Hollow three-dimensional spherical microflower composite energy storage materials, their preparation methods and applications, and magnesium / sodium hybrid ion batteries.

Abstract

This invention provides a hollow three-dimensional spherical microflower composite energy storage material, its preparation method, and its application in magnesium / sodium hybrid ion batteries. First, a three-dimensional microflower-structured CoNiCu- precursor is prepared, followed by one-step selenization to obtain a three-dimensional hollow CoSe / NiSe2 / CuSe2 spherical microflower composite material with stacked long spines. The uniform branched structure increases electron and ion transfer, the hollow structure reduces volume changes during long-term charge and discharge, and the robust micro / nano framework enhances structural stability. The product is used as the cathode material in magnesium / sodium hybrid ion batteries, employing [Mg2Cl2][AlCl4]2-NaTFSI / TGM electrolyte and polarized Se... 2‑ Ions reduce Mg 2+ Migration barriers, avoiding Mg 2+ The electrolyte is difficult to dissociate and diffuse, resulting in low polarization and fast reaction kinetics, which gives the battery good cycle performance and stable coulombic efficiency, while improving the battery's charge and discharge capacity.

Description

Technical Field

[0001] This invention belongs to the technical field of magnesium / sodium hybrid ion battery cathode materials, specifically involving hollow three-dimensional spherical microflower composite energy storage materials, their preparation methods and applications, magnesium / sodium hybrid ion batteries, and the products used as cathode materials for magnesium / sodium hybrid ion batteries. Background Technology

[0002] Rechargeable batteries, characterized by long cycle life, high capacity and energy density, and safety and reliability, have significantly impacted the development of portable electronic devices, electric vehicles, and grid-connected energy storage systems. Conventional lithium-ion batteries (LIBs) are widely used due to their large capacity and long lifespan. However, the lithium crust content is only 0.0065%, and the limited resources, expensive lithium metal, and high dendrite risk have spurred the development of multivalent ion batteries using Mg, Ca, Al, and Zn. Recently, magnesium-based rechargeable batteries have gained attention due to their abundant magnesium reserves (approximately 2.5%) and high capacity (3833 mAh cm⁻¹). -3 It has become one of the most promising candidate batteries.

[0003] Previous studies on traditional rechargeable magnesium batteries (RMBs) have found that due to divalent magnesium ions (Mg... 2+ The limited extraction / insertion rate of Mg results in a slow redox reaction, severely hindering its practical application. To overcome this limitation... 2+ The slow ion dynamics, taking full advantage of the dendrite-free and stable Mg anode, in addition to exploring the design of novel electrode materials, involve introducing rapidly migrating ions (such as Li) into the system. + Na + Sodium-based electrolytes (e.g., lithium-based electrolytes) are an important strategy for improving electrochemical performance. Considering the diversity and high solubility of sodium-based salts, converting lithium-based electrolytes and anodes to sodium-based alternatives is advisable.

[0004] The Mg / Na hybrid ion battery (MNHB) uses Mg as the negative electrode, and Mg can be inserted into it. 2+ / Na + The material is the positive electrode, using Mg 2+ / Na + Hybrid ionic electrolytes represent a high-performance energy storage system with significant potential. Na + The introduction of ions can accelerate the reversible insertion of mixed ions, but in mixed ion systems, different ionic radii and coordination differences of ions in the electrolyte weaken the energy storage performance.

[0005] Therefore, designing novel electrolytes with fast ion diffusion kinetics and low corrosion, as well as ideal cathode materials for high-performance Mg / Na hybrid ion batteries, is an important research direction. Currently, materials with reasonable structures and capable of storing Mg are being developed. 2+ / Na+ High-performance, high-energy-density engineered cathode materials remain a challenge. Summary of the Invention

[0006] The purpose of this invention is to provide a hollow three-dimensional spherical microflower composite energy storage material and its preparation method. First, a three-dimensional microflower-structured CoNiCu- precursor is synthesized using low-cost raw materials. Then, a simple hydrothermal one-step selenization treatment is used to obtain a three-dimensional hollow CoSe / NiSe2 / CuSe2 spherical microflower composite material with stacked long spines. The prepared product has a hard structure, is not easily oxidized, and is easy to store. Furthermore, the preparation method is simple and efficient, the raw materials are readily available, and the cost is low.

[0007] Another objective of this invention is to provide an application of a hollow three-dimensional spherical microflower composite energy storage material for preparing cathode materials for magnesium / sodium hybrid ion batteries. The uniform dendritic structure increases electron and ion transfer, the hollow structure reduces volume changes during long-term charge-discharge processes, and the robust micro / nano framework enhances structural stability. Its stable structure provides a large specific surface area and active sites; it improves the battery's long-cycle stability, provides high reversibility, and enhances coulombic efficiency and rate performance.

[0008] The final objective of this invention is to provide a magnesium / sodium hybrid ion battery, comprising the above-mentioned hollow three-dimensional spherical microflower composite energy storage material as the battery cathode material.

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

[0010] This invention provides a method for preparing a hollow three-dimensional spherical microflower composite energy storage material, comprising the following steps:

[0011] 1) Cobalt source, nickel source, copper source and urea are mixed in water and subjected to hydrothermal reaction to prepare a CoNiCu precursor with a three-dimensional microflower structure;

[0012] 2) The three-dimensional micro-flower structure CoNiCu- precursor was dispersed in a solvent to obtain solution A; selenium powder was mixed in hydrazine hydrate to obtain solution B; under ultrasonic conditions, solution B was added dropwise to solution A, ultrasonically dispersed, and then hydrothermally reacted to obtain hollow three-dimensional spherical CoSe / NiSe2 / CuSe2 micro-flower composite material.

