A cuprous sulfide-nickel disulfide positive electrode material based on two-dimensional nanosheet wrapping three-dimensional cubes and a preparation method and lithium-magnesium dual-ion battery thereof

Abstract

The application provides a kind of copper sulfide@nickel disulfide positive electrode material based on two-dimensional nanosheet wrapping three-dimensional cube and its preparation method and lithium-magnesium dual-ion battery, first using copper salt, alkaline solution and D (+) -glucose in the water bath condition of 70 DEG C, directional formation Cu2O cube.And then, Cu2O and nickel source, sulfur source and surfactant are synthesized by solvothermal synthesis, forming the structure of two-dimensional and three-dimensional combination of NiS2 nanosheet wrapping Cu2S cube.The two-dimensional and three-dimensional combination structure can shorten the particle transmission path, achieve the effect of fast charging and discharging, at the same time, provide more active sites, increase the specific surface area, fully contact with electrolyte, improve the cycle stability of battery.

Description

Technical Field

[0001] This invention belongs to the field of cathode material technology for lithium-magnesium dual-ion batteries, specifically relating to a copper sulfide@nickel disulfide (Cu2S@NiS2) cathode material based on two-dimensional nanosheets encapsulating a three-dimensional cube, its preparation method, and a lithium-magnesium dual-ion battery. The electrolyte used is a 0.4M APC-0.4M LiCl electrolyte. Background Technology

[0002] With the continuous development of the new energy industry, the demand for energy storage materials is constantly increasing. Among them, lithium-ion batteries (LIBs) are widely used in many fields due to their high capacity, high potential, and long lifespan, especially in new energy vehicles, electronic devices, and the military industry. However, due to issues such as lithium resource shortages, high costs, and safety concerns, scientists are continuing to explore alternatives to lithium-ion batteries.

[0003] In recent years, magnesium-ion batteries (MIBs) have gained popularity due to their low cost, safety (no dendrite formation during charging and discharging), and high volumetric capacity (3832 mAh cm⁻¹). -1 It has received widespread attention due to its advantages such as Mg. However, Mg 2+ It exhibits a strong polarization effect, suppressing ion diffusion in solid materials. To leverage the advantages of both LIBs and MIBs, research on constructing Mg / Li hybrid ion batteries (MLHBs) is increasing. This battery system will rapidly integrate Li... + Combined with dendrite-free Mg anode.

[0004] To date, cathode materials for MLHBs have been extensively studied. Among them, transition metal sulfides (TMCs) 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

[0005] The purpose of this invention is to provide a copper sulfide@nickel disulfide cathode material based on two-dimensional nanosheets encapsulating three-dimensional cubes and its preparation method. Cu2O cubes are prepared using inexpensive raw materials, and Cu2S@NiS2 composites with two-dimensional nanosheets encapsulating three-dimensional cubes are obtained by a one-step solvothermal method. The preparation method is simple, and the product has a novel structure, high yield, and low cost.

[0006] Another objective of this invention is to provide a lithium-magnesium dual-ion battery that utilizes a copper sulfide@nickel disulfide cathode material based on two-dimensional nanosheets encapsulating a three-dimensional cube as the electrode material and 0.4M PAPC-0.4M LiCl as the electrolyte, thereby improving the poor cycle stability of lithium-magnesium dual-ion batteries.

[0007] The specific technical solution of this invention is as follows:

[0008] A method for preparing a cuprous sulfide@nickel disulfide cathode material based on two-dimensional nanosheets encapsulating a three-dimensional cube includes the following steps:

[0009] 1) Preparation of Cu₂O cubes;

[0010] 2) Cu2O cubes, nickel source, sulfur source and surfactant are mixed in an organic solvent and subjected to solvothermal treatment to obtain Cu2S@NiS2.

[0011] In step 1), the method for preparing Cu2O cubes is as follows: disperse the copper source in water, add an alkaline solution dropwise, stir, add a reducing agent, and heat to react, thus obtaining the product.

[0012] In step 1), the molar ratio of copper source, alkali and reducing agent in alkaline solution is 1:5-7:0.2-0.4;

[0013] In step 1), the copper source is a soluble copper salt, preferably Cu(CH3COO)2·H2O;

[0014] In step 1), the alkaline solution is a NaOH solution with a concentration range of 4–8 M, preferably 6 M;

[0015] In step 1), the reducing agent is (D+)-glucose;

[0016] In step 1), the concentration of the copper source in the water is 0.2-0.4 mol / L;

[0017] In step 1), the water is deionized water;

[0018] In step 1), the reducing agent is added after stirring, the stirring speed is 300-800 rpm, and the stirring time is 5 minutes;

[0019] In step 1), the heating reaction refers to being carried out in a water bath at 70°C for 1 hour; the entire process in step 1) is carried out under the condition of a water bath at 70°C.

