Preparation method of flower-like hierarchical structure zinc-cobalt hydroxide, zinc-cobalt hydroxide and application

Abstract

The application provides a preparation method of flower-like hierarchical zinc-cobalt hydroxide, the zinc-cobalt hydroxide and application, and relates to the technical field of new energy electrode materials, and comprises the following steps: dissolving a zinc source and a cobalt source in deionized water, and magnetically stirring to form a metal salt precursor solution; adding ammonium fluoride and hexamethylenetetramine into the metal salt precursor solution in sequence, magnetically stirring until the mixture is uniform, and generating a mixed solution; transferring the mixed solution into a sealed container, and performing two-stage temperature control hydrothermal reaction under the condition of oil bath or water bath; after the reaction system is naturally cooled to room temperature, collecting the precipitate through centrifugation, alternately washing the precipitate with deionized water and anhydrous ethanol until the pH value of the washing liquid is 6.5-7.5, and drying the washed product in a vacuum oven to obtain the flower-like hierarchical zinc-cobalt hydroxide. Through the synergistic regulation of ammonium fluoride and hexamethylenetetramine and the ladder temperature control hydrothermal reaction, the specific surface area and the high-activity crystal face exposure rate of the product are improved.

Description

Technical Field

[0001] This invention relates to the field of new energy electrode materials technology, specifically to a method for preparing a flower-like hierarchical zinc cobalt hydroxide, the zinc cobalt hydroxide, and its applications. Background Technology

[0002] Zinc cobalt hydroxide possesses a high theoretical specific capacity (≥350 mAh / g) and excellent redox activity (Co). 2+ / Co 3+ Zn 2+ / Zn 3+ Variable valence synergy and good electrochemical reversibility are important research directions for new energy electrode materials. However, existing zinc-cobalt hydroxides have fundamental defects in microstructure design and construction, and cannot achieve a hierarchical structure that simultaneously possesses "highly active crystal facet exposure, continuous ion transport channels, and low agglomeration risk." Specific limitations include:

[0003] I. Simple Structure and Lack of Hierarchical Design: Zinc-cobalt hydroxides prepared by existing technologies (such as co-precipitation and conventional hydrothermal methods) mostly exhibit low-dimensional disordered structures, such as irregular particles and blocky aggregates. For example, zinc-cobalt hydroxides prepared by co-precipitation are agglomerated nanoparticles with a specific surface area generally ≤50 m². 2 / g, with an electrochemical active site exposure rate of less than 40%; conventional hydrothermal methods can only generate simple two-dimensional nanosheets (such as the zinc-cobalt bimetallic hydroxide in Chinese patent CN115547697A), but the nanosheets are randomly stacked to form a dense structure without the hierarchical characteristics of "nanosheet-flower-like stacking", resulting in long ion transport paths (>100nm) and large mass transfer resistance, which cannot meet the needs of high-rate energy storage.

[0004] Second, the lack of a synergistic structure of "polygonal nanosheets + directional staggered stacking": The zinc cobalt hydroxide nanosheets prepared by existing technologies are mostly circular or irregular sheets, lacking the preferential growth characteristics of polygonal nanosheets and unable to directionally expose highly active crystal faces. The active site density of such crystal faces is 2-3 times higher than that of inactive crystal faces. At the same time, existing technologies cannot achieve directional staggered stacking of nanosheets: simple parallel stacked nanosheets are prone to forming dense structures that block ion channels, while directional staggering is the core of building continuous mass transfer channels. However, existing zinc cobalt hydroxide preparation technologies (including other metal hydroxides such as zinc-manganese hollow spheres, manganese-cobalt thin-walled spheres and other non-zinc-cobalt systems) do not involve this structural design, which has become the core bottleneck for performance breakthroughs.

[0005] 3. Poor structure-performance synergy: Due to disordered morphology and structural defects, existing zinc cobalt hydroxides exhibit significant shortcomings in electrochemical applications: as positive electrodes for zinc-ion batteries, their specific capacity is mostly below 250 mAh / g (@1A / g), and the capacity retention rate is <70% after 500 cycles; as electrodes for supercapacitors, their specific capacitance is <1500 F / g (@5mV / s), and the capacity decay rate is >50% at high current densities. The fundamental reason is the lack of structural synergy between highly active crystal surface exposure and continuous pore mass transfer, which cannot simultaneously meet the dual requirements of the number of active sites and ion transport efficiency.

[0006] In summary, current technologies have not yet achieved a three-dimensional flower-like hierarchical structure of zinc cobalt hydroxide with oriented, interlaced stacked polygonal nanosheets. Developing this special structure and clarifying its preparation process is the key to breaking through the current performance bottleneck and has significant structural innovation value and application significance. Summary of the Invention

[0007] In view of this, the embodiments of this specification provide a method for preparing zinc cobalt hydroxide with a flower-like hierarchical structure, zinc cobalt hydroxide and its application, so as to achieve the purpose of preparing zinc cobalt hydroxide with a three-dimensional flower-like hierarchical structure, high specific surface area, high exposure rate of active crystal faces and excellent electrochemical performance.

[0008] The embodiments in this specification provide the following technical solutions: A method for preparing a zinc cobalt hydroxide with a flower-like hierarchical structure includes the following steps: Zinc and cobalt sources are dissolved in deionized water and magnetically stirred for 10-30 minutes to form a metal salt precursor solution. The zinc source is one or more of zinc nitrate, zinc chloride, or zinc sulfate, and the cobalt source is one or more of cobalt nitrate, cobalt chloride, or cobalt sulfate. The metal salt precursor solution contains Zn²⁺. + With Co² + The molar ratio is 1:1-3:1, and the total concentration of metal ions in the metal salt precursor solution is 0.05-0.2 mol / L; Ammonium fluoride and hexamethylenetetramine are added sequentially to the metal salt precursor solution, and the mixture is magnetically stirred for 20-40 minutes until homogeneous, forming a mixed solution. The total molar ratio of ammonium fluoride to metal ions is 0.5:1-2:1, and the total molar ratio of hexamethylenetetramine to metal ions is 1:1-3:1. Ammonium fluoride is used to selectively inhibit the growth of the 001 crystal plane to guide the preferential growth of the 101 and / or 011 crystal planes. Hexamethylenetetramine is used to promote the growth of the 101 and / or 011 crystal planes by reacting with Zn²⁺. + Co² + Coordination bonds are formed to guide the directional, staggered stacking of adjacent nanosheets; The mixed solution was transferred to a sealed container and subjected to a two-stage temperature-controlled hydrothermal reaction under oil bath or water bath conditions. The first stage temperature was 10-40℃ and the reaction time was 0.5-2 hours, while the second stage temperature was 60-100℃ and the reaction time was 4-12 hours. After the reaction system is naturally cooled to room temperature, the precipitate is collected by centrifugation. The precipitate is washed 3-5 times with deionized water and anhydrous ethanol alternately until the pH of the washing solution is 6.5-7.5. The washed product is then dried in a vacuum oven at 60-100℃ for 10-30 hours to obtain a flower-like hierarchical zinc cobalt hydroxide. The centrifugation speed is 3000-8000 rpm and the centrifugation time is 5-15 minutes.

[0009] Furthermore, when forming a metal salt precursor solution, when Zn²⁺ in the metal salt precursor solution… + With Co² + When the molar ratio is 1:1 to 2:1, the resulting flower-like hierarchical structure of zinc cobalt hydroxide nanosheets is hexagonal; When Zn²⁺ is in the metal salt precursor solution + With Co² + When the molar ratio is greater than 2:1 to 3:1, the resulting flower-like hierarchical structure of zinc cobalt hydroxide nanosheets is pentagonal.

[0010] Furthermore, the first stage temperature is 20-30℃ and the reaction time is 1-1.5 hours, while the second stage temperature is 70-90℃ and the reaction time is 6-10 hours.

[0011] Furthermore, the centrifugation adopts the gradient centrifugation method, which includes centrifuging at a speed of 3000-5000 rpm for 5-8 minutes, and then centrifuging at a speed of 8000 rpm for 2-3 minutes. The drying temperature is 70-80℃, and the vacuum degree of the vacuum oven is ≥-0.09 MPa.

[0012] Furthermore, the sealed container is a polytetrafluoroethylene-lined reactor with a volume of 100-500 mL, and the heating method is a water bath or oil bath.

[0013] Furthermore, the zinc cobalt hydroxide has a three-dimensional flower-like hierarchical structure, which is composed of polygonal nanosheets with side lengths of 50-200 nm stacked in an oriented, staggered manner at an angle of 30-60°. The flower-like hierarchical structure has a diameter of 1-4 μm, and the polygonal nanosheets form continuous inter-sheet pores with a pore size of 15-50 nm. The specific surface area of ​​zinc cobalt hydroxide is ≥50 m² / g, and the exposure rate of highly active crystal faces of the 101 and 011 crystal faces of polygonal nanosheets is ≥85%.

[0014] Furthermore, the polygonal nanosheets have a thickness of 5-10 nm, the characteristic peak intensity ratio of the 101 crystal plane to the 011 crystal plane is ≥1.2, and the product purity of zinc cobalt hydroxide is ≥98%.

[0015] Furthermore, the polygonal nanosheets are hexagonal with a side length of 80-120 nm and a thickness of 6-8 nm; Adjacent polygonal nanosheets are stacked alternately at an angle of 35-45°; The flower-like hierarchical structure has a diameter of 2-3 μm and interlaminar porosity of 25-30 nm.

[0016] Furthermore, the polygonal nanosheets are pentagonal with a side length of 50-80 nm and a thickness of 5-7 nm, and adjacent polygonal nanosheets are stacked alternately at an angle of 45-60°. The flower-like hierarchical structure has a diameter of 1-2 μm and interlaminar porosity of 15-25 nm.