[0013] In step 1), the molar ratio of the cobalt source to the nickel source is 2-4:1-2, preferably 2:1;

[0014] In step 1), the molar ratio of the cobalt source to the copper source is 4-12:2-4, preferably 8:3;

[0015] In step 1), the molar ratio of the cobalt source to urea is 10-14:6-8, preferably 12:7.

[0016] In step 1), the ratio of cobalt source to water is 0.003 to 0.005 g / mL, preferably 0.004 g / mL;

[0017] In step 1), the cobalt source is selected from cobalt salts, specifically nitrates, sulfates, chlorides, and their hydrates;

[0018] The nickel source is selected from nickel salts, specifically nitrates, sulfates, chlorides, and their hydrates.

[0019] The copper source is selected from copper salts; it is one of nitrates, sulfates, chlorides, and their hydrates.

[0020] In step 1), preferably, the cobalt source is selected from cobalt nitrate hexahydrate, the nickel source is selected from nickel nitrate hexahydrate, and the copper source is selected from copper nitrate trihydrate;

[0021] In step 1), after the cobalt source, nickel source, copper source and urea are mixed in water, they are magnetically stirred and dispersed evenly for 30-45 minutes.

[0022] In step 1), the water is preferably deionized water; the main function of the urea is to utilize its reducing properties in hydrothermal reactions, and it is also a surfactant that can promote the surface reaction of metal salts and facilitate the reaction.

[0023] In step 1), the hydrothermal reaction refers to the reaction in a reactor at 100-140°C for 8-12 hours, preferably at 120°C for 10 hours;

[0024] In step 1), after the reaction is complete, the product is washed and dried. The washing process involves washing with deionized water and ethanol alternately 6-8 times, and the drying conditions are drying at 60℃ for 12-24 hours.

[0025] In step 2), the solvent is a mixture of water and alcohol, and the volume ratio of water to alcohol is 1-3:1-2, preferably 1:1; the water is deionized water and the alcohol is ethanol; the present invention uses a water and alcohol solution to better disperse the three-dimensional microflower structure; and the mixing of water and ethanol solutions will change the surface tension of the solution, thereby increasing the surface tension and promoting the reaction.

[0026] In step 2), the ratio of the CoNiCu-precursor of the three-dimensional microflower structure to the solvent is 0.0015 to 0.003 g / mL, preferably 0.0025 g / mL;

[0027] In step 2), the CoNiCu precursor with a three-dimensional microflower structure is dispersed in a solvent and ultrasonically dispersed for 10-25 min.

[0028] In step 2), the selenium powder is mixed in hydrazine hydrate at a water bath stirring temperature of 70-90°C, preferably 80°C; the stirring conditions refer to magnetic stirring, a stirring speed of 200-300 rpm, and a stirring time of 15-20 min.

[0029] In step 2), the hydrazine hydrate acts as a reducing agent and an antioxidant; the mass percentage concentration of the hydrazine hydrate solution is 40-80 wt%, preferably 50 wt%.

[0030] In step 2), the ratio of selenium powder to hydrazine hydrate is 0.02–0.04 g / mL, preferably 0.03 g / mL;

[0031] In step 2), the mass ratio of the selenium powder to the CoNiCu-precursor with the three-dimensional microflower structure is 1-3:1-2, preferably 2:1;

[0032] In step 2), solution B is added dropwise to solution A at a rate of 1-2 drops / second;

[0033] In step 2), the ultrasonic dispersion takes 10-15 minutes and has an ultrasonic frequency of 20-80 kHz.

[0034] In step 2), the hydrothermal reaction temperature is 160-200℃, preferably 180℃, and the reaction time is 10-14h, preferably 12h.

[0035] In step 2), after the reaction is complete, the product is washed and then dried. The washing is done by washing with water 6 to 8 times; the drying is done at 60 to 80°C in the air, preferably at 60°C, for 6 to 12 hours.

[0036] The preparation principle of this invention is as follows: First, a three-dimensional micro-flower CoNiCu precursor is formed under simple hydrothermal reaction conditions. Then, through selenization treatment: selenium powder acts as an oxidant. At high temperatures, the expanded thorn-like structure is caused by thermal expansion under strong selenium oxidant conditions. Furthermore, the selenium powder penetrates the precursor through solution, etching the center of the three-dimensional micro-flower structure, making it a hollow structure. The larger-volume thorn-like structure obtained by this invention has a larger specific surface area, increasing the number of active sites. The hollow structure also effectively mitigates the changes caused by volume expansion during cycling, promoting long-cycle performance. Moreover, this invention uses three active metal cations, which can greatly increase the number of redox states in the reaction system, generating more electrochemical active sites. At 120℃, nitrate and hydroxide ions synergistically interact with the three active metal cations to form a nanorod array, which then aggregates to form a three-dimensional micro-flower structure, i.e., a sea urchin structure. Selenium powder is reduced to Se in hydrazine hydrate solution. 2- Ions, ternary precursors and Se at high temperatures 2-Ions combine and react to form ternary selenides.

[0037] This invention provides a hollow three-dimensional spherical microflora composite energy storage material, prepared using the method described above. The hollow three-dimensional spherical microflora composite energy storage material is a hollow three-dimensional CoSe / NiSe2 / CuSe2 microflora nanomaterial, consisting of a hollow three-dimensional spherical microflora structure with a diameter of 5-6 μm and a long spike length of 50±10 nm, formed by stacked long spikes. 2+ / Na + The volume change caused by extraction reduces the pathways for electron and ion transport. Simultaneously, it increases the number of active sites for ions and electrons during charge and discharge, accelerating the redox reaction process and resulting in stable cycle performance and excellent rate performance.