[0020] In step 2), the mass ratio of the Cu2O cube to the nickel source ranges from 2:1 to 1:2, with 1:2 being preferred;

[0021] In step 2), the mass ratio of the nickel source, sulfur source, and surfactant is 4:3-5:60-80;

[0022] In step 2), the nickel source is Ni(NO3)2·6H2O, the sulfur source is thioacetamide (TAA), and the surfactant is polyvinylpyrrolidone (PVP, average molecular weight 8000, K16-18).

[0023] In step 2), the concentration of the nickel source in the organic solvent is 0.01-0.02 mol / L;

[0024] In step 2), the organic solvent is ethylene glycol;

[0025] In step 2), the solvothermal reaction conditions are 160-200℃ for 18-24 hours, preferably 200℃ for 18 hours.

[0026] This invention provides a cuprous sulfide@nickel disulfide cathode material based on two-dimensional nanosheets encapsulating a three-dimensional cube, which is prepared using the method described above. The cuprous sulfide@nickel disulfide cathode material based on two-dimensional nanosheets encapsulating a three-dimensional cube has a size of 4-6 μm, wherein Cu2S is the core and NiS2 is the shell; the outer NiS2 nanosheets have a thickness of 70±5 nm for each layer.

[0027] This invention prepares a Cu2S@NiS2 material with two-dimensional nanosheets encapsulating three-dimensional cubes. In the preparation process, Cu2O cubes are first directionally formed using copper salt, alkaline solution, and D(+)-glucose in a 70°C water bath. Then, Cu2O, a nickel source, a sulfur source, and a surfactant are synthesized as a Cu2S@NiS2 bimetallic sulfide via solvothermal reaction. During the solvothermal process, the organic solvent ethylene glycol serves as the reaction solvent, providing a good homogeneous reaction environment for the reactants, allowing for sufficient contact between reactant molecules. Simultaneously, during crystallization, the surfactant polyvinylpyrrolidone (PVP) adsorbs onto the crystal nucleus surface, and ethylene glycol also adsorbs onto the crystal nucleus to a certain extent. The combined effect of these two substances alters the growth rate and direction of the crystal nucleus. PVP influences crystallization through steric hindrance, while ethylene glycol utilizes its interactions with Cu2O and the nickel source (such as hydrogen bonding) to regulate the growth, ultimately forming a combined two-dimensional and three-dimensional structure of NiS2 nanosheets encapsulating Cu2S cubes. The combination of two-dimensional and three-dimensional structures can shorten the particle transport path, achieving rapid charging and discharging, while providing more active sites, increasing specific surface area, ensuring full contact with the electrolyte, and improving battery cycle stability.

[0028] This invention provides a lithium-magnesium dual-ion battery that utilizes a copper sulfide@nickel disulfide cathode material based on two-dimensional nanosheets encapsulating a three-dimensional cube as the electrode material, and 0.4M APC-0.4M LiCl as the electrolyte, thereby improving the poor cycle stability of lithium-magnesium dual-ion batteries. Specifically, the lithium-magnesium dual-ion battery includes a cathode material prepared using a copper sulfide@nickel disulfide cathode material based on two-dimensional nanosheets encapsulating a three-dimensional cube as the active material.

[0029] The lithium-magnesium dual-ion battery also includes an electrolyte, which is an APC-LiCl electrolyte, preferably a 0.4M MAPC-0.4M LiCl electrolyte.

[0030] The preparation method of the APC-LiCl electrolyte is as follows:

[0031] S1. Dissolve anhydrous aluminum chloride in tetrahydrofuran and stir;

[0032] S2. Add the phenyl magnesium chloride solution to the solution obtained in step S1 and stir. The resulting electrolyte is a (all-phenyl complex) APC electrolyte.

[0033] S3. Add anhydrous lithium chloride to the solution obtained in step S2 and stir to obtain the electrolyte APC-LiCl.

[0034] In steps S1, S2 and S3, the stirring refers to a stirring speed of 300 to 800 rpm;

[0035] In step S1, the ratio of anhydrous aluminum chloride to tetrahydrofuran is 0.2667:2-4 g / mL, preferably 0.2667:3 g / mL;

[0036] In step S2, the concentration of the phenyl magnesium chloride solution is 2M, and the solvent is tetrahydrofuran;

[0037] 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.