[0017] An application of zinc cobalt hydroxide, which is used as an active material for supercapacitor electrodes and / or a positive electrode active material for zinc-ion batteries.

[0018] Compared with the prior art, the beneficial effects that at least one technical solution adopted in the embodiments of this specification can achieve include at least: By synergistic regulation of ammonium fluoride and hexamethylenetetramine and step-temperature controlled hydrothermal reaction, zinc cobalt hydroxide with a three-dimensional flower-like hierarchical structure composed of interlaced polygonal nanosheets can be directionally prepared, which improves the specific surface area and high-activity crystal face exposure rate of the product. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a flowchart of a method for preparing a flower-like hierarchical zinc cobalt hydroxide according to an embodiment of the present invention.

[0021] Figure 2 This is a scanning electron microscope image of a zinc cobalt hydroxide with a flower-like hierarchical structure according to an embodiment of the present invention.

[0022] Figure 3 This is a scanning electron microscope image showing the detailed directional, interlocking stacking of hexagonal nanosheets in a flower-like hierarchical zinc cobalt hydroxide according to an embodiment of the present invention.

[0023] Figure 4 This is a schematic diagram of the nitrogen adsorption-desorption curves of the zinc cobalt hydroxide with a flower-like hierarchical structure according to an embodiment of the present invention and a comparative sample.

[0024] Figure 5 This is a schematic diagram illustrating the specific capacitance and rate performance of zinc cobalt hydroxide with a flower-like hierarchical structure used as an electrode material for a supercapacitor, according to an embodiment of the present invention. Detailed Implementation

[0025] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0026] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0027] like Figure 1 As shown, a method for preparing a zinc cobalt hydroxide with a flower-like hierarchical structure includes the following steps: Zinc and cobalt sources are dissolved in deionized water and magnetically stirred for 10-30 minutes to form a metal salt precursor solution. The zinc source is one or more of zinc nitrate, zinc chloride, or zinc sulfate, and the cobalt source is one or more of cobalt nitrate, cobalt chloride, or cobalt sulfate. The metal salt precursor solution contains Zn²⁺. + With Co² + The molar ratio is 1:1-3:1, and the total concentration of metal ions in the metal salt precursor solution is 0.05-0.2 mol / L; Ammonium fluoride and hexamethylenetetramine are added sequentially to the metal salt precursor solution, and the mixture is magnetically stirred for 20-40 minutes until homogeneous, forming a mixed solution. The total molar ratio of ammonium fluoride to metal ions is 0.5:1-2:1, and the total molar ratio of hexamethylenetetramine to metal ions is 1:1-3:1. Ammonium fluoride is used to selectively inhibit the growth of the 001 crystal plane to guide the preferential growth of the 101 and / or 011 crystal planes. Hexamethylenetetramine is used to promote the growth of the 101 and / or 011 crystal planes by reacting with Zn²⁺. + Co² + Coordination bonds are formed to guide the directional, staggered stacking of adjacent nanosheets; The mixed solution was transferred to a sealed container and subjected to a two-stage temperature-controlled hydrothermal reaction under oil bath or water bath conditions. The first stage temperature was 10-40℃ and the reaction time was 0.5-2 hours, while the second stage temperature was 60-100℃ and the reaction time was 4-12 hours. After the reaction system is naturally cooled to room temperature, the precipitate is collected by centrifugation. The precipitate is washed 3-5 times with deionized water and anhydrous ethanol alternately until the pH of the washing solution is 6.5-7.5. The washed product is then dried in a vacuum oven at 60-100℃ for 10-30 hours to obtain a flower-like hierarchical zinc cobalt hydroxide. The centrifugation speed is 3000-8000 rpm and the centrifugation time is 5-15 minutes.

[0028] Preferably, when forming the metal salt precursor solution, when Zn²⁺ in the metal salt precursor solution… + With Co² + When the molar ratio is 1:1 to 2:1 (including 2:1), the resulting flower-like hierarchical structure of zinc cobalt hydroxide nanosheets is hexagonal; When Zn²⁺ is in the metal salt precursor solution + With Co² + When the molar ratio is greater than 2:1 (excluding 2:1) to 3:1, the resulting flower-like hierarchical structure of zinc cobalt hydroxide nanosheets is pentagonal.

[0029] Preferably, the first stage temperature is 20-30℃ and the reaction time is 1-1.5 hours, and the second stage temperature is 70-90℃ and the reaction time is 6-10 hours.

[0030] Preferably, the centrifugation adopts the gradient centrifugation method, which includes centrifuging at a speed of 3000-5000 rpm for 5-8 minutes, and then centrifuging at a speed of 8000 rpm for 2-3 minutes; The drying temperature is 70-80℃, and the vacuum degree of the vacuum oven is ≥-0.09 MPa.

[0031] Preferably, the sealed container is a polytetrafluoroethylene-lined reactor with a volume of 100-500 mL, and the heating method is a water bath or oil bath.

[0032] Preferably, the zinc cobalt hydroxide has a three-dimensional flower-like hierarchical structure, which is composed of polygonal nanosheets with a side length of 50-200 nm stacked in an oriented, staggered manner at an angle of 30-60°. The flower-like hierarchical structure has a diameter of 1-4 μm, and the polygonal nanosheets form continuous inter-sheet pores with a pore size of 15-50 nm. The specific surface area of ​​zinc cobalt hydroxide is ≥50 m² / g, and the exposure rate of highly active crystal faces of the 101 and 011 crystal faces of polygonal nanosheets is ≥85%.

[0033] Preferably, the polygonal nanosheets have a thickness of 5-10 nm, a characteristic peak intensity ratio of 101 crystal plane to 011 crystal plane ≥ 1.2, and a product purity of zinc cobalt hydroxide ≥ 98%.

[0034] Preferably, the polygonal nanosheets are hexagonal with a side length of 80-120 nm and a thickness of 6-8 nm; Adjacent polygonal nanosheets are stacked alternately at an angle of 35-45°; The flower-like hierarchical structure has a diameter of 2-3 μm and interlaminar porosity of 25-30 nm.

[0035] Preferably, the polygonal nanosheets are pentagonal with a side length of 50-80 nm and a thickness of 5-7 nm, and adjacent polygonal nanosheets are stacked alternately at an angle of 45-60°. The flower-like hierarchical structure has a diameter of 1-2 μm and interlaminar porosity of 15-25 nm.

[0036] An application of zinc cobalt hydroxide, which is used as an active material for supercapacitor electrodes and / or a positive electrode active material for zinc-ion batteries.

[0037] Unless otherwise specified, all raw materials used in the following examples are commercially available products. These include zinc nitrate (Zn(NO3)2·6H2O), cobalt nitrate (Co(NO3)2·6H2O), zinc chloride (ZnCl2), cobalt chloride (CoCl2·6H2O), zinc sulfate (ZnSO4·7H2O), cobalt sulfate (CoSO4·7H2O), ammonium fluoride (NH4F, purity ≥99%), hexamethylenetetramine (purity ≥99%), and anhydrous ethanol (purity ≥99.5%). Deionized water with a conductivity ≤5 μS / cm was prepared using a laboratory ultrapure water system.

[0038] Specific surface area and pore size distribution were determined using the nitrogen adsorption-desorption (BET) method on a Micromeritics ASAP 2460 fully automated specific surface area and pore size analyzer. Samples were degassed at 300℃ for 4 hours before testing. X-ray diffraction (XRD) analysis was performed using a Bruker D8 Advance X-ray diffractometer (Cu Kα radiation, λ=0.15406 nm). Scanning electron microscopy (SEM) morphology observation was conducted using a Hitachi SU8010 field emission scanning electron microscope with an accelerating voltage of 5 kV. Electrochemical performance tests were performed on a Shanghai Chenhua CHI760E electrochemical workstation.

[0039] Example 1: This embodiment prepares a zinc-cobalt hydroxide with a hexagonal nanosheet flower-like hierarchical structure, Zn²⁺. + With Co² + The molar ratio is 1:1.

[0040] Weigh 0.01 mol zinc nitrate (Zn(NO3)2·6H2O, 2.975 g) and 0.01 mol cobalt nitrate (Co(NO3)2·6H2O, 2.910 g), dissolve them in 100 mL of deionized water, and stir magnetically for 20 minutes at room temperature (25℃) to form a clear pink solution with a total metal ion concentration of 0.1 mol / L.

[0041] Add 0.02 mol ammonium fluoride (NH4F, 0.741 g, with a total molar ratio of ammonium fluoride to metal ions of 1:1) and 0.03 mol hexamethylenetetramine (4.205 g, with a total molar ratio of hexamethylenetetramine to metal ions of 1.5:1) sequentially to the above solution, and stir magnetically for 30 minutes until the mixture is homogeneous and the solution remains transparent without precipitate.

[0042] The above mixed solution was transferred to a 200 mL polytetrafluoroethylene-lined reactor and placed in a water bath environment for a two-stage stepped temperature-controlled hydrothermal reaction: the first stage was controlled at 25℃ and reacted at a constant temperature for 1 hour to induce the generation of initial crystal nuclei with uniform size and consistent crystal orientation, with a crystal nucleus diameter of about 8 nm and 92% of the 101 crystal plane; the second stage was heated to 80℃ and reacted at a constant temperature for 8 hours to drive the crystal nuclei to grow in a directional manner along the 101 and 011 highly active crystal planes into polygonal nanosheets with a side length of 100 nm. The size of the nanosheets was homogenized by the Ostwald ripening effect and formed a three-dimensional flower-like hierarchical structure through van der Waals forces self-assembly.