[0038] This invention provides an application of a hollow three-dimensional spherical microflower composite energy storage material for preparing magnesium / sodium hybrid ion battery cathode material, thereby obtaining a magnesium / sodium hybrid ion battery cathode.

[0039] The present invention provides a magnesium / sodium hybrid ion battery, comprising a magnesium / sodium hybrid ion battery cathode prepared by using the above-mentioned hollow three-dimensional spherical microflower composite energy storage material as the cathode material, and also comprising an electrolyte.

[0040] The electrolyte is a highly soluble boron-free sodium bis(trifluoroethylsulfonyl)imide (TFSI) salt. The electrolyte is prepared by dispersing MgCl2 and AlCl3 in triethylene glycol dimethyl ether (TGM) and adding NaTFSI to prepare a 0.2M [Mg2Cl2][AlCl4]2-0.4M NaTFSI / TGM dual-salt ion electrolyte with a [Mg2Cl2] to [AlCl4]2 molar ratio of 2:1. By controlling the ion ratio of the additives, a wide voltage window, low overvoltage, and reversible magnesium plating / stripping [Mg2Cl2][AlCl4]2(MACC) / triethylene glycol dimethyl ether (TGM)-NaTFSI electrolyte is prepared. Magnesium / sodium hybrid ion batteries using CoSe / NiSe2 / CuSe2 as the positive electrode, operating with the modified electrolyte, exhibit high energy density, high stability, and large reversible capacity. It accelerates the reaction kinetics of magnesium and sodium ions, improves the safety and long cycle life of hybrid ion batteries, and lays a solid foundation for the practical application of magnesium / sodium hybrid ion batteries.

[0041] In this invention, the wide intergranular spacing and strong chemical bonds of transition metal selenides are beneficial to Mg. 2+ and Na + The reversible intersecting phases accelerate ion reaction kinetics. Simultaneously, the prepared hollow three-dimensional spherical CoSe / NiSe2 / CuSe2 microflower structure, combined with a highly soluble electrolyte, utilizes Se...2- The intercalated cathode for soft anions can break Mg 2+ The migration barrier is reduced, improving the overall structural stability. The hollow and three-dimensional structure mitigates the migration barrier of Mg. 2+ / Na + The volume change caused by extraction reduces the pathways for electron and ion transfer. By screening suitable ether-based solvents and controlling the ion ratio of additives, an electrolyte with a wide voltage window, low overvoltage, and reversible Mg plating / stripping was prepared.

[0042] The method for preparing a magnesium / sodium hybrid ion battery provided by the present invention includes the following steps:

[0043] S1. The prepared hollow three-dimensional spherical CoSe / NiSe2 / CuSe2 microflower composite material is used as the active material. It is mixed with conductive carbon black and polyvinylidene fluoride (PVDF) in a mass ratio of 8:1:1 and then dispersed in N-methylpyrrolidone (NMP). After magnetic stirring for 8 to 10 hours, the uniformly mixed slurry is coated onto copper foil using a coater. It is then placed in a vacuum drying oven at 60 to 80°C and dried for 24 to 36 hours. After drying, it is pressed into tablets using a tablet press and then cut into small circular electrode sheets with a diameter of 12 mm using a cutting machine.

[0044] S2. Assemble the electrode sheets prepared in step S1 into a button cell in a glove box filled with high-purity argon (Super 1220 / 750 / 900, water and oxygen values ​​≤0.01ppm). Use a magnesium / sodium mixed ion battery electrolyte: disperse MgCl2 and AlCl3 in triethylene glycol dimethyl ether (TGM) and add NaTFSI to prepare a 0.2M [Mg2Cl2][AlCl4]2-0.4M NaTFSI / TGM dual-salt ion electrolyte; the magnesium foil has a purity of Mg ≥99.99%, a thickness of 60μm, and is cut into a circular piece with a diameter of 16mm as the counter electrode magnesium sheet with an area of ​​2.0cm². 2 The copper sheet has a purity of Cu ≥ 99.99% and serves as a current collector. It is 0.5 mm thick and cut to the size of the electrode sheet. The loading mass of the active material is 1.2 mg / cm³. -2 Glass fiber membrane (GF / F) is used as the separator; the magnesium-based electrolyte content of each coin cell is approximately 100 μL.

[0045] S3. The specific method for assembling the battery is as follows: After adding one drop of electrolyte to the positive electrode shell, place the electrode plate, then add two drops of electrolyte and place the glass fiber. After adding two or three drops of electrolyte to the glass fiber, place the magnesium sheet as the counter electrode. Then place the gasket and spring sheet, cover the negative electrode shell, and use a hydraulic press to press and seal the battery. After 6 to 10 hours, the battery assembly is complete.

[0046] This invention employs a multi-level three-dimensional CoSe / NiSe2 / CuSe2 composite cathode and modification

[0047] This invention relates to a high-performance magnesium / sodium (Mg / Na) hybrid ion battery using a [Mg2Cl2][AlCl4]2-NaTFSI / TGM electrolyte. Currently, three main electrolytes are used: [Mg2Cl2][AlCl4]2+NaAlCl4 in dimethoxymethane, Mg(BH4)2 / Mg(TFSI)2+NaBH4 in DGM, and Mg(HMD)2 / AlCl3+NaTFSI in DGM. This invention modifies these electrolytes, improving the concentrations of MgCl2 and AlCl3 in TGM and investigating the solubility of sodium NaTFSI in TGM, thereby enhancing the battery's electrochemical performance. (Control n) [Mg2Cl2] 2+ :n [AlCl4] - = 1:2; [Mg2Cl2][AlCl4]2 was synthesized in TGM solvent, which can not only increase the solubility of the solution, but also provide Mg 2+ Highly soluble sodium TFSI salt was added, along with Na... + This electrolyte accelerates the electron movement rate, resulting in lower overpotential in magnesium / sodium hybrid ion batteries. The three-dimensional CoSe / NiSe2 / CuSe2 composite cathode utilizes this electrolyte to promote rapid ion and electron movement; the three-dimensional structure extends the transport distance, enhancing rate performance. Furthermore, the hollow structure also accelerates the shuttle movement of bimetallic ions within the electrolyte.