[0038] In step S3, the concentration of anhydrous lithium chloride in the prepared electrolyte is 0.2–0.6 M, preferably 0.4 M.

[0039] The specific method for assembling the battery is as follows:

[0040] A copper sulfide@nickel disulfide cathode material, based on two-dimensional nanosheets encapsulating a three-dimensional cube, was mixed with conductive carbon black and PVDF in a ratio of 8:1:1 or 7:2:1. The mixture was then magnetically stirred for 6–8 hours to uniformly disperse the slurry in the PVDF. The prepared slurry was then coated onto copper foil using a coater and dried in a vacuum drying oven at 60–80°C for 12–24 hours. After drying, the foil 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 then assembled into button batteries in a glove box filled with high-purity argon gas and with water and oxygen levels ≤0.01ppm. 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 to 10 hours.

[0041] The present invention provides a method for preparing Cu2S@NiS2 material based on two-dimensional nanosheets encapsulating three-dimensional cubes. Freshly prepared copper hydroxide is synthesized using copper salt and sodium hydroxide as raw materials, and then Cu2O is synthesized by oxidizing glucose using copper hydroxide. Subsequently, Cu2O is mixed with a nickel source, TAA, and PVP in ethylene glycol, and Cu2S@NiS2 bimetallic sulfide is obtained in a one-step solvothermal process. As a non-toxic and low-cost material, Cu2S not only exhibits better thermal stability than many Cu-S compounds (CuS, Cu9S5, Cu7S4, etc.), but is also a highly conductive material (~104 S cm⁻¹). -1 However, Cu2S exhibits unstable cycling performance. To address this, this invention grows NiS2 nanosheets on its surface. The synergistic effect of the two different metals improves the electron transport performance of the material, effectively shortening ion and electron transport paths. Simultaneously, it significantly mitigates volume changes during charge and discharge, increasing battery capacity and enhancing battery stability. Furthermore, the interaction between different metal elements and the unique structure of the bimetallic sulfide create abundant redox reaction active sites. These active sites enhance the interaction between the electrode material and the electrolyte, promoting charge transfer and ion diffusion, thus improving the battery's electrochemical performance. In addition, the 0.4MAPC-0.4M LiCl electrolyte exhibits good stability and low overpotential, enabling reversible magnesium deposition and stripping. The appropriate concentration of LiCl in the electrolyte reacts with the Cu2S@NiS2 cathode material during battery charge and discharge, resulting in a Li+-Li ... +The insertion and extraction of Cu2S@NiS2 materials provide excellent capacity and exhibit good cycling performance. Furthermore, Cu2S@NiS2 materials have advantages such as simple preparation methods and low cost.

[0042] Compared with existing technologies, the Cu2S@NiS2 material prepared by this invention has a stable structure, and the organic combination of two-dimensional and three-dimensional structures can effectively alleviate the volume changes caused by charging and discharging. The NiS2 nanosheets on the outside of the prepared Cu2S@NiS2 material can provide more active sites, increase the specific surface area, and improve cycle performance. When used as a cathode material for lithium-magnesium dual-ion batteries, the prepared Cu2S@NiS2 material has high specific capacity, excellent cycle life, and good rate performance. When used with 0.4M APC-0.4M LiCl electrolyte as a lithium-magnesium dual-ion battery electrolyte, it has low overpotential and long-term cycle stability. Moreover, the raw materials of this invention are inexpensive, the synthesis process is simple, and it can be mass-produced. Attached Figure Description

[0043] Figure 1 SEM image of Cu2O prepared in Example 1;

[0044] Figure 2 SEM image (enlarged view) of Cu2O prepared in Example 1;

[0045] Figure 3 This is a low-magnification SEM image of Cu2S@NiS2 prepared in Example 1;

[0046] Figure 4 Here is a high-magnification SEM image of Cu2S@NiS2 prepared in Example 1;

[0047] Figure 5 TEM image of Cu2S@NiS2 prepared in Example 1;

[0048] Figure 6 TEM image (another field of view) of Cu2S@NiS2 prepared in Example 1;

[0049] Figure 7 The XRD pattern of Cu2O prepared in Example 1;

[0050] Figure 8 The XRD pattern of Cu2S@NiS2 prepared in Example 1;

[0051] Figure 9 SEM image of Cu2S@NiS2 prepared in Comparative Example 1;