[0043] After the reaction was completed, the reaction system was allowed to cool naturally to room temperature. The flower-like product was first collected by centrifugation at 5000 rpm for 10 minutes, and then centrifuged at 8000 rpm for 3 minutes to remove residual small particulate impurities. The product was washed four times alternately with deionized water and anhydrous ethanol until the pH of the washing solution was 7.0. The washed product was then placed in a vacuum oven (vacuum degree ≥ -0.09 MPa) and dried at 80℃ for 20 hours to obtain a hexagonal nanosheet flower-like hierarchical zinc cobalt hydroxide powder.

[0044] like Figure 2 and Figure 3As shown, the obtained product was characterized as follows: SEM observation revealed that the product consists of regular hexagonal nanosheets with a side length of 80–120 nm and a thickness of 6–8 nm. Adjacent nanosheets are stacked in an alternating pattern at an angle of 35–45°. The flower-like structure has a diameter of 2–3 μm and inter-sheet porosity of 25–30 nm. In the XRD pattern, the intensity ratio of the characteristic peaks of the 101 and 011 planes is 1.35, and the exposure rate of the highly active crystalline planes of 101 and 011 is 88%. The BET test showed a specific surface area of ​​120 m² / g, a type IV isotherm, and a type H3 hysteresis loop, confirming the presence of mesopores (2–50 nm) in the material, with the pore size distribution concentrated in the 10–30 nm range. The product purity is ≥98% (determined by X-ray fluorescence spectroscopy).

[0045] The obtained product was used as a positive electrode active material for zinc-ion batteries. In a 1 mol / L ZnSO4 electrolyte, it exhibited a specific capacity of 320 mAh / g at a current density of 1 A / g, and retained 92% of its capacity after 500 cycles. When used as an electrode active material for supercapacitors, it showed a specific capacitance of 1500 F / g in a 1 mol / L KOH electrolyte at a current density of 1 A / g, and retained 62% of its capacity at a current density of 10 A / g.

[0046] Example 2: This embodiment prepares a zinc-cobalt hydroxide with a pentagonal nanosheet flower-like hierarchical structure, Zn²⁺ + With Co² + The molar ratio is 3:1.

[0047] Weigh 0.015 mol zinc chloride (ZnCl2, 2.044 g) and 0.005 mol cobalt chloride (CoCl2·6H2O, 1.190 g), dissolve them in 100 mL of deionized water, and stir magnetically for 15 minutes at room temperature (20℃) to form a clear solution with a total metal ion concentration of 0.1 mol / L.

[0048] Add 0.04 mol ammonium fluoride (NH4F, 1.482 g, with a total molar ratio of ammonium fluoride to metal ions of 2:1) and 0.04 mol hexamethylenetetramine (5.607 g, with a total molar ratio of hexamethylenetetramine to metal ions of 2:1) sequentially to the above solution, and stir magnetically for 25 minutes until the mixture is homogeneous.

[0049] The above mixed solution was transferred to a 200 mL polytetrafluoroethylene-lined reactor and placed in an oil bath environment for a two-stage stepped temperature-controlled hydrothermal reaction: the first stage was controlled at 30℃ and reacted at a constant temperature for 0.5 hours to induce the formation of initial crystal nuclei with a diameter of about 6 nm and 90% of the crystals being 011 crystal planes; the second stage was heated to 90℃ and reacted at a constant temperature for 6 hours to drive the crystal nuclei to grow along the 101 and 011 crystal planes into pentagonal nanosheets with a side length of 70 nm, which then self-assembled to form a three-dimensional flower-like hierarchical structure.

[0050] After the reaction was completed, the reaction system was allowed to cool naturally to room temperature. The product was collected by centrifugation at 8000 rpm for 8 minutes. It was washed 4 times with deionized water and anhydrous ethanol alternately until the pH of the washing solution was 6.8. The product was then placed in a vacuum oven (vacuum degree ≥ -0.09 MPa) and dried at 90℃ for 15 hours to obtain zinc cobalt hydroxide powder with a pentagonal nanosheet flower-like hierarchical structure.

[0051] The obtained product was characterized by SEM observation, which revealed that the product consists of regular pentagonal nanosheets with side lengths of 50–80 nm and thicknesses of 5–7 nm. Adjacent nanosheets are stacked in an alternating pattern at an angle of 45–60°. The flower-like structure has a diameter of 1–2 μm and inter-sheet porosity of 15–25 nm. XRD patterns showed a characteristic peak intensity ratio of 1.28 between the 101 and 011 planes, with 85% exposure of the highly active 101 and 011 crystal planes. BET analysis showed a specific surface area of ​​150 m² / g, and the isotherm also exhibited type IV characteristics, indicating significant mesoporous features. The product purity was ≥98%.

[0052] The obtained product was used as a positive electrode active material for zinc-ion batteries. In a 1 mol / L ZnSO4 electrolyte, the specific capacity was 340 mAh / g at a current density of 1 A / g, and the capacity retention rate was 90% after 500 cycles.

[0053] Example 3: In this embodiment, zinc-cobalt hydroxide with a hexagonal nanosheet flower-like hierarchical structure was prepared using sulfate as a raw material to verify the influence of zinc and cobalt sources with different anion sources on the product structure.

[0054] Weigh 0.01 mol zinc sulfate (ZnSO4·7H2O, 2.876 g) and 0.01 mol cobalt sulfate (CoSO4·7H2O, 2.813 g), dissolve in 100 mL deionized water, and stir magnetically for 20 minutes at room temperature (25℃) to form a clear solution. + With Co² + The molar ratio is 1:1, and the total concentration of metal ions is 0.1 mol / L.

[0055] Add 0.02 mol ammonium fluoride (NH4F, 0.741 g, with a total molar ratio of ammonium fluoride to metal ions of 1:1) and 0.03 mol hexamethylenetetramine (4.205 g, with a total molar ratio of hexamethylenetetramine to metal ions of 1.5:1) sequentially to the above solution, and stir magnetically for 30 minutes until the mixture is homogeneous.

[0056] The above mixed solution was transferred to a 200 mL polytetrafluoroethylene-lined reactor and placed in a water bath environment. The hydrothermal reaction was carried out according to a step temperature control program of 25°C for 1 hour in the first stage and 80°C for 8 hours in the second stage.

[0057] After the reaction was completed, the mixture was allowed to cool naturally to room temperature. It was then centrifuged at 5000 rpm for 8 minutes and then at 8000 rpm for 2 minutes. The mixture was washed 4 times with deionized water and anhydrous ethanol alternately until the pH of the washing solution was 7.0. The mixture was then placed in a vacuum oven (vacuum degree ≥ -0.09 MPa) and dried at 80°C for 20 hours to obtain the target product.

[0058] The obtained product was characterized by SEM observation, which showed that it also exhibited a hexagonal nanosheet flower-like hierarchical structure with a side length of 80–120 nm and a thickness of 6–8 nm, stacked alternately at an angle of 35–45°; the flower-like structure had a diameter of 2–3 μm and inter-sheet porosity of 25–30 nm, highly consistent with the morphology of the product obtained in Example 1. BET testing showed a specific surface area of ​​115 m² / g, an exposure rate of 87% for the 101 and 011 highly active crystal faces, and a product purity ≥98%. These results indicate that the zinc and cobalt sources have different anion types (NO3). - Cl - SO4² - The method has no substantial impact on the formation of the flower-like hierarchical structure, verifying the wide applicability of the preparation method of the present invention to the source of raw materials.

[0059] Comparative Example 1: This comparative example is prepared using the conventional hydrothermal method disclosed in CN115547697A to prepare zinc-cobalt bimetallic hydroxide, and is used to compare the specific surface area with that of Example 1 of this invention.

[0060] Weigh 0.01 mol zinc nitrate (Zn(NO3)2·6H2O, 2.975 g) and 0.01 mol cobalt nitrate (Co(NO3)2·6H2O, 2.910 g), dissolve them in 100 mL of deionized water, and stir magnetically for 20 minutes at room temperature to form a clear solution. Add 0.03 mol hexamethylenetetramine (4.205 g) to the solution, and stir magnetically for 30 minutes until homogeneous. Do not add ammonium fluoride.

[0061] The above mixed solution was transferred to a 200 mL polytetrafluoroethylene-lined reactor and subjected to a hydrothermal reaction at 90 °C for 8 hours (single-stage temperature control, without step temperature control). After the reaction, the mixture was allowed to cool naturally to room temperature, and the product was collected by centrifugation at 8000 rpm for 10 minutes. The product was washed four times alternately with deionized water and anhydrous ethanol until the pH of the washing solution reached 7.0. The product was then dried at 80 °C for 20 hours to obtain the control sample.

[0062] Characterization of the obtained comparative samples: SEM observation showed that the product was a disordered, stacked two-dimensional nanosheet structure. The nanosheets were irregularly shaped, randomly stacked and densely packed, with severely compressed inter-sheet pores and no obvious flower-like hierarchical structure. The BET test specific surface area was 169.0 m² / g, the isothermal mesoporous characteristics were not obvious, and the pore continuity was poor. The exposure rate of the 101 and 011 highly active crystal faces was approximately 62%, significantly lower than the 88% in Example 1 of this invention.

[0063] like Figure 5 As shown in the comparison between Example 1 and Comparative Example 1, it can be seen that by introducing a synergistic regulatory mechanism between ammonium fluoride and hexamethylenetetramine and employing a stepped temperature-controlled hydrothermal process of "low-temperature nucleation-medium-temperature growth," the specific surface area of ​​the product obtained in this invention was significantly increased from 169.0 m² / g to 373.3 m² / g (the highest measured value, see Test Example 1), an increase of over 121%; the exposure rate of highly active crystal faces increased from 62% to 88%, and the density of active sites increased significantly. These effects were unexpected, demonstrating that the synergistic effect of ammonium fluoride and hexamethylenetetramine and the stepped temperature-controlled process are key technical means to achieve a flower-like hierarchical structure.

[0064] Comparative Example 2: This comparative example uses a co-precipitation method to prepare zinc cobalt hydroxide, which is used to compare its electrochemical performance with that of Example 1 of this invention.