[0048] Compared with existing technologies, the hollow three-dimensional spherical CoSe / NiSe2 / CuSe2 microflower composite material prepared in this invention can well maintain the three-dimensional microflower structure and hollow structure, with a stable structure, providing a large specific surface area and active sites. The prepared CoSe / NiSe2 / CuSe2 composite material has stable electrochemical performance. When used with [Mg2Cl2][AlCl4]2-NaTFSI / TGM electrolyte, its high solubility and compatibility enable the battery to have good cycle performance and stable coulombic efficiency, while improving the charge and discharge capacity of the battery and enhancing the charge and discharge efficiency of the battery in terms of electrode process kinetics. The raw materials are inexpensive and the synthesis method is batch controllable. Attached Figure Description

[0049] Figure 1 SEM image of the CoNiCu-precursor prepared in Example 1;

[0050] Figure 2 SEM image of the three-dimensional spherical CoSe / NiSe2 / CuSe2 microflower composite material prepared in Example 1;

[0051] Figure 3 The XRD pattern of the CoSe / NiSe2 / CuSe2 microflower composite material prepared in Example 1;

[0052] Figure 4 SEM image of the CoNiCu-precursor prepared in Example 2;

[0053] Figure 5 SEM image of the three-dimensional spherical CoSe / NiSe2 / CuSe2 microflower composite material prepared in Example 2;

[0054] Figure 6 SEM image of the CoNiCu-precursor prepared in Example 3;

[0055] Figure 7 TEM image of the CoNiCu-precursor prepared in Example 3;

[0056] Figure 8 SEM image of the three-dimensional spherical CoSe / NiSe2 / CuSe2 microflower composite material prepared in Example 3;

[0057] Figure 9 SEM image of the hollow three-dimensional spherical CoSe / NiSe2 / CuSe2 microflower composite material prepared in Example 3;

[0058] Figure 10 TEM image of the hollow three-dimensional spherical CoSe / NiSe2 / CuSe2 microflower composite material prepared in Example 3;

[0059] Figure 11 The XRD pattern of the CoSe / NiSe2 / CuSe2 composite material prepared in Example 3;

[0060] Figure 12 SEM image of the three-dimensional spherical CoSe / NiSe2 / CuSe2 microflower composite material prepared in Comparative Example 1;

[0061] Figure 13 The CoSe / NiSe2 / CuSe2 composite material prepared in Example 3 was used as the cathode material for a magnesium / sodium hybrid ion battery at 0.4 mA cm⁻¹. -2 The deposition / dissolution cycle performance of symmetrical cells under different electrolytes was tested at different current densities.

[0062] Figure 14 The CoSe / NiSe2 / CuSe2 composite material prepared in Example 3 was used as the cathode material for a magnesium / sodium hybrid ion battery at a concentration of 0.2 A g. -1 Cyclic performance diagrams in different electrolytes at different current densities;

[0063] Figure 15 The CoSe / NiSe2 / CuSe2 composite material prepared in Example 3 was used as the cathode material for a magnesium / sodium hybrid ion battery in [Mg2Cl2][AlCl4]2 / TGM-NaTFSI electrolyte (MACC / TGM-NaTFSI) at 0.5 A g. -1 Cyclic performance at current density;

[0064] Figure 16 The CoSe / NiSe2 / CuSe2 composite material prepared in Example 3 was used as the cathode material for a magnesium / sodium hybrid ion battery in [Mg2Cl2][AlCl4]2 / TGM-NaTFSI electrolyte (MACC / TGM-NaTFSI) at 0.5 A g. -1 Charge-discharge curves under current density;

[0065] Figure 17 The CoSe / NiSe2 / CuSe2 composite material prepared in Example 3 was used as the cathode material for a magnesium / sodium hybrid ion battery in [Mg2Cl2][AlCl4]2 / TGM-NaTFSI electrolyte (MACC / TGM-NaTFSI) at a concentration of 0.2–1.0 A g. -1 Rate performance test results under current density;

[0066] Figure 18 The CoSe / NiSe2 / CuSe2 composite material prepared in Example 3 was used as the cathode material for a magnesium / sodium hybrid ion battery in [Mg2Cl2][AlCl4]2 / TGM-NaTFSI electrolyte (MACC / TGM-NaTFSI) at 2.0 A g. -1 Graphs showing long-cycle performance under current density;

[0067] Figure 19 The CoSe / NiSe2 / CuSe2 composite material prepared in Example 3 was used as the cathode material for a magnesium / sodium hybrid ion battery in [Mg2Cl2][AlCl4]2 / TGM-NaTFSI electrolyte (MACC / TGM-NaTFSI) at 0.1 A g. -1 Cyclic performance test graph under extreme conditions of 50℃ at current density;

[0068] Figure 20 The CoSe / NiSe2 / CuSe2 composite material prepared in Example 3 was used as the cathode material for a magnesium / sodium hybrid ion battery in [Mg2Cl2][AlCl4]2 / TGM-NaTFSI electrolyte (MACC / TGM-NaTFSI) at 0.1 A g. -1Cyclic performance test graph under extreme conditions of -10℃ at current density.