[0052] Figure 10 SEM image of Cu2S@NiS2 / Cu prepared in Comparative Example 2;

[0053] Figure 11 SEM image of Cu2S@NiS2 prepared in Comparative Example 3;

[0054] Figure 12 XRD pattern of Cu2S@NiS2 / Cu prepared in Comparative Example 2;

[0055] Figure 13 SEM image of Cu2S prepared in Comparative Example 4;

[0056] Figure 14 The electrolytes prepared in Examples 1, 2, and 3 were subjected to a current of 0.4 mA / cm². -2 Testing of Mg||Mg symmetric cells at current density;

[0057] Figure 15 The electrolytes prepared in Examples 1, 2, and 3 were used as cathode materials for lithium-magnesium dual-ion batteries based on Cu2S@NiS2 material encapsulated in two-dimensional nanosheets at a concentration of 0.3 Ag. -1 Cyclic stability test results at current density;

[0058] Figure 16 The electrolytes prepared in Examples 1, 2, and 3 were used as cathode materials for lithium-magnesium dual-ion batteries based on Cu2S@NiS2 material encapsulated in two-dimensional nanosheets at a concentration of 0.5 Ag. -1 Cyclic stability test results at current density (first at 0.2Ag) -1 (Activation is performed by cycling 10 times in the next cycle);

[0059] Figure 17 The rate performance test results of the electrolytes prepared in Examples 1, 2 and 3 applied to Cu2S@NiS2 material based on two-dimensional nanosheets encapsulating three-dimensional cubes as positive electrode material for lithium magnesium dual-ion batteries are shown in the figure.

[0060] Figure 18 To demonstrate the application of the electrolyte prepared in Example 3 as a positive electrode material for a cubic Cu2S material in a lithium-magnesium dual-ion battery, a study was conducted using 0.1 Ag... -1 Cyclic stability test results at current density;

[0061] Figure 19 To demonstrate the application of the electrolyte prepared in Example 3 as a positive electrode material for a cubic Cu2S material in a lithium-magnesium dual-ion battery at a concentration of 0.3 Ag... -1 Cyclic stability test results at current density;

[0062] Figure 20 The electrolytes prepared in Examples 1, 2, and 3 were used as cathode materials for lithium-magnesium dual-ion batteries based on Cu2S@NiS2 material encapsulated in two-dimensional nanosheets at a concentration of 0.2 Ag. -1Impedance test after 50 cycles at the current density;

[0063] Figure 21 for Figure 20 Enlarged view of the dashed box;

[0064] Figure 22 The N2 adsorption-desorption isotherm of Cu2S@NiS2;

[0065] Figure 23 The corresponding pore size distribution of Cu2S@NiS2. Detailed Implementation

[0066] 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.

[0067] Unless otherwise specified, all test materials and reagents used in the following examples are commercially available.

[0068] 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.

[0069] Example 1

[0070] A method for preparing a cuprous sulfide@nickel disulfide cathode material based on two-dimensional nanosheets encapsulating a three-dimensional cube includes the following steps:

[0071] 1) Preparation of Cu₂O: 3.992 g of Cu(CH₃COO)₂·H₂O was weighed and dissolved in 100 mL of deionized water. Then, 20 mL of 6 M sodium hydroxide solution was added dropwise. After stirring at 500 rpm for 5 minutes, 0.8 g of D(+)-glucose was added to the solution, and the mixture was stirred for 1 hour. The entire process was carried out in a 70 °C water bath. The resulting reddish-brown precipitate was washed five times with deionized water and ethanol, and then dried under vacuum at 60 °C. The SEM image of the obtained product is shown below. Figure 1 and Figure 2 As shown, Cu₂O exhibits a cubic structure with a size of approximately 3–4 μm. XRD patterns are as follows. Figure 7 As shown, its characteristic peaks perfectly correspond to the standard card number PDF#78-2046.

[0072] 2) Preparation of Cu2S@NiS2: 0.08 g Cu2O, 0.16 g Ni(NO3)2·6H2O, 0.2 g thioacetamide, and 3 g polyvinylpyrrolidone (PVP, average molecular weight 8000, K16-18) were dissolved in 40 mL ethylene glycol. The resulting solution was then placed in a 50 mL Teflon-lined autoclave and maintained at 200 °C for 18 h. The obtained Cu2S@NiS2 sample was washed with ethanol and dried under vacuum at 60 °C. The resulting SEM images are shown below. Figure 3 and Figure 4 As shown, a layer of nanosheets, approximately 4–5 μm in size, can be clearly seen encapsulating the sample structure. TEM images show... Figure 5 and Figure 6 As shown, its outer lamellar structure is also clearly visible. XRD patterns are as follows... Figure 8 As shown, its characteristic peaks perfectly correspond to Cu2S standard card number PDF#53-0522 and NiS2 standard card number PDF#88-1709.

