Hollow zinc sulfide nanotubes for positive electrode of aqueous zinc-sulfur battery and preparation method thereof

Abstract

This invention discloses a hollow zinc sulfide nanotube for the cathode of an aqueous zinc-sulfur battery and its preparation method. The preparation method includes the following steps: S1, preparing a hollow zinc sulfide nanotube containing Zn... 2+ The metal salt is dissolved in an aqueous solution of alkali metal hydroxide, stirred evenly, and then a polyol organic solvent is added. The mixture is then placed in a reaction vessel for a hydrothermal reaction to obtain zinc oxide nanorods. S2: Zinc oxide nanorods and a sulfiding agent are dissolved in a mixed solution of ethanol and water, and stirred to carry out a sulfidation reaction, obtaining zinc sulfide-coated zinc oxide material. S3: The zinc sulfide-coated zinc oxide material is uniformly dispersed in an aqueous etchant solution, and stirred to carry out a chemical etching reaction, obtaining hollow zinc sulfide nanotube material. The hollow zinc sulfide nanotube cathode prepared by this invention not only has good conductivity, which can improve polarization and enhance charge-discharge performance, but also provides space for the volume change caused by sulfur during oxidation, thereby reducing structural damage to the electrode and improving cycle stability.

Description

Technical Field

[0001] This invention relates to the field of aqueous zinc-ion battery technology, specifically to a hollow zinc sulfide nanotube for the cathode of an aqueous zinc-sulfur battery and its preparation method. Background Technology

[0002] With the rapid development of society, economy, and technology, various electronic devices are upgrading towards higher efficiency and lighter, more portable designs, posing significant challenges to battery capacity and performance. Lithium-ion and sodium-ion batteries are the most widely used batteries; however, due to their disadvantages such as safety concerns, high cost, and poor rate performance, research focus is gradually shifting from lithium-ion and sodium-ion batteries to another emerging battery—aqueous zinc-sulfur batteries.

[0003] Aqueous zinc-sulfur batteries use sulfur as the positive electrode active material and zinc metal sheets as the negative electrode, completing the charging and discharging process through the oxidation-reduction process of the positive and negative electrode materials. Compared with other batteries, aqueous zinc-sulfur batteries have the following advantages: 1) Intrinsic safety: Aqueous electrolytes have low toxicity, low volatility, and are not easily flammable or explosive, improving battery safety. 2) Low cost and environmental friendliness: Firstly, aqueous electrolytes have certain cost advantages over organic electrolytes in terms of solvents and inorganic zinc salts. Secondly, zinc and sulfur are abundant in the Earth's crust. Furthermore, aqueous zinc-sulfur batteries have relatively small environmental impact during production and recycling, reducing production costs. 3) Good rate performance: The high ionic conductivity of aqueous electrolytes allows for rapid charging and discharging of the battery. 4) High specific capacity: Sulfur has a high theoretical specific capacity of 1675 mAh / g, and the zinc negative electrode also has a theoretical specific capacity as high as 820 mAh / g.

[0004] Zinc-sulfur batteries offer significant advantages, but they also face pressing issues, primarily concerning the cathode materials: 1) Volume expansion: During dynamic cycling, the sulfur cathode undergoes volume changes, leading to mechanical damage and potential electrode structure collapse. 2) Kinetic limitations: Both the reactant S8 and the discharge end product ZnS exhibit low electronic and ionic conductivity, resulting in rapid capacity decay, low coulombic efficiency, and short cycle life.

[0005] Therefore, the industry urgently needs a new technology for cathode materials used in aqueous zinc-sulfur batteries. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a hollow zinc sulfide nanotube for the cathode of an aqueous zinc-sulfur battery and its preparation method. This ingenious cathode design solves the pain points of cathode materials in aqueous zinc-sulfur batteries. The hollow zinc sulfide nanotube cathode not only exhibits good conductivity, improving polarization and enhancing charge-discharge performance, but also provides space for the volume changes caused by sulfur during oxidation, thereby reducing structural damage to the electrode and improving cycle stability.