[0069] Figure 21 The CoSe / NiSe2 / CuSe2 composite material prepared for Comparative Example 1 was used as the cathode material for a magnesium / sodium hybrid ion battery in [Mg2Cl2][AlCl4]2 / TGM-NaTFSI electrolyte (MACC / TGM-NaTFSI) at 1.0 A g. -1 Cyclic performance test graph at current density. Detailed Implementation

[0070] 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.

[0071] Unless otherwise specified, all test materials and reagents used in the following examples are commercially available.

[0072] 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.

[0073] Example 1

[0074] A method for preparing a hollow three-dimensional spherical microflower composite energy storage material includes the following steps:

[0075] 1) Preparation of CoNiCu precursor:

[0076] At room temperature, 0.155 g Co(NO3)2·6H2O, 0.0776 g Ni(NO3)2·6H2O, 0.0483 g Cu(NO3)2·3H2O, and 0.018 g urea were weighed and dissolved in 40 mL of deionized water. The solution was magnetically stirred at 600 rpm for 30 min and then placed in a 50 mL polytetrafluoroethylene (PTFE) reactor. The reaction was carried out at 100 °C for 12 hours. After the reaction, the solution was cooled, centrifuged at 8000 rpm, washed four times with deionized water and twice with ethanol, and dried in a 60 °C oven for 12 h to obtain the CoNiCu precursor. Its SEM image is shown below. Figure 1 As shown in the figure, the shape is a relatively uneven three-dimensional micro-flower structure, and there are CoNiCu-precursor impurities with different morphologies; the reaction temperature and reaction time are not the optimal conditions described in this invention, so the product shape is not uniform.

[0077] 2) Preparation of CoSe / NiSe2 / CuSe2 composite materials:

[0078] 0.1 g of hollow three-dimensional spherical CoSe / NiSe2 / CuSe2 microflower composite material was ultrasonically dispersed for 10 min in a mixed solution of 20 mL water and 20 mL anhydrous ethanol to form solution A. 0.2 g of Se powder was weighed and added to 5 mL of hydrazine hydrate solution (50 wt%). The solution was stirred in an 80℃ water bath for 15 min at 300 rpm to obtain solution B. Solution B was then added drop by drop to solution A under ultrasonic conditions at a frequency of 60 kHz for 10 min. The mixture was then placed in a 50 mL Teflon-lined stainless steel autoclave and reacted at 160℃ for 12 h. After cooling, the mixture was washed six times alternately with deionized water and ethanol, and dried in a 60℃ oven for 12 h. The SEM image is shown below. Figure 2 As shown, a CoSe / NiSe2 / CuSe2 composite material was prepared, but its three-dimensional structure was not uniform; its XRD pattern is shown below. Figure 3 As shown, the selenization temperature is not the optimal temperature, and some of the excess selenium will remain, which can be seen in the XRD pattern as the diffraction peaks of the selenium.

[0079] Example 2

[0080] A method for preparing a hollow three-dimensional spherical microflower composite energy storage material includes the following steps:

[0081] 1) Preparation of CoNiCu precursor:

[0082] Weigh out 0.155 g Co(NO3)2·6H2O, 0.0776 g Ni(NO3)2·6H2O, 0.0483 g Cu(NO3)2·3H2O, and 0.018 g urea, dissolve them in 40 mL of deionized water, and stir magnetically at 600 rpm for 30 min. Then place the solution in a 50 mL polytetrafluoroethylene (PTFE) reactor liner and react at 140 °C for 8 hours. After the reaction, cool the solution, centrifuge at 8000 rpm, wash four times with deionized water and twice with ethanol, and dry in a 60 °C oven for 12 h to obtain the CoNiCu precursor. Its SEM image is shown below. Figure 4 As shown in the figure, its shape is a three-dimensional spherical-microflower structure. Because the reaction temperature is not the optimal temperature, the product shape has a small amount of inhomogeneity.

[0083] 2) Preparation of CoSe / NiSe2 / CuSe2 composite materials:

[0084] 0.1 g of hollow three-dimensional spherical CoSe / NiSe2 / CuSe2 microflower composite material was ultrasonically dispersed for 10 min in a mixed solution of 20 mL water and 20 mL anhydrous ethanol to form solution A. 0.2 g of Se powder was weighed and added to 5 mL of hydrazine hydrate solution (50 wt%). The solution was stirred in an 80℃ water bath for 15 min at 300 rpm to obtain solution B. Solution B was then added drop by drop to solution A under ultrasonic conditions at a frequency of 60 kHz for 10 min. The mixture was then placed in a 50 mL Teflon-lined stainless steel autoclave and reacted at 200℃ for 10 h. After cooling, the mixture was washed six times alternately with deionized water and ethanol, and dried in a 60℃ oven for 12 h to obtain the CoSe / NiSe2 / CuSe2 composite material. Its SEM image is shown below. Figure 5 As shown, however, due to its high reaction temperature, which is not the optimal temperature, the surface spiky structure melted, the three-dimensional structure became uneven, and agglomeration occurred.