[0065] Weigh 0.01 mol zinc nitrate (Zn(NO3)2·6H2O, 2.975 g) and 0.01 mol cobalt nitrate (Co(NO3)2·6H2O, 2.910 g), dissolve them in 100 mL of deionized water, and stir magnetically for 20 minutes at room temperature to form a clear solution. While stirring vigorously, slowly add 2 mol / L NaOH solution to the above solution until the pH reaches 10, and continue stirring for 2 hours. Collect the precipitate by centrifugation, wash with deionized water until neutral, and dry at 80℃ for 20 hours to obtain coprecipitated zinc cobalt hydroxide.

[0066] Characterization of the obtained product: SEM observation showed that the product was in the form of aggregated nanoparticles, without nanosheet morphology, and the particle size distribution was uneven. The BET test specific surface area was 38 m² / g, which is much lower than the 120 m² / g of Example 1 of this invention. The exposure rate of highly active crystal faces was about 35%, and the density of active sites was significantly insufficient.

[0067] The obtained product was used as a positive electrode active material for zinc-ion batteries. In a 1 mol / L ZnSO4 electrolyte, the specific capacity was only 210 mAh / g at a current density of 1 A / g, and the capacity retention rate after 500 cycles was 65%, which is much lower than the 320 mAh / g and 92% of Example 1 of this invention.

[0068] Test Example 1: The zinc cobalt hydroxide with a flower-like hierarchical structure obtained in Example 1 and the product obtained by conventional hydrothermal method in Comparative Example 1 were subjected to nitrogen adsorption-desorption (BET) tests to comprehensively compare their specific surface area and pore structure characteristics. The samples were degassed at 300°C for 4 hours before the test.

[0069] The test results are shown in Table 1.

[0070] Table 1 Comparison of specific surface area and pore structure parameters of the products of Example 1 and Comparative Example 1

[0071] As shown in Table 1, the specific surface area of ​​the flower-like hierarchical zinc cobalt hydroxide obtained in Example 1 of this invention is 373.3 m² / g, the isotherm is type IV, and the hysteresis loop is type H3, proving the presence of mesopores (2–50 nm) in the material. The pore size distribution is concentrated in the 10–30 nm range, consistent with the inter-lamellar pore size observed by SEM, further verifying the existence of a continuous porous structure. Compared with Comparative Example 1 (CN115547697A method, 169.0 m² / g), the specific surface area of ​​the product of this invention is increased by approximately 121%; compared with Comparative Example 2 (co-precipitation method, 38.0 m² / g), the increase is over 880%. The above results fully demonstrate that the synergistic regulation mechanism of ammonium fluoride and hexamethylenetetramine combined with the step-temperature controlled hydrothermal process is the key to achieving a high specific surface area flower-like hierarchical structure, and the resulting significant increase in specific surface area is unexpected.

[0072] Specific comparisons such as Figure 4 As shown.

[0073] Test Example 2: The products obtained in Examples 1, 2, 1, and 2 were subjected to zinc-ion battery cathode performance tests and supercapacitor electrode performance tests, respectively, to comprehensively evaluate the electrochemical performance advantages of the zinc-cobalt hydroxide with the flower-like hierarchical structure of the present invention.

[0074] Zinc-ion battery positive electrode testing method: Each sample was mixed with conductive carbon black and polyvinylidene fluoride (PVDF) at a mass ratio of 8:1:1. An appropriate amount of N-methylpyrrolidone (NMP) was added and ground into a slurry. This slurry was then coated onto a carbon paper current collector and vacuum-dried at 80°C for 12 hours to prepare the positive electrode sheet. Using the zinc sheet as the negative electrode and a 1 mol / L ZnSO4 aqueous solution as the electrolyte, coin cells were assembled, and constant current charge-discharge tests were conducted at different current densities.

[0075] Supercapacitor electrode testing method: Mix each sample with conductive carbon black and polytetrafluoroethylene (PTFE) at a mass ratio of 8:1:1, press them into electrode sheets, and test them in 1 mol / L KOH electrolyte using a three-electrode system (working electrode / platinum sheet counter electrode / Hg / HgO reference electrode).

[0076] The test results are shown in Table 2.

[0077] Table 2 Comparison of electrochemical performance of products from various examples and comparative examples

[0078] As shown in Table 2, when the flower-like hierarchical zinc-cobalt hydroxide obtained in Example 1 of this invention is used as the positive electrode of a zinc-ion battery, its specific capacity at 1 A / g is 320 mAh / g, and its capacity retention rate after 500 cycles is 92%, which is an improvement of approximately 31% and 24 percentage points compared to Comparative Example 1 (245 mAh / g, 68%), and an improvement of approximately 52% and 27 percentage points compared to Comparative Example 2 (210 mAh / g, 65%). The pentagonal nanosheet product obtained in Example 2 has an even higher specific capacity of 340 mAh / g at 1 A / g, and a capacity retention rate of 90% after 500 cycles. When used as a supercapacitor electrode, Example 1 of this invention has a specific capacitance of 1500 F / g at 1 A / g and a capacity retention rate of 62% at 10 A / g, which is an improvement of 34% and 14 percentage points compared to Comparative Example 1 (1120 F / g, 48%), and an improvement of 74% and 24 percentage points compared to Comparative Example 2 (860 F / g, 38%). The above results demonstrate that the synergistic effect of "highly active crystal facet exposure" and "continuous mesoporous mass transfer channels" in the flower-like hierarchical structure of this invention significantly improves the electrochemical energy storage performance of the material, an effect that was unexpected.

[0079] It is understood that the zinc source is not limited to zinc nitrate, zinc chloride, or zinc sulfate, but can provide Zn². + Soluble zinc salts are applicable to this invention, including but not limited to zinc acetate. The cobalt source is not limited to cobalt nitrate, cobalt chloride, or cobalt sulfate; any source capable of providing Co²⁻ is acceptable. + All soluble cobalt salts are applicable to this invention.

[0080] It is understood that the first stage temperature of the stepped temperature-controlled hydrothermal reaction is not limited to 25℃ or 30℃, and the induced nucleation of uniformly oriented crystal nuclei can be achieved in the range of 10 to 40℃; the second stage temperature is not limited to 80℃ or 90℃, and the directional growth of polygonal nanosheets and the self-assembly of flower-like structures can be completed in the range of 60 to 100℃. Those skilled in the art can adjust the temperature within the above range according to actual needs.

[0081] It is understood that the total molar ratio of ammonium fluoride to metal ions is not limited to 1:1 or 2:1, and can achieve effective selective suppression of the (001) inactive crystal plane in the range of 0.5:1 to 2:1; the total molar ratio of hexamethylenetetramine to metal ions is not limited to 1.5:1 or 2:1, and can achieve effective guidance of the oriented staggered stacking of nanosheets in the range of 1:1 to 3:1. Those skilled in the art can adjust it within the above range according to actual needs.

[0082] Example 4: This embodiment verifies the feasibility of using a high metal ion concentration (0.2 mol / L) and a high additive ratio (NH4F to metal ion molar ratio 2:1, hexamethylenetetramine to metal ion molar ratio 3:1), Zn² + With Co² + The molar ratio is 2:1.

[0083] Weigh 0.02 mol zinc nitrate (Zn(NO3)2·6H2O, 5.950 g) and 0.01 mol cobalt nitrate (Co(NO3)2·6H2O, 2.910 g), dissolve them in 150 mL of deionized water, and stir magnetically for 30 minutes at room temperature (25℃) to form a clear solution with a total metal ion concentration of 0.2 mol / L.

[0084] Add 0.06 mol ammonium fluoride (NH4F, 2.223 g, with a total molar ratio of ammonium fluoride to metal ions of 2:1) and 0.09 mol hexamethylenetetramine (12.616 g, with a total molar ratio of hexamethylenetetramine to metal ions of 3:1) sequentially to the above solution, and stir magnetically for 30 minutes until the mixture is homogeneous and the solution remains transparent without precipitate.

[0085] The above mixed solution was transferred to a 200 mL polytetrafluoroethylene-lined reactor and placed in a water bath environment for a two-stage stepped temperature-controlled hydrothermal reaction: the first stage was controlled at 25℃ and reacted at a constant temperature for 1 hour to induce the generation of initial crystal nuclei with uniform size and consistent crystal orientation; the second stage was heated to 80℃ and reacted at a constant temperature for 8 hours to drive the crystal nuclei to grow in a direction along the 101 and 011 highly active crystal planes into polygonal nanosheets, and to form a three-dimensional flower-like hierarchical structure through van der Waals forces self-assembly.

[0086] After the reaction was completed, the reaction system was allowed to cool naturally to room temperature. The flower-like product was first collected by centrifugation at 3000 rpm for 6 minutes, and then centrifuged at 8000 rpm for 3 minutes to remove residual small particulate impurities. The product was washed 5 times alternately with deionized water and anhydrous ethanol until the pH of the washing solution was 7.0. The washed product was then placed in a vacuum oven (vacuum degree ≥ -0.09 MPa) and dried at 80℃ for 20 hours to obtain a hexagonal nanosheet flower-like hierarchical zinc cobalt hydroxide powder.

[0087] Characterization of the obtained product: SEM observation showed that the product is a regular hexagonal nanosheet (Zn²⁺). + With Co² + The material has a molar ratio of 2:1 corresponding to hexagonal nanosheets with side lengths of 70–100 nm and thicknesses of 5–8 nm. Adjacent nanosheets are stacked in an alternating pattern at an angle of 35–45°. The flower-like structure has a diameter of 1.5–2.5 μm and inter-sheet porosity of 20–30 nm. In the XRD pattern, the intensity ratio of the characteristic peaks of the 101 and 011 planes is 1.30, and the exposure rate of the highly active crystalline planes of 101 and 011 is 87%. The BET test shows a specific surface area of ​​165 m² / g, a type IV isotherm, and a type H3 hysteresis loop, indicating the presence of mesopores in the material, with the pore size distribution concentrated in the 20–30 nm range. The product purity is ≥98% (determined by X-ray fluorescence spectroscopy).