[0007] The present invention adopts the following technical solution:

[0008] A method for preparing hollow zinc sulfide nanotubes for the cathode of an aqueous zinc-sulfur battery includes the following steps:

[0009] S1, Preparation of zinc oxide nanorods: Zn-containing nanorods... 2+ The metal salt is dissolved in an aqueous solution of alkali metal hydroxide, stirred evenly, and then polyol organic solvent is added in proportion. The mixture is placed in a reaction vessel for hydrothermal reaction to obtain zinc oxide nanorods.

[0010] S2, Surface sulfidation: Dissolve the zinc oxide nanorods and sulfiding agent from step S1 in a mixed solution of ethanol and water, and then stir at a certain temperature to carry out the sulfidation reaction to obtain zinc oxide material coated with zinc sulfide.

[0011] S3. Chemical etching: The zinc sulfide-coated zinc oxide material from step S2 is uniformly dispersed in an aqueous etching agent solution, and then stirred at a certain temperature to carry out a chemical etching reaction to obtain hollow zinc sulfide nanotube material.

[0012] The step S1 contains Zn. 2+ The metal salt is at least one selected from zinc acetate dihydrate, zinc nitrate hexahydrate, zinc chloride, zinc nitrate, and zinc sulfate; the Zn-containing... 2+ The molar concentration of the metal salt is 0.1–0.5 mol / L.

[0013] In step S1, the alkali metal hydroxide is at least one of lithium hydroxide, sodium hydroxide, and potassium hydroxide; the molar concentration of the alkali metal hydroxide is 6 to 10 mol / L.

[0014] In step S1, the polyol solvent is at least one of ethylene glycol, propylene glycol, and glycerol; the volume ratio between the polyol solvent and the aqueous solution is (2-5):1.

[0015] The hydrothermal reaction temperature in step S1 is 120–180°C, and the reaction time is 12–24 h.

[0016] In step S2, the sulfiding agent is at least one of thioacetamide, thiourea, and sodium sulfide; the molar ratio between the added zinc oxide nanorods and the sulfiding agent is (1-12):1.

[0017] In step S2, the volume ratio of the ethanol and water mixture is 1:(2-4).

[0018] In step S2, the temperature of the sulfidation reaction is 60–80°C, and the reaction time is 2–8 hours.

[0019] In step S3, the chemical etching agent is at least one of ammonia, ammonium chloride, sodium hydroxide, and potassium hydroxide; the molar concentration of the aqueous etching agent solution is 1–3 mol / L.

[0020] In step S3, the temperature of the chemical etching reaction is 60–80°C, and the reaction time is 6–12 h.

[0021] A hollow zinc sulfide nanotube for use as the cathode in an aqueous zinc-sulfur battery was prepared according to the above method.

[0022] An application of hollow zinc sulfide nanotubes prepared according to the above preparation method in an aqueous zinc-sulfur battery, wherein the aqueous zinc-sulfur battery is assembled from the hollow zinc sulfide nanotubes as the positive electrode, zinc metal sheets as the negative electrode, a separator, and an aqueous electrolyte.

[0023] The hollow zinc sulfide nanotubes are mixed with conductive carbon black and binder in a certain proportion to form a slurry, which is then coated on the surface of the current collector and dried to obtain the positive electrode sheet of the aqueous zinc-sulfur battery.

[0024] The mass ratio of the hollow zinc sulfide nanotubes to the conductive carbon black and binder is one of 9:0.5:0.5, 8:1:1, 7:2:1, and 6:3:1.

[0025] The conductive carbon black is at least one of Super P, acetylene black, and Ketjen black.

[0026] The binder is at least one of LA133, sodium alginate, PVDF, and PTFE.

[0027] The current collector is at least one of stainless steel foil, stainless steel mesh, titanium foil, titanium mesh, carbon fiber cloth, carbon paper, and graphite paper.

[0028] The diaphragm is at least one of glass fiber, non-woven fabric, and proton exchange membrane;

[0029] The aqueous electrolyte is prepared by dissolving zinc metal salt in a deionized aqueous solution, and its concentration is 1-10 mol / L.

[0030] The zinc metal salt is at least one of zinc sulfate, zinc chloride, zinc nitrate, zinc acetate, zinc perchlorate, zinc gluconate, zinc trifluoromethanesulfonate, and zinc bis(trifluoromethanesulfonyl)imide.