[0073] The preparation method of the 0.4M APC-0.4M LiBF4 electrolyte in Example 1 includes the following steps:

[0074] 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 2M phenyl magnesium chloride solution (solvent: tetrahydrofuran) 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 0.1875 g of anhydrous lithium tetrafluoroborate (LiBF4, 99.9%, Aladdin) in the above Mg... 2+ / Li + The mixed electrolyte was stirred for 12 hours to obtain a 0.4M APC-0.4M LiBF4 electrolyte.

[0075] Example 2

[0076] A method for preparing a copper sulfide@nickel disulfide cathode material based on two-dimensional nanosheets encapsulating a three-dimensional cube includes the following steps: carried out exactly as described in Example 1.

[0077] The preparation method of the 0.4M APC-0.4M LiTFSI electrolyte in Example 2 includes the following steps:

[0078] 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 2M phenyl magnesium chloride solution (solvent: tetrahydrofuran) 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 0.57417 g of lithium bis(trifluoromethanesulfonate)imide (LiTFSI, 99.9%, Aladdin) in the above Mg... 2+ / Li + Stirring in the mixed electrolyte for 12 hours yields a 0.4M MAPC-0.4M LiTFSI electrolyte.

[0079] Example 3

[0080] A method for preparing a copper sulfide@nickel disulfide cathode material based on two-dimensional nanosheets encapsulating a three-dimensional cube includes the following steps: carried out exactly as described in Example 1.

[0081] The preparation method of the 0.4M APC-0.4M LiCl electrolyte in Example 3 includes the following steps:

[0082] 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 2M phenyl magnesium chloride solution (solvent: tetrahydrofuran) 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 0.08478 g of anhydrous lithium chloride (LiCl, 99.9%, Aladdin) in the above Mg... 2+ / Li + Stirring the mixed electrolyte for 12 hours yields a 0.4M APC-0.4M LiCl electrolyte.

[0083] Comparative Example 1

[0084] A method for preparing Cu2S@NiS2 cathode material based on cubic nanoparticles includes the following steps:

[0085] 1) Preparation of Cu₂O: Weigh 3.992 g of Cu(CH₃COO)₂·H₂O and dissolve it in 100 mL of deionized water, then add 20 mL of 6M sodium hydroxide solution. After stirring at 500 rpm for 5 minutes, add 0.8 g of D(+)-glucose to the solution and stir for 1 hour. The entire process is carried out in a 70°C water bath. The resulting reddish-brown precipitate is washed several times with deionized water and ethanol, and then dried under vacuum at 60°C to obtain Cu₂O cubes.

[0086] 2) Preparation of Cu2S@NiS2: 0.08g Cu2O, 0.16g Ni(NO3)2·6H2O, 0.7g thioacetamide 3 g of polyvinylpyrrolidone (PVP) was dissolved in 40 mL of ethylene glycol, and the resulting solution was then placed in a 50 mL Teflon-lined autoclave and kept at 200 °C for 18 h. The resulting Cu₂S@NiS₂ sample was washed with ethanol and dried under vacuum at 60 °C. The SEM image of the sample is shown below. Figure 9 As shown, it can be observed that due to excessive sulfur powder, NiS2 exists in a particulate form and is randomly arranged on the Cu2S surface.

[0087] Comparative Example 2

[0088] A method for preparing Cu2S@NiS2 / Cu cathode material includes the following steps:

[0089] 1) Preparation of Cu₂O: Weigh 3.992 g of Cu(CH₃COO)₂·H₂O and dissolve it in 100 mL of deionized water, then add 20 mL of 6M sodium hydroxide solution. After stirring at 500 rpm for 5 minutes, add 0.8 g of D(+)-glucose to the solution and stir for 1 hour. The entire process is carried out in a 70°C water bath. The resulting reddish-brown precipitate is washed several times with deionized water and ethanol, and then dried under vacuum at 60°C to obtain Cu₂O cubes.