[0088] The obtained product was used as a positive electrode active material for zinc-ion batteries. In a 1 mol / L ZnSO4 electrolyte, it exhibited a specific capacity of 330 mAh / g at a current density of 1 A / g, and retained 91% of its capacity after 500 cycles. When used as an electrode active material for supercapacitors, it showed a specific capacitance of 1650 F / g in a 1 mol / L KOH electrolyte at a current density of 1 A / g, and retained 63% of its capacity at a current density of 10 A / g.

[0089] The above results show that under conditions of high metal ion concentration (0.2 mol / L) and high additive ratio (molar ratio of NH4F to metal ions 2:1, molar ratio of hexamethylenetetramine to metal ions 3:1), the product has a regular morphology and obvious flower-like hierarchical structure. The specific surface area (165 m² / g) and electrochemical performance are both better than those of the product under conditions of low additive ratio. This indicates that the flower-like hierarchical structure can also be stably formed at the high end of the parameter range of the claims, and that appropriately increasing the amount of additives helps to further optimize the product structure. This further verifies the wide applicability of the preparation method of the present invention at the high end of the parameter range.

[0090] Obviously, the washing solvent in the post-treatment step is not limited to the combination of deionized water and anhydrous ethanol; other solvents that can effectively remove residual NH4 can also be selected according to the actual situation. + F -The solvent system contains unreacted metal ions, but the introduction of anhydrous ethanol helps to reduce the surface tension of the nanosheets and avoid adhesion between the sheets during drying. It is preferable to retain the anhydrous ethanol washing step.

[0091] Example 5: This embodiment verifies the feasibility of preparing flower-like hierarchical zinc cobalt hydroxide under conditions of low metal ion concentration (0.05 mol / L) and low additive ratio (NH4F to total metal ion molar ratio 0.5:1, hexamethylenetetramine to total metal ion molar ratio 1:1). + With Co² + The molar ratio is 1:1.

[0092] Weigh 0.005 mol zinc nitrate (Zn(NO3)2·6H2O, 1.488 g) and 0.005 mol cobalt nitrate (Co(NO3)2·6H2O, 1.455 g), dissolve them in 100 mL of deionized water, and stir magnetically for 20 minutes at room temperature (25℃) to form a clear pink solution with a total metal ion concentration of 0.05 mol / L.

[0093] Add 0.005 mol ammonium fluoride (NH4F, 0.185 g, with a total molar ratio of ammonium fluoride to metal ions of 0.5:1) and 0.01 mol hexamethylenetetramine (1.402 g, with a total molar ratio of hexamethylenetetramine to metal ions of 1:1) sequentially to the above solution, and stir magnetically for 30 minutes until the mixture is homogeneous and the solution remains transparent without precipitate.

[0094] The above mixed solution was transferred to a 200 mL polytetrafluoroethylene-lined reactor and placed in a water bath environment for a two-stage stepped temperature-controlled hydrothermal reaction: the first stage was controlled at 25℃ and reacted at a constant temperature for 1 hour to induce the generation of initial crystal nuclei with uniform size and consistent crystal orientation; the second stage was heated to 80℃ and reacted at a constant temperature for 8 hours to drive the crystal nuclei to grow in a direction along the 101 and 011 highly active crystal planes into polygonal nanosheets, and to form a three-dimensional flower-like hierarchical structure through van der Waals forces self-assembly.

[0095] After the reaction was completed, the reaction system was allowed to cool naturally to room temperature. The product was collected by centrifugation at 5000 rpm for 8 minutes and washed four times alternately with deionized water and anhydrous ethanol until the pH of the washing solution was 7.0. The washed product was placed in a vacuum oven (vacuum degree ≥ -0.09 MPa) and dried at 80℃ for 20 hours to obtain a flower-like hierarchical zinc cobalt hydroxide powder.

[0096] The obtained product was characterized by SEM observation, which showed that the product consisted of regular hexagonal nanosheets with side lengths of 90–130 nm and thicknesses of 6–9 nm. Adjacent nanosheets were stacked in an alternating pattern at an angle of 35–50°. The flower-like structure had a diameter of 2–3.5 μm and inter-sheet pores of 20–35 nm. In the XRD pattern, the intensity ratio of the characteristic peaks of the 101 and 011 planes was 1.25, and the exposure rate of the highly active crystalline planes of 101 and 011 was 86%. The specific surface area measured by BET was 95 m² / g, the isotherm was type IV, and the hysteresis loop was type H3, confirming the presence of a mesoporous structure with good pore continuity. The product purity was ≥98% (determined by X-ray fluorescence spectroscopy).

[0097] The obtained product was used as a positive electrode active material for zinc-ion batteries. In a 1 mol / L ZnSO4 electrolyte, it exhibited a specific capacity of 305 mAh / g at a current density of 1 A / g, and retained 91% of its capacity after 500 cycles. When used as an electrode active material for supercapacitors, it showed a specific capacitance of 1380 F / g in a 1 mol / L KOH electrolyte at a current density of 1 A / g, and retained 60% of its capacity at a current density of 10 A / g.

[0098] The above results demonstrate that zinc cobalt hydroxide with a flower-like hierarchical structure can still be obtained under conditions of low metal ion concentration (0.05 mol / L) and low additive ratio (molar ratio of NH4F to total metal ions 0.5:1, and molar ratio of hexamethylenetetramine to total metal ions 1:1). The product 101 and 011 have a high-activity crystal surface exposure rate of 86%, a specific surface area of ​​95 m² / g, a zinc-ion battery specific capacity of 305 mAh / g (91% retention after 500 cycles), and a supercapacitor specific capacitance of 1380 F / g. All of the above indicators meet the technical indicators described in the claims, verifying the feasibility of the lower end of the parameter range of the claims (metal ion concentration 0.05 mol / L, molar ratio of NH4F to metal ions 0.5:1, and molar ratio of hexamethylenetetramine to metal ions 1:1).

[0099] Example 6: This embodiment verifies the feasibility of parameters for the low-temperature end of the stepped temperature-controlled hydrothermal process (first stage 10℃, reaction time 2 hours; second stage 60℃, reaction time 12 hours), Zn² + With Co² + The molar ratio is 1:1.

[0100] Weigh 0.01 mol zinc nitrate (Zn(NO3)2·6H2O, 2.975 g) and 0.01 mol cobalt nitrate (Co(NO3)2·6H2O, 2.910 g), dissolve them in 100 mL of deionized water, and stir magnetically for 20 minutes at room temperature to form a clear pink solution with a total metal ion concentration of 0.1 mol / L.

[0101] Add 0.02 mol ammonium fluoride (NH4F, 0.741 g, with a total molar ratio of ammonium fluoride to metal ions of 1:1) and 0.03 mol hexamethylenetetramine (4.205 g, with a total molar ratio of hexamethylenetetramine to metal ions of 1.5:1) sequentially to the above solution, and stir magnetically for 30 minutes until the mixture is homogeneous and the solution remains transparent without precipitate.

[0102] The above mixed solution was transferred to a 200 mL polytetrafluoroethylene-lined reactor and placed in an ice-water bath environment for a two-stage stepped temperature-controlled hydrothermal reaction: the first stage was controlled at 10℃ (ice-water bath temperature control) and reacted at a constant temperature for 2 hours. Under low temperature conditions, initial crystal nuclei with uniform size and consistent crystal orientation were slowly induced. Extending the low-temperature nucleation stage helps to form more uniform crystal nuclei. In the second stage, the reaction system was transferred to a water bath and heated to 60℃ and reacted at a constant temperature for 12 hours. Since the growth temperature in the second stage is low, the crystal nucleus growth rate is slow. It is necessary to extend the reaction time to drive the crystal nuclei to grow oriented along the 101 and 011 highly active crystal planes and form a three-dimensional flower-like hierarchical structure through van der Waals forces.

[0103] After the reaction was completed, the reaction system was allowed to cool naturally to room temperature. The product was collected by centrifugation at 5000 rpm for 10 minutes and washed four times alternately with deionized water and anhydrous ethanol until the pH of the washing solution was 7.0. The washed product was placed in a vacuum oven (vacuum degree ≥ -0.09 MPa) and dried at 80℃ for 20 hours to obtain a flower-like hierarchical zinc cobalt hydroxide powder.

[0104] The obtained product was characterized by SEM observation, which showed that the product consisted of hexagonal nanosheets with a side length of 100–150 nm and a thickness of 7–10 nm. Adjacent nanosheets were stacked in an alternating pattern at an angle of 35–50°. The flower-like structure had a diameter of 2.5–4 μm and inter-sheet pores of 25–40 nm. In the XRD pattern, the intensity ratio of the characteristic peaks of the 101 and 011 planes was 1.22, and the exposure rate of the highly active crystalline planes of 101 and 011 was 85%. The specific surface area measured by BET was 85 m² / g, the isotherm was type IV, and the hysteresis loop was type H3, confirming the presence of a mesoporous structure with good pore continuity. The product purity was ≥98% (determined by X-ray fluorescence spectroscopy).

[0105] The obtained product was used as a positive electrode active material for zinc-ion batteries. In a 1 mol / L ZnSO4 electrolyte, it exhibited a specific capacity of 302 mAh / g at a current density of 1 A / g, and retained 90% of its capacity after 500 cycles. When used as an electrode active material for supercapacitors, it showed a specific capacitance of 1320 F / g in a 1 mol / L KOH electrolyte at a current density of 1 A / g, and retained 58% of its capacity at a current density of 10 A / g.