[0031] The technical solution of this invention has the following advantages:

[0032] A. This invention uses zinc oxide nanorods as templates. Zinc oxide is coated with zinc sulfide through surface sulfidation, and then unreacted zinc oxide is removed by chemical etching to obtain hollow zinc sulfide nanotubes. These hollow zinc sulfide nanotubes are then paired with a zinc metal anode as the positive electrode material and injected into an aqueous electrolyte to assemble an aqueous zinc-sulfur battery. The hollow zinc sulfide nanotube positive electrode material exhibits excellent conductivity, effectively improving battery polarization and significantly enhancing the charge-discharge performance of the aqueous zinc-sulfur battery. This material provides ample buffer space for the volume changes generated during sulfur oxidation, significantly reducing damage to the electrode structure and thus enhancing the battery's cycle stability.

[0033] B. This invention provides a variety of optional metal salts, alkali metal hydroxides, and polyol solvents during the preparation process, making the preparation process more flexible and controllable. The prepared hollow zinc sulfide nanotubes are not only suitable for aqueous zinc-sulfur battery cathodes, but their unique properties may also be extended to other related fields, showing broad application potential. Attached Figure Description

[0034] To more clearly illustrate the specific embodiments of the present invention, the accompanying drawings used in the specific embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0035] Figure 1 Images (a)-(d) are scanning electron microscope images of hollow zinc sulfide nanotubes prepared by zinc oxide nanorods and thioacetamide in Example 1 of the present invention at molar ratios of 1:1, 3:1, 6:1 and 12:1, respectively.

[0036] Figure 2 The graph shows the cycle performance test results of zinc-sulfur batteries assembled with hollow zinc sulfide as the positive electrode, which are prepared by zinc oxide nanorods and thioacetamide in molar ratios of 1:1, 3:1, 6:1 and 12:1, as involved in this invention.

[0037] Figure 3 The graph shows the rate performance test results of zinc-sulfur batteries assembled with hollow zinc sulfide as the positive electrode, which are prepared by using zinc oxide nanorods and thioacetamide in molar ratios of 1:1, 3:1, 6:1 and 12:1, as involved in this invention. Detailed Implementation

[0038] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0039] Example 1:

[0040] This embodiment provides a method for preparing hollow zinc sulfide nanotubes for the positive electrode of an aqueous zinc-sulfur battery. The zinc-sulfur battery is mainly assembled from hollow zinc sulfide nanotubes as the positive electrode, zinc metal sheets as the negative electrode, a separator, and an aqueous electrolyte.

[0041] The method for preparing the hollow zinc sulfide nanotubes includes the following steps:

[0042] S1. Preparation of zinc oxide nanorods: 0.015 mol zinc acetate dihydrate was dissolved in 45 ml of 0.3 mol sodium hydroxide aqueous solution. After stirring evenly, 105 ml of glycerol was added and the mixture was placed in a reaction vessel and hydrothermally reacted at 160℃ for 20 h. After washing, filtering and drying, zinc oxide nanorod materials were obtained.

[0043] S2, Surface sulfidation: The zinc oxide nanorods and thioacetamide from step S1 are dissolved in a mixed solution of ethanol and water in a 1:3 ratio at molar ratios of 1:1, 3:1, 6:1 and 12:1, respectively. The mixture is then stirred at 80°C for 3 hours. After washing, filtering and drying, zinc oxide material coated with zinc sulfide is obtained.

[0044] S3. Chemical Etching: The zinc sulfide-coated zinc oxide materials prepared in the four proportions of step S2 are uniformly dispersed in 400 mL of 1.5 mol / L ammonium chloride aqueous solution, and then stirred at 80 °C for 6 h. After washing, filtering, and drying, hollow zinc sulfide nanotube materials are obtained, such as... Figure 1 As shown;

[0045] The following steps illustrate the application of hollow zinc sulfide nanotubes in zinc-sulfur batteries:

[0046] S4. Mix the hollow zinc sulfide material obtained in step S3 with conductive carbon black and binder in a ratio of 7:2:1 to form a slurry, then coat it on the surface of the current collector, and after drying, it becomes the positive electrode sheet of the zinc-sulfur battery.

[0047] S5. Assemble a zinc-sulfur battery by combining the positive electrode obtained in step S4 with a zinc metal sheet, a separator, and an aqueous electrolyte.