[0090] 2) Preparation of Cu2S@NiS2 / Cu: 0.08g Cu2O, 0.16g Ni(NO3)2·6H2O, 0.1g thioacetamide 3 g of polyvinylpyrrolidone (PVP) was dissolved in 40 mL of ethylene glycol, and the resulting solution was then placed in a 50 mL Teflon-lined autoclave and kept at 200 °C for 18 h. The resulting Cu₂S@NiS₂ / Cu sample was washed with ethanol and dried under vacuum at 60 °C. The SEM image of the product is shown below. Figure 10 As shown, due to insufficient thioacetamide, the NiS2 nanosheets are not obvious, and the excess PVP reduces Cu2O to Cu. The XRD pattern is shown below. Figure 12 As shown.

[0091] Comparative Example 3

[0092] A method for preparing a cubic Cu2S@NiS2 cathode material includes the following steps:

[0093] 1) Preparation of Cu₂O: 3.992 g of Cu(CH₃COO)₂·H₂O was weighed and dissolved in 100 mL of deionized water. Then, 20 mL of 6M sodium hydroxide solution was added, and the mixture was stirred at 500 rpm for 5 minutes. Next, 0.8 g of D(+)-glucose was added to the solution, and the mixture was stirred for 1 hour. The entire process was carried out in a 70°C water bath. The resulting reddish-brown precipitate was washed several times with deionized water and ethanol, and then dried under vacuum at 60°C to obtain Cu₂O cubes.

[0094] 2) Preparation of Cu2S@NiS2: 0.08g Cu2O, 0.16g Ni(NO3)2·6H2O, 0.2g thioacetamide and 1g Poly Vinylpyrrolidone (PVP) The solution was dissolved in 40 mL of ethylene glycol, and then placed in a 50 mL Teflon-lined autoclave and maintained at 200 °C for 18 h. The resulting Cu₂S@NiS₂ sample was washed with ethanol and dried under vacuum at 60 °C. The SEM image of the product is shown below. Figure 11 As shown, due to insufficient PVP content, NiS2 nanosheets cannot be composited with Cu2S.

[0095] Comparative Example 4

[0096] A method for preparing a cubic Cu2S cathode material includes the following steps:

[0097] 1) Preparation of Cu₂O: Weigh 3.992 g of Cu(CH₃COO)₂·H₂O and dissolve it in 100 mL of deionized water, then add 20 mL of 6M sodium hydroxide solution. After stirring at 500 rpm for 5 minutes, add 0.8 g of D(+)-glucose to the solution and stir for 1 hour. The entire process is carried out in a 70°C water bath. The resulting reddish-brown precipitate is washed several times with deionized water and ethanol, and then dried under vacuum at 60°C to obtain Cu₂O cubes.

[0098] 2) Preparation of Cu₂S: 0.08 g Cu₂O, 0.3 g thioacetamide, and 1 g polyvinylpyrrolidone (PVP) were dissolved in 40 mL ethylene glycol. The resulting solution was then placed in a 50 mL Teflon-lined autoclave and maintained at 200 °C for 18 h. The resulting Cu₂S… Cu2S sample Washed with ethanol. Dryed under vacuum at 60°C. SEM image of the product is shown below. Figure 13 As shown, it largely retains its cubic shape, but the surface has some depressions.

[0099] Example 4

[0100] The application of Cu2S@NiS2 material, which uses two-dimensional nanosheets to encapsulate three-dimensional cubes, as the positive electrode active material for lithium-magnesium dual-ion batteries, and 0.4M APC-0.4M LiCl as a novel electrolyte for lithium-magnesium dual-ion batteries, is described in the following details:

[0101] The product obtained in Example 3, based on the Cu2S@NiS2 material of a three-dimensional cube wrapped in two-dimensional nanosheets and the Cu2S cathode material of the product of Comparative Example 4, were used as active materials. They were mixed with conductive carbon black and PVDF in a mass ratio of 8:1:1 and stirred magnetically for 8 hours to disperse the mixture evenly in PVDF. The prepared slurry was then coated onto copper foil using a coater and placed in a vacuum drying oven at 80°C for 12 hours. After drying, the foil was pressed into tablets using a tablet press and then cut into small circular electrode sheets using a cutting machine.

[0102] The prepared electrode sheets were assembled into button cells in a glove box filled with high-purity argon gas and with water and oxygen levels ≤0.01ppm. Magnesium foil with a purity of Mg≥99.99% and a thickness of 70μm was cut to the size of a spacer. Copper foil with a purity of Cu≥99.99% and a thickness of 0.5nm 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.

[0103] Specific testing process: After assembling the magnesium-lithium dual-ion half-cell, set the steps on the Xinwei tester, first discharge to 0.01V with constant current, then charge to 2V with constant current, and repeat this cycle a certain number of times.