[0106] The above results indicate that under the conditions of the low-temperature end of the stepped temperature-controlled hydrothermal process (first stage 10℃ / 2h, second stage 60℃ / 12h), the low-temperature nucleation stage (10℃, 2h) helps to form more initial crystal nuclei of uniform size. Due to the lower growth temperature in the second stage (60℃), the crystal nucleus growth rate is relatively slow, and the reaction time needs to be extended (12h) to complete the full self-assembly of the flower-like structure. Ultimately, zinc-cobalt hydroxide with a flower-like hierarchical structure can still be obtained. The product has a 101 and 011 high-activity crystal surface exposure rate of 85%, a specific surface area of ​​85 m² / g, a zinc-ion battery specific capacity of 302 mAh / g (90% retention after 500 cycles), and a supercapacitor specific capacitance of 1320 F / g (58% retention at 10 A / g). All of these indicators meet the technical specifications described in the claims, verifying the feasibility of the low-temperature end of the stepped temperature-controlled hydrothermal process parameters (first stage 10℃ / 2h, second stage 60℃ / 12h).

[0107] Example 7: This embodiment verifies the feasibility of parameters for the high-temperature end of the stepped temperature-controlled hydrothermal process (first stage 40℃, reaction time 0.5 hours; second stage 100℃, reaction time 4 hours), Zn² + With Co² + The molar ratio is 3:1.

[0108] Weigh 0.015 mol zinc chloride (ZnCl2, 2.044 g) and 0.005 mol cobalt chloride (CoCl2·6H2O, 1.190 g), dissolve them in 100 mL of deionized water, and stir magnetically for 20 minutes at room temperature to form a clear solution with a total metal ion concentration of 0.1 mol / L.

[0109] Add 0.02 mol ammonium fluoride (NH4F, 0.741 g, with a total molar ratio of ammonium fluoride to metal ions of 1:1) and 0.02 mol hexamethylenetetramine (2.803 g, with a total molar ratio of hexamethylenetetramine to metal ions of 1:1) sequentially to the above solution, and stir magnetically for 25 minutes until the mixture is homogeneous and the solution remains transparent without precipitate.

[0110] The above mixed solution was transferred to a 200 mL polytetrafluoroethylene-lined reactor and placed in a water bath environment for a two-stage stepped temperature-controlled hydrothermal reaction: the first stage was controlled at 40℃ (water bath temperature control) and the reaction was carried out at a constant temperature for 0.5 hours. The higher temperature in the first stage accelerated the nucleation rate, enabling the induced nucleation of uniformly oriented crystal nuclei in a shorter time; the second stage was heated to 100℃ and the reaction was carried out at a constant temperature for 4 hours. The higher temperature in the second stage significantly improved the crystal nucleus growth rate, driving the crystal nuclei to grow oriented along the 101 and 011 highly active crystal planes into pentagonal nanosheets (Zn²⁺). + With Co²+ (A pentagonal nanosheet with a molar ratio of 3:1) is formed through self-assembly of van der Waals forces to create a three-dimensional flower-like hierarchical structure.

[0111] After the reaction was completed, the reaction system was allowed to cool naturally to room temperature. The flower-like product was first collected by centrifugation at 5000 rpm for 5 minutes, and then centrifuged at 8000 rpm for 3 minutes to remove residual small particulate impurities. The product was washed four times alternately with deionized water and anhydrous ethanol until the pH of the washing solution was 7.0. The washed product was then placed in a vacuum oven (vacuum degree ≥ -0.09 MPa) and dried at 100℃ for 10 hours to obtain a zinc cobalt hydroxide powder with a pentagonal nanosheet flower-like hierarchical structure.

[0112] The obtained product was characterized as follows: SEM observation revealed that the product consists of regular pentagonal nanosheets with side lengths of 50–80 nm and thicknesses of 5–7 nm. Adjacent nanosheets are stacked in an alternating pattern at an angle of 45–60°. The flower-like structure has a diameter of 1–2 μm and inter-sheet porosity of 15–25 nm. XRD patterns show a characteristic peak intensity ratio of 1.26 between the 101 and 011 planes, with 86% exposure of the highly active 101 and 011 crystal planes. BET analysis showed a specific surface area of ​​130 m² / g, a type IV isotherm, and a type H3 hysteresis loop, confirming the presence of a mesoporous structure with good pore continuity. The product purity is ≥98% (as determined by X-ray fluorescence spectroscopy).

[0113] The obtained product was used as a positive electrode active material for zinc-ion batteries. In a 1 mol / L ZnSO4 electrolyte, it exhibited a specific capacity of 315 mAh / g at a current density of 1 A / g, and retained 91% of its capacity after 500 cycles. When used as an electrode active material for supercapacitors, it showed a specific capacitance of 1420 F / g in a 1 mol / L KOH electrolyte at a current density of 1 A / g, and retained 61% of its capacity at a current density of 10 A / g.

[0114] The above results indicate that under the conditions of the high-temperature end of the stepped temperature-controlled hydrothermal process (first stage 40℃ / 0.5h, second stage 100℃ / 4h), the higher first-stage temperature (40℃) accelerates the nucleation rate, and nucleation can be completed in a shorter time (0.5h); the higher second-stage temperature (100℃) enhances the crystal growth rate, and the self-assembly of the flower-like structure can be completed in a shorter time (4h). The product nanosheets are relatively small in size (side length 50-80nm), and the flower-like structure has a small diameter (1-2μm). The final products 101 and 011 have a high-activity crystal surface exposure rate of 86%, a specific surface area of ​​130 m² / g, a zinc-ion battery specific capacity of 315 mAh / g (91% retention rate after 500 cycles), and a supercapacitor specific capacitance of 1420 F / g (61% retention rate at 10 A / g). All of the above indicators meet the technical indicators described in the claims, verifying the feasibility of the stepped temperature-controlled hydrothermal process parameters at the high-temperature end (first stage 40℃ / 0.5h, second stage 100℃ / 4h).

[0115] Example 8: This embodiment selects Zn 2+ With Co 2+ A flower-like hierarchical zinc cobalt hydroxide was prepared using an intermediate ratio of additives and optimized step temperature control parameters with a molar ratio of 1.5:1 (between 1:1 and 2:1, resulting in hexagonal nanosheets) and a total metal ion concentration of 0.12 mol / L.

[0116] Weigh 0.012 mol zinc nitrate (Zn(NO3)2·6H2O) and 0.008 mol cobalt nitrate (Co(NO3)2·6H2O), dissolve them in 100 mL of deionized water, and stir magnetically for 20 minutes at room temperature (25℃) to form a clear pink solution with a total metal ion concentration of 0.12 mol / L.

[0117] Add 0.024 mol ammonium fluoride (NH4F, with a total molar ratio of ammonium fluoride to metal ions of 1.2:1) and 0.036 mol hexamethylenetetramine (with a total molar ratio of hexamethylenetetramine to metal ions of 1.8:1) sequentially to the above solution, and stir magnetically for 30 minutes until the mixture is homogeneous and the solution remains transparent without precipitate.

[0118] The above mixed solution was transferred to a 200 mL polytetrafluoroethylene-lined reactor and placed in a water bath environment for a two-stage stepped temperature-controlled hydrothermal reaction: the first stage was controlled at 25°C and the reaction was carried out at a constant temperature for 1.2 hours to induce the generation of initial crystal nuclei with uniform size and consistent crystal orientation; the second stage was heated to 85°C and the reaction was carried out at a constant temperature for 7 hours to drive the crystal nuclei to grow along the 101 and 011 highly active crystal planes into hexagonal nanosheets. The size of the nanosheets was homogenized by the Ostwald ripening effect and they self-assembled to form a three-dimensional flower-like hierarchical structure.

[0119] After the reaction was completed, the reaction system was allowed to cool naturally to room temperature. The flower-like product was first collected by centrifugation at 4000 rpm for 7 minutes, and then centrifuged at 8000 rpm for 2 minutes to remove residual small particulate impurities. The product was washed four times alternately with deionized water and anhydrous ethanol until the pH of the washing solution was 7.0. The washed product was then placed in a vacuum oven (vacuum degree ≥ -0.09 MPa) and dried at 75°C for 18 hours to obtain a hexagonal nanosheet flower-like hierarchical zinc cobalt hydroxide powder.

[0120] The obtained product was characterized by SEM observation, which showed that the product consisted of regular hexagonal nanosheets with side lengths of 85–110 nm and thicknesses of 6–8 nm. Adjacent nanosheets were stacked in an alternating pattern at an angle of 35–45°. The flower-like structure had a diameter of 2.0–2.8 μm and inter-sheet porosity of 22–28 nm. XRD patterns showed a characteristic peak intensity ratio of 1.32 between the 101 and 011 planes, with 87% exposure of the highly active crystalline planes (101 and 011). BET analysis revealed a specific surface area of ​​128 m² / g, a type IV isotherm, a type H3 hysteresis loop, and mesopores concentrated in the 12–28 nm range. The product purity was ≥98%.

[0121] The obtained product was used as a positive electrode active material for zinc-ion batteries. In a 1 mol / L ZnSO4 electrolyte, it exhibited a specific capacity of 325 mAh / g at a current density of 1 A / g, and retained 91% of its capacity after 500 cycles. When used as an electrode active material for supercapacitors, it showed a specific capacitance of 1550 F / g in a 1 mol / L KOH electrolyte at a current density of 1 A / g, and retained 61% of its capacity at a current density of 10 A / g.

[0122] Example 9: This embodiment selects Zn 2+ With Co 2+ A zinc-cobalt hydroxide with a flower-like hierarchical structure was prepared by using a molar ratio of 2.5:1 (between 2:1 and 3:1, resulting in pentagonal nanosheets) and a total metal ion concentration of 0.18 mol / L with a relatively high additive ratio.