[0085] Example 3 (Optimal Reaction Conditions)

[0086] A method for preparing a hollow three-dimensional spherical microflower composite energy storage material includes the following steps:

[0087] 1) Preparation of CoNiCu precursor:

[0088] Weigh out 0.155 g Co(NO3)2·6H2O, 0.0776 g Ni(NO3)2·6H2O, 0.0483 g Cu(NO3)2·3H2O, and 0.018 g urea, dissolve them in 40 mL of deionized water, and stir magnetically at 600 rpm for 30 min. Then place the solution in a 50 mL polytetrafluoroethylene (PTFE) reactor liner and react at 120 °C for 10 hours. After the reaction, cool the solution, centrifuge at 8000 rpm, wash four times with deionized water and twice with ethanol, and dry in a 60 °C oven for 12 h to obtain the CoNiCu precursor. Its SEM image is shown below. Figure 6 As shown, its TEM image is as follows Figure 7 As shown in the figure, it can be seen that it is composed of nanorods with a diameter of about 50 nm, and its shape is a three-dimensional spherical-microflower structure because the reaction temperature and reaction time are optimal; the product has a uniform morphology.

[0089] 2) Preparation of CoSe / NiSe2 / CuSe2 composite materials:

[0090] 0.1 g of hollow three-dimensional spherical CoSe / NiSe2 / CuSe2 microflower composite material was ultrasonically dispersed for 10 min in a mixed solution of 20 mL water and 20 mL anhydrous ethanol to form solution A. 0.2 g of Se powder was weighed and added to 5 mL of hydrazine hydrate solution (50 wt%). The solution was stirred in an 80℃ water bath for 15 min at 300 rpm to obtain solution B. Solution B was then added drop by drop to solution A under ultrasonic conditions at a frequency of 60 kHz for 10 min. The mixture was then placed in a 50 mL Teflon-lined stainless steel autoclave and reacted at 180℃ for 12 h. After cooling, the mixture was washed six times alternately with deionized water and ethanol, and dried in a 60℃ oven for 12 h to obtain the CoSe / NiSe2 / CuSe2 composite material. Its SEM image is shown below. Figure 8 and Figure 9 As shown, its TEM image is as follows Figure 10 As shown in the figure, its three-dimensional micro-flower structure is well-formed, and it can be seen that its structure is hollow; its XRD pattern is as follows. Figure 11 As shown, they are consistent with JCPDS Joint Committee on Diffraction Standards Nos. 88-1711 (NiSe2), 82-0446 (CuSe2), and 89-2004 (CoSe), respectively.

[0091] Comparative Example 1

[0092] A method for preparing a hollow three-dimensional spherical microflower composite energy storage material includes the following steps:

[0093] 1) Preparation of CoNiCu precursor: Follow step 1) in Example 3;

[0094] 2) Preparation of CoSe / NiSe2 / CuSe2 composite materials:

[0095] 0.1 g of hollow three-dimensional spherical CoSe / NiSe2 / CuSe2 microflower composite material was ultrasonically dispersed in a mixture of 20 mL water and 20 mL anhydrous ethanol to form solution A. 0.2 g of Se powder was weighed and added to 5 mL of hydrazine hydrate solution (50 wt%). The solution was stirred in an 80°C water bath for 15 min at 300 rpm to obtain solution B. Under ultrasonic conditions, solution B was added drop by drop to solution A, and the mixture was ultrasonically sonicated for 10 min. The mixture was then placed in a 50 mL Teflon-lined stainless steel autoclave. The reaction was carried out at 140℃ for 12 hours. After cooling, the mixture was washed six times alternately with deionized water and ethanol, and then dried in an oven at 60°C for 12 hours to obtain the CoSe / NiSe2 / CuSe2 composite material. Its SEM image is shown below. Figure 12As shown in the figure, the reaction temperature is too low, below the range of the present invention, so the elemental selenium cannot undergo redox reaction. The selenization reaction will not occur completely, and the three-dimensional structure and hollow structure will not change. Its structure is not changed from the structure of the precursor. The size of its spiky structure does not increase, and the hollow structure is not formed. Therefore, it cannot play a key role in the subsequent electrochemical reaction.

[0096] Example 4 (Comparative Example of Electrolyte)

[0097] An application of hollow three-dimensional spherical microflower composite energy storage material CoSe / NiSe2 / CuSe2 in batteries is described, specifically as an active material in the preparation of a magnesium / sodium hybrid ion battery cathode, thereby preparing a magnesium / sodium hybrid ion battery.

[0098] Specifically:

[0099] S1. The hollow three-dimensional spherical CoSe / NiSe2 / CuSe2 microflower composite material prepared in Example 3 was used as the active material. It was mixed with conductive carbon black and PVDF in a mass ratio of 8:1:1 and then dispersed in NMP. After magnetic stirring for 8 hours, the uniformly mixed slurry was coated onto copper foil using a coater. It was placed in a vacuum drying oven at 80°C and dried for 24 hours. After drying, it was pressed into tablets using a tablet press and then cut into small circular electrode sheets using a cutting machine.

[0100] S2. Assemble the prepared electrode sheets into button batteries in a glove box filled with high-purity argon gas (Super 1220 / 750 / 900, water and oxygen values ​​≤0.01ppm). Magnesium / sodium mixed-ion battery electrolyte: Disperse 0.152g anhydrous MgCl2 and 0.215g AlCl3 in 4mL triethylene glycol dimethyl ether (TGM) and stir magnetically for 12h to prepare 0.2M [Mg2Cl2][AlCl4]2 (MACC) / TGM Electrochemical performance of single-salt electrolyte compared to that of dual-salt electrolyte.

[0101] Example 5 (Comparative Example of Electrolyte)

[0102] An application of hollow three-dimensional spherical microflower composite energy storage material CoSe / NiSe2 / CuSe2 in batteries is described, specifically as an active material in the preparation of a magnesium / sodium hybrid ion battery cathode, thereby preparing a magnesium / sodium hybrid ion battery.