[0048] Figure 1 This is a scanning electron microscope image of the hollow zinc sulfide nanotubes prepared in this embodiment. Figure 1Images (a), (b), (c), and (d) show hollow zinc sulfide nanotubes prepared from zinc oxide nanorods and thioacetamide at molar ratios of 1:1, 3:1, 6:1, and 12:1, respectively. Figure 1 It can be seen that the prepared hollow zinc sulfide nanotubes are all tubular structures with zinc sulfide on the outside and no solid filling inside. The tube length is about 500 nm to 3 μm, and the tube opening length is about 10 nm to 500 nm. From Figure 1 It can be clearly observed that as the ratio of zinc oxide nanorods to thioacetamide increases, the degree of damage to the resulting hollow zinc sulfide nanotubes also gradually increases. This indicates that as the ratio of the two increases, the outer layer of zinc sulfide formed by the zinc oxide nanorods sulfidated with the sulfiding agent becomes thinner, and etching the internal zinc oxide with an etchant at the same temperature and time will cause greater damage to the outer layer of zinc sulfide. Sulfur has a stable molecular structure, with electrons bound around atoms. When zinc sulfide is the cathode material, the chemical bond changes from a covalent bond to an ionic bond, improving conductivity. The hollow structure of the zinc sulfide in this invention also holds promise for optimizing ion transport pathways and accelerating reaction kinetics. Figure 1 It is evident that increasing the preparation ratio gradually decreases the length of the hollow zinc sulfide, reducing zinc sulfide aggregation and accelerating reaction kinetics. However, the increased degree of damage causes the originally continuous long hollow zinc sulfide nanotubes to disperse into smaller hollow zinc sulfide structures. These broken and miniaturized zinc sulfides agglomerate, which may also lead to slower kinetics. Simultaneously, the appropriate ratio of outer layer damage to the zinc sulfide and the hollow structure of the zinc sulfide can provide some space to mitigate the impact of volume changes caused by sulfur during charge and discharge. The electrode structure can be protected to some extent, improving the electrochemical activity of the positive electrode, thereby enhancing the cycle stability and lifespan of the aqueous zinc-sulfur battery.

[0049] Figure 2 This is a cycle performance test diagram of the zinc-sulfur battery assembled with hollow zinc sulfide as the positive electrode obtained in this embodiment; Figure 3 This is a rate performance test chart of a zinc-sulfur battery assembled using hollow zinc sulfide as the positive electrode, prepared in this embodiment. Figure 2 and Figure 3 It can be seen that zinc-sulfur batteries assembled with hollow zinc sulfide as the positive electrode exhibit good cycle performance and rate performance. However, zinc-sulfur batteries assembled with hollow zinc sulfide as the positive electrode at different ratios also show differences. Hollow zinc sulfide batteries prepared with ratios of 3:1 and 6:1 have moderate thickness and breakage, and smaller zinc sulfide aggregates, ensuring good stability and rate performance of the assembled batteries. Figure 2It can be seen that the initial discharge capacity of zinc-sulfur batteries assembled with hollow zinc sulfide as the positive electrode in four different ratios can reach a minimum of 324.9 mAh / g, and they can stably cycle 400 times at 0.5 A / g. This proves that the prepared hollow zinc sulfide can provide space for the volume change of sulfur during charge and discharge, thereby improving the battery's lifespan and stability. Figure 3 It is evident that zinc-sulfur batteries assembled using hollow zinc sulfide nanotubes prepared in 1:1 and 12:1 ratios as the positive electrode exhibit poor rate performance. The 1:1 ratio hollow zinc sulfide nanotubes have a more complete structure and a thicker outer zinc sulfide layer, resulting in more severe zinc sulfide aggregation and reduced electrochemical activity. The 12:1 ratio hollow zinc sulfide nanotubes are smaller and thinner, shortening the migration paths of ions and electrons and improving reaction kinetics. However, the aggregation of these miniaturized zinc sulfides leads to a decrease in conductivity, resulting in insufficient kinetics and consequently, even worse battery performance at high rates.

[0050] In summary, hollow zinc sulfide nanotubes prepared by zinc oxide nanorods and thioacetamide in an appropriate molar ratio can effectively address the issue of volume change, while also shortening the reaction path, improving electrical conductivity, and alleviating the problem of insufficient kinetics.