[0104] In battery assembly, the electrolytes prepared in Examples 1-3 were used respectively.

[0105] The test results and data are as follows:

[0106] Figure 14 Mg||Mg symmetric cell tests were conducted using 0.4M APC-0.4M LiCl, 0.4M APC-0.4M LiBF4, and 0.4M APC-0.4M LiTFSI electrolytes. The results demonstrate that 0.4M APC-0.4M LiCl, as an electrolyte for lithium-magnesium dual-ion batteries, exhibits low overpotential and long-term cycling stability, indicating that uniform deposition and extraction of magnesium have minimal nucleation barriers.

[0107] Figure 15Electrolytes of 0.4 M APC-0.4 M LiBF4, 0.4 M APC-0.4 M LiTFSI, and 0.4 M APC-0.4 M LiCl were used as cathode materials for lithium-magnesium dual-ion batteries, employing two-dimensional nanosheets encapsulating three-dimensional cubic Cu2S@NiS2 materials prepared in Example 1 at a concentration of 0.3 Ag. -1 Cyclic stability test results at current density: After 100 cycles, the specific capacity of the battery using 0.4M APC-0.4M LiCl as the electrolyte remained at 317 mAh g⁻¹. -1 The specific capacities of batteries using 0.4M APC-0.4M LiBF4 and 0.4M APC-0.4M LiTFSI as electrolytes remained at 181 and 252 mAh g, respectively. -1 .

[0108] Figure 16 Electrolytes of 0.4M APC-0.4M LiBF4, 0.4M APC-0.4M LiTFSI, and 0.4M APC-0.4M LiCl were used as cathode materials for lithium-magnesium dual-ion batteries, employing two-dimensional nanosheets encapsulating three-dimensional cubic Cu2S@NiS2 materials prepared in Example 1 at a concentration of 0.5 Ag. -1 Cyclic stability test results at current density (first at 0.2Ag) -1 (Activation was performed by cycling 10 times). After 200 cycles, the specific capacity of the battery using 0.4M APC-0.4M LiCl as the electrolyte remained at 260 mAh g. -1 The specific capacities of batteries using 0.4MAPC-0.4M LiBF4 and 0.4MAPC-0.4M LiTFSI as electrolytes remained at 142 and 227 mAh g, respectively. -1 .

[0109] Figure 17 Electrolytes of 0.4 M APC-0.4 M LiBF4, 0.4 M APC-0.4 M LiTFSI, and 0.4 M APC-0.4 M LiCl were used as cathode materials for lithium-magnesium dual-ion batteries, consisting of two-dimensional nanosheets encapsulating three-dimensional cubic Cu2S@NiS2 prepared in Example 1. The electrolytes were first applied to a 0.2 Ag... -1 Activation was performed for 10 cycles at current densities of 0.5, 0.8, 1.0, and 1.5 Ag. -1 Rate performance test results at current density. At the second rate gradient, the specific capacity corresponding to the 0.4M APC-0.4M LiCl electrolyte is 343 mAh g⁻¹. -1 (0.5Ag -1 ), 311mAh g -1 (0.8Ag -1 ), 301mAhg-1 (1.0Ag -1 ), 249mAhg -1 (1.5Ag -1 All of them have higher specific capacities than 0.4M APC-0.4M LiBF4 and 0.4M APC-0.4M LiTFSI.

[0110] Figure 18 An electrolyte of 0.4 M APC-0.4 M LiCl was used in Comparative Example 4, where cubic Cu₂S material was used as the cathode material in a lithium-magnesium dual-ion battery at a concentration of 0.1 Ag. -1 Cyclic stability test results at this current density show that after 50 cycles, the specific capacity remains at 166 mAh g⁻¹. -1 .

[0111] Figure 19 An electrolyte of 0.4 M APC-0.4 M LiCl was used in Comparative Example 4, where cubic Cu₂S material was used as the cathode material in a lithium-magnesium dual-ion battery at a concentration of 0.3 Ag. -1 Cyclic stability test results at this current density: after 200 cycles, the specific capacity remained at 28 mAh g⁻¹. -1 .