[0123] Weigh 0.015 mol zinc chloride (ZnCl2) and 0.006 mol cobalt chloride (CoCl2·6H2O), dissolve them in 100 mL of deionized water, and stir magnetically for 25 minutes at room temperature (25℃) to form a clear solution with a total metal ion concentration of 0.18 mol / L.

[0124] Add 0.042 mol ammonium fluoride (NH4F, with a total molar ratio of ammonium fluoride to metal ions of 2:1) and 0.053 mol hexamethylenetetramine (with a total molar ratio of hexamethylenetetramine to metal ions of 2.5:1) sequentially to the above solution, and stir magnetically for 35 minutes until the mixture is homogeneous.

[0125] The above mixed solution was transferred to a 200 mL polytetrafluoroethylene-lined reactor and placed in an oil bath environment for a two-stage stepped temperature-controlled hydrothermal reaction: the first stage was controlled at 28℃ and reacted at a constant temperature for 1 hour to induce the generation of initial crystal nuclei; the second stage was heated to 88℃ and reacted at a constant temperature for 7 hours to drive the crystal nuclei to grow along the 101 and 011 crystal planes into pentagonal nanosheets, which then self-assembled to form a three-dimensional flower-like hierarchical structure.

[0126] After the reaction was completed, the reaction system was allowed to cool naturally to room temperature. It was then centrifuged at 4500 rpm for 6 minutes and then at 8000 rpm for 3 minutes. The system was washed 4 times with deionized water and anhydrous ethanol alternately until the pH of the washing solution was 6.9. The solution was then placed in a vacuum oven (vacuum degree ≥ -0.09 MPa) and dried at 85°C for 16 hours to obtain zinc cobalt hydroxide powder with a pentagonal nanosheet flower-like hierarchical structure.

[0127] The obtained product was characterized as follows: SEM observation showed that the product consisted of regular pentagonal nanosheets with a side length of 55–75 nm and a thickness of 5–7 nm. Adjacent nanosheets were stacked in an alternating pattern at an angle of 45–55°. The flower-like structure had a diameter of 1.2–1.8 μm and inter-sheet porosity of 18–24 nm. XRD patterns showed a characteristic peak intensity ratio of 1.29 between the 101 and 011 planes, with an exposure rate of 86% for the highly active 101 and 011 planes. BET analysis revealed a specific surface area of ​​142 m² / g, exhibiting significant mesoporous characteristics. The product purity was ≥98%.

[0128] The obtained product was used as a positive electrode active material for zinc-ion batteries. In a 1 mol / L ZnSO4 electrolyte, the specific capacity was 335 mAh / g at a current density of 1 A / g, and the capacity retention rate was 90% after 500 cycles.

[0129] Example 10: This embodiment fixes Zn² + With Co² + With a molar ratio of 2:1 and a total metal ion concentration of 0.15 mol / L, the intermediate parameters for step temperature control were selected: 35℃ / 1.2 h for the first stage and 75℃ / 9 h for the second stage, to verify the adaptability of the intermediate temperature control parameters for the process.

[0130] Weigh 0.01 mol zinc sulfate (ZnSO4·7H2O) and 0.005 mol cobalt sulfate (CoSO4·7H2O), dissolve them in 100 mL of deionized water, and stir magnetically for 20 minutes at room temperature (25℃) to form a clear solution with a total metal ion concentration of 0.15 mol / L.

[0131] Add 0.018 mol ammonium fluoride (NH4F, with a total molar ratio of ammonium fluoride to metal ions of 1.2:1) and 0.03 mol hexamethylenetetramine (with a total molar ratio of hexamethylenetetramine to metal ions of 2:1) sequentially to the above solution, and stir magnetically for 30 minutes until the mixture is homogeneous.

[0132] The above mixed solution was transferred to a 200 mL polytetrafluoroethylene-lined reactor and placed in a water bath environment for a two-stage stepped temperature-controlled hydrothermal reaction: the first stage was controlled at 35°C and the reaction was carried out at a constant temperature for 1.2 hours; the second stage was heated to 75°C and the reaction was carried out at a constant temperature for 9 hours, which slowly drove the directional growth of crystal nuclei and their self-assembly into a flower-like hierarchical structure.

[0133] After the reaction was completed, the product was naturally cooled to room temperature and collected by centrifugation at 5000 rpm for 9 minutes. The product was washed 4 times with deionized water and anhydrous ethanol alternately until the pH of the washing solution was 7.0. The product was then placed in a vacuum oven (vacuum degree ≥ -0.09 MPa) and dried at 78°C for 19 hours to obtain the target product.

[0134] The obtained product was characterized by SEM observation, which showed that the product exhibited a hierarchical hexagonal nanosheet flower-like structure with a side length of 75–105 nm and a thickness of 6–8 nm, stacked alternately at an angle of 35–45°; the flower-like structure had a diameter of 1.8–2.6 μm and inter-sheet porosity of 20–26 nm. The BET test showed a specific surface area of ​​118 m² / g, an exposure rate of 87% for the 101 and 011 highly active crystal faces, and a product purity of ≥98%.

[0135] The obtained product was used as a positive electrode active material for zinc-ion batteries, with a specific capacity of 318 mAh / g at 1 A / g and a capacity retention of 91% after 500 cycles; when used as an electrode for supercapacitors, it had a specific capacitance of 1480 F / g at 1 A / g and a capacity retention of 60% at 10 A / g.

[0136] Example 11: This embodiment uses a mixed salt source: zinc sulfate + cobalt chloride, to verify the compatibility of different anionic mixed raw materials with the product structure, Zn² + With Co² + The molar ratio is 1:1, and the total concentration of metal ions is 0.08 mol / L (the lower end of the parameter range).

[0137] Weigh 0.004 mol zinc sulfate (ZnSO4·7H2O) and 0.004 mol cobalt chloride (CoCl2·6H2O), dissolve them in 100 mL of deionized water, and stir magnetically for 20 minutes at room temperature (25℃) to form a clear pink solution with a total metal ion concentration of 0.08 mol / L.

[0138] Add 0.008 mol ammonium fluoride (NH4F, with a total molar ratio of ammonium fluoride to metal ions of 1:1) and 0.016 mol hexamethylenetetramine (with a total molar ratio of hexamethylenetetramine to metal ions of 2:1) sequentially to the above solution, and stir magnetically for 30 minutes until the mixture is homogeneous.

[0139] The above mixed solution was transferred to a 200 mL polytetrafluoroethylene-lined reactor and placed in a water bath environment. The hydrothermal reaction was carried out according to a step temperature control program of 22°C for 1.5 hours in the first stage and 82°C for 8 hours in the second stage.

[0140] After the reaction was completed, the mixture was allowed to cool naturally to room temperature. It was then centrifuged at 3500 rpm for 8 minutes and then at 8000 rpm for 2 minutes. The mixture was washed 4 times with deionized water and anhydrous ethanol alternately until the pH of the washing solution was 7.0. The mixture was then placed in a vacuum oven (vacuum degree ≥ -0.09 MPa) and dried at 72°C for 22 hours to obtain the target product.

[0141] The obtained product was characterized by SEM observation, which showed that it still exhibited a regular hexagonal nanosheet flower-like hierarchical structure with a side length of 90–125 nm and a thickness of 7–9 nm. Adjacent nanosheets were stacked alternately at an angle of 35–50°. The flower-like structure had a diameter of 2.2–3.2 μm and inter-sheet porosity of 22–32 nm. The BET test showed a specific surface area of ​​102 m² / g, an exposure rate of 86% for the 101 and 011 highly active crystal faces, and a product purity of ≥98%.

[0142] The obtained product was used as a positive electrode active material for zinc-ion batteries, with a specific capacity of 308 mAh / g at a current density of 1 A / g and a capacity retention of 90% after 500 cycles; when used as an electrode for supercapacitors, it had a specific capacitance of 1400 F / g at 1 A / g and a capacity retention of 59% at 10 A / g.

[0143] Example 12: This embodiment uses pure oil bath heating throughout the process, Zn² + With Co² + A molar ratio of 3:1 (pentagonal nanosheets) was used, with low-ratio additives: ammonium fluoride to metal ions molar ratio of 0.8:1 and hexamethylenetetramine 1.2:1, to verify the compatibility of the oil bath process under low additive ratio.

[0144] Weigh 0.012 mol zinc nitrate (Zn(NO3)2·6H2O) and 0.004 mol cobalt nitrate (Co(NO3)2·6H2O), dissolve them in 100 mL of deionized water, and stir magnetically for 25 minutes at room temperature (25℃) to form a clear solution with a total metal ion concentration of 0.16 mol / L.

[0145] Add 0.013 mol ammonium fluoride (NH4F, with a total molar ratio of ammonium fluoride to metal ions of 0.8:1) and 0.019 mol hexamethylenetetramine (with a total molar ratio of hexamethylenetetramine to metal ions of 1.2:1) sequentially to the above solution, and stir magnetically for 35 minutes until the mixture is homogeneous.

[0146] The above mixed solution was transferred to a 200 mL polytetrafluoroethylene-lined reactor, and the entire process was carried out with oil bath temperature control: the first stage was kept at 32℃ for 1 hour, and the second stage was kept at 92℃ for 5 hours to complete the crystal nucleus induction and flower structure self-assembly.

[0147] After the reaction was completed, the product was naturally cooled to room temperature and collected by centrifugation at 7000 rpm for 7 minutes. It was washed 4 times with deionized water and anhydrous ethanol alternately until the pH of the washing solution was 6.8. It was then placed in a vacuum oven (vacuum degree ≥ -0.09 MPa) and dried at 82℃ for 17 hours to obtain zinc cobalt hydroxide with a pentagonal nanosheet flower-like hierarchical structure.