[0051] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. An application of hollow zinc sulfide nanotubes in aqueous zinc-sulfur batteries, characterized in that, The aqueous zinc-sulfur battery is assembled from hollow zinc sulfide nanotubes as the positive electrode, zinc metal sheets as the negative electrode, a separator, and an aqueous electrolyte; the preparation method of the hollow zinc sulfide nanotubes includes the following steps: S1, Preparation of zinc oxide nanorods: Zn-containing nanorods... 2+ The metal salt is dissolved in an aqueous solution of alkali metal hydroxide, stirred evenly, and then polyol organic solvent is added in proportion. The mixture is placed in a reaction vessel for hydrothermal reaction to obtain zinc oxide nanorods. S2, Surface sulfidation: Dissolve the zinc oxide nanorods and sulfiding agent from step S1 in a mixed solution of ethanol and water, and then stir at a certain temperature to carry out the sulfidation reaction to obtain zinc oxide material coated with zinc sulfide. S3. Chemical etching: The zinc sulfide-coated zinc oxide material from step S2 is uniformly dispersed in an aqueous etching agent solution, and then stirred at a certain temperature to carry out a chemical etching reaction to obtain hollow zinc sulfide nanotube material.

2. The application according to claim 1, characterized in that: The hollow zinc sulfide nanotubes are mixed with conductive carbon black and binder in a certain proportion to form a slurry, which is then coated on the surface of the current collector and dried to obtain the positive electrode sheet of the aqueous zinc-sulfur battery. The conductive carbon black is at least one of Super P, acetylene black, and Ketjen black. The binder is at least one of LA133, sodium alginate, PVDF, and PTFE. The current collector is at least one of stainless steel foil, stainless steel mesh, titanium foil, titanium mesh, carbon fiber cloth, carbon paper, and graphite paper.

3. The application according to claim 2, characterized in that: The mass ratio of the hollow zinc sulfide nanotubes to the conductive carbon black and binder is one of 9:0.5:0.5, 8:1:1, 7:2:1, and 6:3:

1.

4. The application according to claim 1, characterized in that: The diaphragm is at least one of glass fiber, non-woven fabric, and proton exchange membrane; The aqueous electrolyte is prepared by dissolving zinc metal salt in a deionized aqueous solution, with a concentration of 1~10 mol / L.

5. The application according to claim 4, characterized in that: The zinc metal salt is at least one of zinc sulfate, zinc chloride, zinc nitrate, zinc acetate, zinc perchlorate, zinc gluconate, zinc trifluoromethanesulfonate, and zinc bis(trifluoromethanesulfonyl)imide.

6. The application according to claim 1, characterized in that: In the method for preparing hollow zinc sulfide nanotubes, step S1 contains Zn. 2+ The metal salt is at least one selected from zinc acetate dihydrate, zinc nitrate hexahydrate, zinc chloride, zinc nitrate, and zinc sulfate; the Zn-containing... 2+ The molar concentration of the metal salt is 0.1~0.5 mol / L; In step S1, the alkali metal hydroxide is at least one of lithium hydroxide, sodium hydroxide, and potassium hydroxide; the molar concentration of the alkali metal hydroxide is 6~10 mol / L. In step S1, the polyol solvent is at least one of ethylene glycol, propylene glycol, and glycerol; the volume ratio between the polyol solvent and the aqueous solution is (2~5):

1. The hydrothermal reaction temperature in step S1 is 120~180℃, and the reaction time is 12~24h.

7. The application according to claim 1, characterized in that: In the method for preparing hollow zinc sulfide nanotubes, the sulfiding agent in step S2 is at least one of thioacetamide, thiourea, and sodium sulfide; the molar ratio between the added zinc oxide nanorods and the sulfiding agent is (1~12):

1. In step S2, the volume ratio of the ethanol and water mixture is 1:(2~4). In step S2, the temperature of the sulfidation reaction is 60~80℃, and the reaction time is 2~8h.

8. The application according to claim 1, characterized in that: In the method for preparing hollow zinc sulfide nanotubes, the chemical etching agent in step S3 is at least one of ammonia, ammonium chloride, sodium hydroxide, and potassium hydroxide; the molar concentration of the aqueous etching agent solution is 1~3 mol / L. In step S3, the temperature of the chemical etching reaction is 60~80℃, and the reaction time is 6~12h.

Images