, repeating this cycle a certain number of times. The electrolyte used in battery assembly was prepared in Example 1.

[0107] The test results and data are as follows:

[0108] Figure 4 The Mg||Mg symmetric cell test using 0.4 M APC-0.4 M LiTFSI electrolyte demonstrates that 0.4 M APC-0.4 M LiCl, as a magnesium / lithium hybrid ion battery electrolyte, exhibits low overpotential and long-term cycling stability, indicating that uniform deposition and extraction of magnesium has minimal nucleation barriers.

[0109] Figure 5 Electrolytes of 0.4 M APC-0.2 M LiTFSI, 0.4 M APC-0.4 M LiTFSI, and 0.4 M APC-0.6 M LiTFSI were used as cathode materials for magnesium / lithium hybrid ion batteries prepared in Example 1, employing nanoflower-like Cu7S4 / CuCo2S4 composite materials at a concentration of 0.5 A g. -1 (First at 0.2 A g) -1 (Activation was performed after 10 cycles), and the cycling stability test graph at current density showed that after 50 cycles, the specific capacity of the battery using 0.4 M APC-0.4 M LiTFSI as the electrolyte remained at 301 mAh g⁻¹. -1The specific capacities of batteries using 0.4 M APC-0.2 M LiTFSI and 0.4 M APC-0.6 M LiTFSI as electrolytes remained at 211 and 132 mAh g, respectively. -1 .

[0110] Figure 6 The electrolytes prepared in Examples 1, 2, and 3 were used as cathode materials for magnesium / lithium hybrid ion batteries in the nanoflower-like Cu7S4 / CuCo2S4 composite material prepared in Example 1, initially at 0.2 A g. -1 Activation was performed for 10 cycles at current densities of 0.4, 0.6, 0.8, and 1 A g. -1 Rate performance test results at current density. At the second rate gradient, the specific capacity corresponding to the 0.4 M APC-0.4 M LiTFSI electrolyte is 508 mAh g⁻¹. -1 (0.4A g) -1 ), 471 mAh g -1 (0.6A g -1 ), 412mAhg -1 (0.8A g -1 ), 239 mAhg -1 (1 A g -1 Both have higher specific capacities than APC-0.2 M LiTFSI and APC-0.6 M LiTFSI.

[0111] Figure 7 An electrolyte of 0.4 M APC-0.4 M LiTFSI was used as a cathode material for magnesium / lithium hybrid batteries in CuS nanomaterials and nanoflower-like Cu7S4 / CuCo2S4 materials at a concentration of 0.5 A g. -1 The chart shows a comparison of cycling stability at this current density. After 50 cycles at this current density, the specific capacity of CuS can only be maintained at 46 mAhg. -1 Its performance is inferior to that of Cu7S4 / CuCo2S4 materials.

[0112] The combination of the nano-flower-like Cu7S4 / CuCo2S4 cathode material prepared in this invention with a 0.4 mol / L APC–0.4 mol / L LiTFSI electrolyte fully leverages the advantages of its high specific surface area, abundant porosity, and numerous active sites in its two-dimensional / three-dimensional composite structure. At the same time, thanks to the low overpotential and high stability of the electrolyte, the cycle performance, energy density, and rate performance of the battery are significantly improved. This makes it one of the ideal cathode / electrolyte combinations for high-performance lithium-magnesium dual-ion batteries.

[0113] The above description of the embodiments is intended to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for preparing a two-dimensional / three-dimensional composite material, characterized in that, The preparation method is specifically as follows: The copper and cobalt sources are mixed in water and stirred. Then, a sulfur source is added, and the mixture is heated and stirred. The resulting solution undergoes a hydrothermal reaction to obtain the final product.

2. The preparation method according to claim 1, characterized in that, The molar ratio of the copper source to the cobalt source is 1:

1.

3. The preparation method according to claim 1, characterized in that, The concentration of the cobalt source in water is 0.094 mol / L.

4. The preparation method according to claim 1 or 3, characterized in that, The concentration of the sulfur source in the water is 1 mol / L.

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

6. The preparation method according to claim 1, characterized in that, The hydrothermal reaction conditions are 200-220℃ for 12-13 hours.

7. A two-dimensional / three-dimensional composite material prepared by the preparation method according to any one of claims 1-6, characterized in that, The two-dimensional / three-dimensional composite material is a flower-shaped copper tetrasulfide / cobalt tetrasulfide copper nickel composite material, which is a flower-shaped structure composed of Cu7S4 / CuCo2S4 nanosheets with a size of 6-8μm.

8. The application of the two-dimensional / three-dimensional composite material of claim 7 in an electrode, characterized in that, Electrodes were fabricated using two-dimensional / three-dimensional composite materials and used as the positive electrode of a magnesium / lithium hybrid ion rechargeable battery.

9. The application of the two-dimensional / three-dimensional composite material of claim 7 in a rechargeable battery, characterized in that, A positive electrode for a magnesium / lithium hybrid ion rechargeable battery, prepared using two-dimensional / three-dimensional composite materials, is used in conjunction with APC-LiTFSI as the electrolyte to fabricate a magnesium / lithium hybrid ion rechargeable battery.

10. The application according to claim 9, characterized in that, The APC-LiTFSI electrolyte is a 0.4 M APC-0.4 M LiTFSI electrolyte.

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