[0103] Specifically, it is carried out according to Example 4, except that the magnesium / sodium mixed-ion battery electrolyte is: MgCl2 and AlCl3 are stirred and dispersed in... Diethylene glycol dimethyl ether (DGM)Sodium NaTFSI was added to prepare a 0.2M [Mg2Cl2][AlCl4]2 / DGM-0.4M NaTFSI dual-salt electrolyte (MACC / DGM-NaTFSI).

[0104] Example 6 (Comparative Example of Electrolyte)

[0105] An application of hollow three-dimensional spherical microflower composite energy storage material CoSe / NiSe2 / CuSe2 in batteries is described, specifically as an active material in the preparation of a magnesium / sodium hybrid ion battery cathode, thereby preparing a magnesium / sodium hybrid ion battery.

[0106] Specifically, it is carried out according to Example 4, except that the magnesium / sodium mixed-ion battery electrolyte is: MgCl2 and AlCl3 are stirred and dispersed in... Dimethyl ether (DME) In this process, sodium NaTFSI was added to prepare a 0.2M [Mg2Cl2][AlCl4]2 / DME-0.4M NaTFSI dual-salt electrolyte (MACC / DME-NaTFSI).

[0107] Example 7 (Optimal Electrolyte)

[0108] An application of hollow three-dimensional spherical CoSe / NiSe2 / CuSe2 microflower composite material in batteries, specifically as an active material to prepare the positive electrode of magnesium / sodium hybrid ion battery, and then to prepare magnesium / sodium hybrid ion battery.

[0109] Specifically, the process was carried out according to Example 4, except that the magnesium / sodium mixed-ion battery electrolyte was prepared by dispersing MgCl2 and AlCl3 in triethylene glycol dimethyl ether (TGM) and adding sodium NaTFSI to prepare a 0.2M [Mg2Cl2][AlCl4]2 / TGM-0.4M NaTFSI dual-salt electrolyte (MACC / TGM-NaTFSI).

[0110] The magnesium foil used in battery assembly has a purity of Mg ≥ 99.99% and a thickness of 60 μm, and is cut to the size of a spacer. The copper sheet has a purity of Cu ≥ 99.99% and a thickness of 0.5 mm, and is cut to the size of an electrode sheet.

[0111] The specific method for assembling the battery is as follows: After adding one drop of electrolyte to the positive electrode shell, place the electrode plate, then add two drops of electrolyte and place the glass fiber, then add three drops of electrolyte to the glass fiber and place the magnesium sheet as the counter electrode, then place the gasket and spring, cover the negative electrode shell, press and seal the battery with a hydraulic press, and leave it for 10 hours to complete the battery assembly.

[0112] The deposition / dissolution cycle performance of the symmetric Mg anode in magnesium / sodium hybrid ion batteries using the MACC / TGM single-ion electrolyte prepared in Example 4, the MACC / DGM-NaTFSI prepared in Example 5, the MACC / DME-NaTFSI prepared in Example 6, and the MACC / TGM-NaTFSI dual-salt electrolyte prepared in Example 7 was tested. The results are as follows: Figure 13 As shown, a symmetric Mg|Mg cell using 0.2 M [Mg₂Cl₂][AlCl₄]₂ (MACC) exhibited a high overvoltage in a triethylene glycol dimethyl ether (MACC / TGM) electrolyte, indicating that metallic Mg cannot be completely electroplated / stripped in a sodium-free electrolyte; after the addition of NaTFSI salt and cycling stabilization, the overvoltage was maintained at 400 mV for 550 hours. The MACC / TGM-NaTFSI electrolyte exhibited a lower overvoltage and showed better Mg deposition / dissolution behavior than other ether solvents. And at a current density of 0.2 A g -2 Cyclic performance tests were conducted under different electrolytes, and the results are as follows: Figure 14 As shown, the battery using MACC / TGM-NaTFSI electrolyte still retains 391.2 mAh g after 120 cycles. -1 The high capacity and superior cycle performance of the MACC / DGM-NaTFSI electrolyte demonstrate that the magnesium / sodium hybrid ion battery exhibits better cycle stability with the MACC / DGM-NaTFSI electrolyte. The MACC / DGM-NaTFSI electrolyte has the second lowest overvoltage, while the MACC / DME-NaTFSI electrolyte has a higher overvoltage and poorer electrochemical performance.

[0113] Magnesium / sodium hybrid ion battery using MACC / TGM-NaTFSI mixed electrolyte at 0.5 A g -1 Cyclic performance and charge-discharge curve testing of button cells were conducted at a current density of 0.2 A g. -1 0.4Ag -1 0.6A g -1 0.8Ag -1 and 1.0A g -1 Rate performance was tested under varying current and at 2.0Ag. -1 Long-cycle performance at high current density, as shown in the results Figure 15 , Figure 16 , Figure 17 , Figure 18 As shown, the magnesium / sodium hybrid ion battery at 0.5 A g -1 After 500 cycles, it has a capacity of 230.1 mAh g. -1 High capacity ( Figure 15 The coulombic efficiency (CE) exceeds 99.4%. Constant current charge-discharge curves ( Figure 16 It exhibited a smooth discharge plateau and high cycling stability in the range of 0.2–1.0 A g. -1 At the specified current densities, the specific capacities after 10 cycles were 436.6.3, 420.1, 388.0, 355.6, and 327.7 mAh g, respectively. -1 When the current density recovers to 0.2 A g after three rounds -1 At that time, the capacity recovered to 349.8mAh g. -1 This indicates highly reversible rate performance. Figure 17 ). In 2A g -1 After 2000 cycles, the capacity remained at 115.5 mAh g. -1 The coulomb efficiency remains at 99.8%, indicating significant application potential. Figure 18 Using [Mg2Cl2][AlCl4]2-NaTFSI modified in highly soluble TGM as the electrolyte and hollow CoSe / NiSe2 / CuSe2 composite material as the positive electrode material, the NaTFSI additive improved the reaction kinetics at the electrode-electrolyte interface and enhanced the Mg2Cl2-NaTFSI-modified electrolyte. 2+ / Na + The rapid transport of ions extends the cycle life of magnesium / sodium hybrid ion batteries.