[0112] Figure 20 The APC electrolyte, along with the electrolytes prepared in Examples 1, 2, and 3, was used as the cathode material for a lithium-magnesium dual-ion battery based on a Cu2S@NiS2 material prepared in Example 1, which is composed of two-dimensional nanosheets encapsulating a three-dimensional cube. The electrolyte content was 0.2 Ag. -1 Impedance test after 50 cycles at the current density. Figure 21 yes Figure 20 Enlarged view within the dashed box. After 50 cycles, the battery with APC-LiCl as the electrolyte has the lowest impedance of 91.3Ω, while the battery with APC-LiBF4 as the electrolyte has an impedance of 169.4Ω. The impedances of the other two electrolytes are greater than 10Ω. 4 Ω. The preparation method of the APC electrolyte is as follows: 0.2667 g of anhydrous aluminum chloride (AlCl3, 99%, Aladdin) is dissolved in 3 mL of tetrahydrofuran (THF, Aladdin) solvent, and stirred vigorously at 800 rpm for 12 h. Then, 2 mL of 2M phenyl magnesium chloride solution (solvent: tetrahydrofuran) is added dropwise to the solution, and then the mixture is stirred magnetically for 12 h to obtain the electrolyte, which is the APC electrolyte.

[0113] Figure 22 The N2 adsorption-desorption isotherm of Cu2S@NiS2 prepared in Example 1 is shown below. Figure 23 This represents the corresponding pore size distribution. The specific surface area of ​​Cu2S@NiS2 is 9.4 m².2 g -1 The average pore size is 8.56 nm, indicating that the large surface area and abundant porosity of the sample provide more active sites, which is beneficial to electron / ion transfer.

[0114] The data underlined above do not meet the requirements of this invention.

[0115] The material structure prepared in this invention combines two-dimensional nanosheets and three-dimensional cubes, possessing a large specific surface area and average porosity, providing more active sites and ensuring sufficient contact with the electrolyte, thereby significantly improving battery performance. Simultaneously, the 0.4 mol / L APC-0.4 mol / L LiCl electrolyte exhibits low overpotential and stable cycle performance. When applied to the cathode material of lithium-magnesium dual-ion batteries in combination with 0.4 mol / L APC-0.4 mol / L LiCl as the electrolyte, it demonstrates advantages such as good cycle performance and high energy density.

[0116] The items underlined above do not meet the requirements of this invention.

[0117] 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 cuprous sulfide@nickel disulfide cathode material based on two-dimensional nanosheets encapsulating a three-dimensional cube, comprising the following steps: 1) Preparation of Cu2O cubes; 2) Cu2O cubes, nickel source, sulfur source and surfactant are mixed in an organic solvent and subjected to solvothermal treatment to obtain Cu2S@NiS2; The prepared copper sulfide@nickel disulfide cathode material based on two-dimensional nanosheets encapsulating three-dimensional cubes has a size of 4~6 μm, with Cu2S as the core and NiS2 as the shell; the outer NiS2 nanosheets have a thickness of 70±5nm for each layer.

2. The preparation method according to claim 1, characterized in that, In step 1), the method for preparing Cu2O cubes is as follows: disperse the copper source in water, add an alkaline solution dropwise, stir, add a reducing agent, and heat to react, thus obtaining the product.

3. According to the preparation method of claim 1, in step 2), the mass ratio of the Cu2O cube to the nickel source is in the range of 2:1 to 1:

2.

4. In the preparation method according to claim 1 or 3, in step 2), the mass ratio of the nickel source, sulfur source and surfactant is 4:3-5:60-80.

5. In the preparation method according to claim 1, in step 2), the sulfur source is thioacetamide and the surfactant is polyvinylpyrrolidone.

6. In the preparation method according to claim 1, in step 2), the organic solvent is ethylene glycol.

7. According to the preparation method of claim 1, in step 2), the solvothermal reaction conditions are 160~200℃ for 18~24 h.

8. A copper sulfide@nickel disulfide cathode material based on two-dimensional nanosheets encapsulating a three-dimensional cube, prepared by the preparation method according to any one of claims 1-7, characterized in that, The copper sulfide@nickel disulfide cathode material based on two-dimensional nanosheets encapsulating a three-dimensional cube has a size of 4~6 μm, with Cu2S as the core and NiS2 as the shell; the outer NiS2 nanosheets have a thickness of 70±5nm for each layer.

9. A lithium-magnesium dual-ion battery, characterized in that, The copper sulfide@nickel disulfide cathode material based on two-dimensional nanosheets encapsulating a three-dimensional cube, as described in claim 8, is used as the electrode material.

10. The lithium-magnesium dual-ion battery according to claim 9, characterized in that, The lithium-magnesium dual-ion battery uses 0.4M APC-0.4M LiCl as the electrolyte.

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