[0114] Magnesium / sodium hybrid ion batteries, composed of a CoSe / NiSe2 / CuSe2 composite material as the cathode and MACC / TGM-NaTFSI electrolyte, also exhibit excellent electrochemical performance at different temperatures. The results are as follows... Figure 19 , Figure 20 As shown, after 150 cycles at 50°C, the capacity is 194.8 mAh g. -1 The coulomb efficiency is 99.8%. Figure 19 After 200 cycles at -10℃, the capacity is 228.1 mAh g. -1 The coulomb efficiency is 98.8%. Figure 20 It exhibits excellent temperature resistance under some extreme conditions. Furthermore, the cycling performance under different selenization conditions was compared (Example 3 and Comparative Example 1), such as... Figure 21 As shown in the figure, the cathode material treated with selenization at 180℃ exhibits better long-cycle performance when applied to magnesium / sodium hybrid ion batteries. Its advantages are attributed to its larger specific surface area and hollow structure.

[0115] The hollow three-dimensional spherical CoSe / NiSe2 / CuSe2 microflower nanomaterials prepared in this invention can well maintain the three-dimensional structure and microflower-hollow structure. The uniform dendritic structure increases the transfer of electrons and ions, the hollow structure reduces the volume change during long-term charge and discharge, and the robust micro-nano framework enhances the structural stability. Its stable structure provides a large specific surface area and active sites. The prepared CoSe / NiSe2 / CuSe2 composite nanomaterials are stable, do not easily degrade in air, and are easy to store. The prepared CoSe / NiSe2 / CuSe2 composite nanomaterials can be used as positive electrode materials for magnesium / sodium hybrid ion batteries, with [Mg2Cl2][AlCl4]2 and bis(trifluorovinylsulfonyl)imide (TFSI) anionic sodium salt as the mixed ionic electrolyte in triethylene glycol dimethyl ether (TGM). Polarized Se 2- Ions reduce Mg 2+ Migration barriers, avoiding Mg 2+ It is difficult to dissociate and diffuse in the electrolyte, achieving low polarization and fast reaction kinetics, which gives the battery good cycle performance and stable coulombic efficiency, while improving the battery's charge and discharge capacity; the raw materials are inexpensive to prepare and the synthesis method is batch controllable.

[0116] The data 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 hollow three-dimensional spherical microflower composite energy storage material, characterized in that, The preparation method comprises the following steps: 1) mixing a cobalt source, a nickel source, a copper source and urea in water to perform a hydrothermal reaction to prepare a three-dimensional micro-flower structure CoNiCu-precursor; 2) dispersing the three-dimensional micro-flower structure CoNiCu-precursor in a solvent to obtain solution A; mixing selenium powder in hydrazine hydrate to obtain solution B; under ultrasonic condition, dropping solution B into solution A, ultrasonic dispersion, and then performing a hydrothermal reaction to obtain a hollow three-dimensional spherical CoSe / NiSe2 / CuSe2 micro-flower composite material; In step 1), the molar ratio of the cobalt source to the nickel source is 2-4:1-2, and the molar ratio of the cobalt source to the copper source is 4-12:2-4; in step 1), the molar ratio of the cobalt source to urea is 10-14:6-8; In step 1), the hydrothermal reaction refers to a reaction in a reaction kettle at 100-140℃ for 8-12 h; In step 2), the hydrothermal reaction temperature is 160-200℃, and the reaction time is 10-14 h.

2. The production method according to claim 1, characterized by, In step 2), the solvent is a mixed solvent of water and alcohol, and the volume ratio of water to alcohol is 1-3:1-2.

3. The preparation method according to claim 1, characterized in that, In step 2), the mass ratio of the selenium powder to the three-dimensional micro-flower structure CoNiCu-precursor is 1-3:1-2.

4. The hollow three-dimensional spherical microflower composite energy storage material prepared by the method of any one of claims 1-3, characterized in that, The hollow three-dimensional spherical micro-flower composite energy storage material is a hollow three-dimensional CoSe / NiSe2 / CuSe2 micro-flower nanomaterial, which is a hollow three-dimensional spherical micro-flower structure with a diameter of 5-6μm and a long spine length of 50±10 nm.

5. The use of the hollow three-dimensional spherical microflower composite energy storage material according to claim 4, characterized in that, The hollow three-dimensional spherical micro-flower composite energy storage material is used to prepare a magnesium / sodium hybrid ion battery positive electrode material to obtain a magnesium / sodium hybrid ion battery positive electrode.

6. A magnesium / sodium hybrid ionic battery, characterized in that, The magnesium / sodium hybrid ion battery positive electrode comprises the magnesium / sodium hybrid ion battery positive electrode of claim 5.

7. The magnesium / sodium hybrid ionic battery of claim 6, wherein, The magnesium / sodium hybrid ion battery positive electrode further comprises an electrolyte, and a preparation method of the electrolyte is as follows: dispersing MgCl2 and AlCl3 in triethylene glycol dimethyl ether (TGM) by stirring, and adding NaTFSI to configure 0.2 M [Mg2Cl2][AlCl4]2-0.4 M NaTFSI / TGM double salt ionic electrolyte.

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