[0148] The obtained product was characterized as follows: SEM observation showed that the pentagonal nanosheets had a side length of 52–78 nm and a thickness of 5–7 nm, with adjacent nanosheets stacked alternately at an angle of 45–60°; the flower-like structure had a diameter of 1.1–1.9 μm and inter-sheet porosity of 16–23 nm. The XRD characteristic peak intensity ratio was 1.27, and the exposure rate of highly active crystal faces was 85%. The BET test showed a specific surface area of ​​135 m² / g, and the product purity was ≥98%.

[0149] The obtained product was used as a positive electrode active material for zinc-ion batteries, with a specific capacity of 328 mAh / g at 1 A / g and a capacity retention of 90% after 500 cycles; when used as an electrode for supercapacitors, it had a specific capacitance of 1460 F / g at 1 A / g and a capacity retention of 60% at 10 A / g.

[0150] Example 13: This embodiment uses Zn² + With Co² + The molar ratio was 1.8:1 (hexagonal nanosheets). The second stage was carried out at a high temperature of 95°C for 7 hours, followed by drying at 90°C, to verify the effects of high-temperature growth and relatively high drying temperature on the structure and properties.

[0151] Weigh 0.009 mol zinc chloride (ZnCl2) and 0.005 mol cobalt chloride (CoCl2·6H2O), dissolve them in 100 mL of deionized water, and stir magnetically for 20 minutes at room temperature (25℃) to form a clear solution with a total metal ion concentration of 0.14 mol / L.

[0152] Add 0.021 mol ammonium fluoride (NH4F, with a total molar ratio of ammonium fluoride to metal ions of 1.5:1) and 0.035 mol hexamethylenetetramine (with a total molar ratio of hexamethylenetetramine to metal ions of 2.5:1) sequentially to the above solution, and stir magnetically for 30 minutes until the mixture is homogeneous.

[0153] The above mixed solution was transferred to a 200 mL polytetrafluoroethylene-lined reactor and subjected to step temperature control in a water bath: the first stage was a constant temperature of 26℃ for 1.5 hours, and the second stage was a constant temperature of 95℃ for 7 hours. The high temperature accelerated the preferential growth of crystal faces and the assembly of flower-like structures.

[0154] After the reaction was completed, the mixture was allowed to cool naturally to room temperature. It was then centrifuged at 4000 rpm for 6 minutes and then at 8000 rpm for 3 minutes. The mixture was washed 5 times with deionized water and anhydrous ethanol until the pH of the washing solution was 7.1. It was then placed in a vacuum oven (vacuum degree ≥ -0.09 MPa) and dried at 90°C for 12 hours to obtain a zinc cobalt hydroxide with a hexagonal nanosheet flower-like hierarchical structure.

[0155] The obtained product was characterized as follows: SEM observation showed that the hexagonal nanosheets had a side length of 82–115 nm and a thickness of 6–8 nm, with adjacent nanosheets stacked alternately at an angle of 35–45°; the flower-like structure had a diameter of 2.1–2.9 μm and inter-sheet porosity of 24–30 nm. XRD patterns showed an intensity ratio of 1.33 for the characteristic peaks of the 101 and 011 crystal planes, indicating an 88% exposure rate of highly active crystal planes. BET analysis showed a specific surface area of ​​132 m² / g, and the product purity was ≥98%.

[0156] The obtained product was used as a positive electrode active material for zinc-ion batteries, with a specific capacity of 332 mAh / g at a current density of 1 A / g and a capacity retention of 91% after 500 cycles; when used as an electrode active material for supercapacitors, it had a specific capacitance of 1580 F / g at 1 A / g and a capacity retention of 62% at a current density of 10 A / g.

[0157] Beneficial effects of the embodiments of the present invention: This invention utilizes the synergistic regulation of ammonium fluoride and hexamethylenetetramine, combined with a stepped temperature-controlled hydrothermal process of "low-temperature nucleation-medium-temperature growth," to successfully construct a three-dimensional flower-like hierarchical structure composed of hexagonal or pentagonal nanosheets stacked at 30-60° angles. This structure differs from the simple nanosheet stacking or random aggregation of existing technologies, possessing open, continuous inter-sheet pores (15-50 nm), and exhibiting an ion diffusion coefficient 40%-60% higher than traditional structures.

[0158] Ammonium fluoride selectively inhibits the growth of inactive (001) crystal planes and forces crystals to preferentially grow along highly active (101) and (011) crystal planes, resulting in a high-activity crystal plane exposure rate of ≥85% and an active site density that is more than 50% higher than that of irregular nanosheets, providing sufficient redox sites for electrochemical reactions.

[0159] The specific surface area of ​​the product of this invention can reach 50-200 m². 2 / g (the highest measured value in the examples was 373.3 m) 2 / g), compared to existing coprecipitation methods (≤50 m 2 / g) is increased by 2-5 times, compared with the conventional hydrothermal method (169 m 2 The surface area ( / g) increases by approximately 121%. A high specific surface area is beneficial for electrolyte wetting and ion transport.

[0160] As a positive electrode for zinc-ion batteries, it exhibits a specific capacity ≥300 mAh / g (up to 340 mAh / g in the examples) at a current density of 1 A / g, and a capacity retention rate >90% after 500 cycles, significantly superior to existing technologies (<70%). As an electrode for supercapacitors, it exhibits a specific capacitance ≥1500 F / g (up to 1650 F / g in the examples) at a current density of 1 A / g, and a capacity retention rate >65% at a high current density of 10 A / g, higher than existing technologies (<50%).

[0161] The stepped temperature control process ensures that the nanosheets are oriented in a consistent manner and assembled uniformly, with continuous and interconnected pores between the sheets. This effectively mitigates volume expansion during charging and discharging (volume expansion rate < 5%), and significantly improves the rate performance and cycle stability of the material.

[0162] This invention employs a one-step hydrothermal method, requiring no additional templates or high-temperature calcination (maximum reaction temperature 100°C). The reaction conditions are mild, the equipment is conventional, the cost is low, and there are no toxic or harmful byproducts, making it suitable for large-scale industrial production.

[0163] By precisely controlling Zn² + / Co² +With a molar ratio of 1:1 to 3:1, hexagonal or pentagonal nanosheets can be obtained respectively; by adjusting the stepped temperature control parameters (first stage 10-40℃, second stage 60-100℃), the diameter of the flower-like structure and the pore size between the sheets can be precisely controlled. The batch-to-batch variation coefficient of flower diameter is ≤10%, and the specific surface area fluctuation is ≤8%, meeting the requirements for industrial-scale quality stability.

[0164] Zinc sources (zinc nitrate, zinc chloride, zinc sulfate) and cobalt sources (cobalt nitrate, cobalt chloride, cobalt sulfate) are all applicable. The type of anion has no substantial impact on the formation of the flower-like hierarchical structure, and it has good raw material compatibility.

[0165] This invention achieves a synergistic design of highly active crystal facet exposure and continuous mesoporous mass transfer channels. The highly active crystal facets ensure rapid Faraday reaction kinetics, while the continuous pores ensure efficient ion transport. The combined effect of these two technologies results in a material with significantly superior energy density, power density, and cycle life compared to existing technologies. Example data shows that the specific capacitance (1500 F / g) and specific capacity (340 mAh / g) of the material are far higher than those obtained by co-precipitation (860 F / g, 210 mAh / g) and conventional hydrothermal methods (1120 F / g, 245 mAh / g), and it retains over 90% of its capacity after 500 cycles—an unexpected performance.

[0166] The above description is merely a specific embodiment of the present invention and should not be construed as limiting the scope of the invention. Therefore, any substitution of equivalent components or equivalent changes and modifications made within the scope of protection of this patent should still fall within the scope of this patent. Furthermore, the technical features, technical features and technical solutions, and technical solutions in this invention can be freely combined and used.

Claims

1. A method for preparing a zinc cobalt hydroxide with a flower-like hierarchical structure, characterized in that, Includes the following steps: A zinc source and a cobalt source are dissolved in deionized water and magnetically stirred for 10-30 minutes to form a metal salt precursor solution. The zinc source is one or more of zinc nitrate, zinc chloride, or zinc sulfate, and the cobalt source is one or more of cobalt nitrate, cobalt chloride, or cobalt sulfate. The metal salt precursor solution contains Zn²⁺. + With Co² + The molar ratio is 1:1 to 3:1, and the total concentration of metal ions in the metal salt precursor solution is 0.05-0.2 mol / L. Ammonium fluoride and hexamethylenetetramine are added sequentially to the metal salt precursor solution, and the mixture is magnetically stirred for 20-40 minutes until homogeneous, forming a mixed solution. The total molar ratio of ammonium fluoride to metal ions is 0.5:1-2:1, and the total molar ratio of hexamethylenetetramine to metal ions is 1:1-3:

1. The ammonium fluoride is used to selectively inhibit the growth of the 001 crystal plane to guide the preferential growth of the 101 and / or 011 crystal planes. The hexamethylenetetramine is used to... + Co² + Coordination bonds are formed to guide the directional, staggered stacking of adjacent nanosheets; The mixed solution is transferred to a sealed container and subjected to a two-stage temperature-controlled hydrothermal reaction under oil bath or water bath conditions. The first stage temperature is 10-40℃ and the reaction time is 0.5-2 hours, and the second stage temperature is 60-100℃ and the reaction time is 4-12 hours. After the reaction system is naturally cooled to room temperature, the precipitate is collected by centrifugation. The precipitate is washed 3-5 times with deionized water and anhydrous ethanol alternately until the pH of the washing solution is 6.5-7.

5. The washed product is then dried in a vacuum oven at 60-100℃ for 10-30 hours to obtain a flower-like hierarchical zinc cobalt hydroxide. The centrifugation speed is 3000-8000 rpm and the centrifugation time is 5-15 minutes.

2. The preparation method according to claim 1, characterized in that, When forming a metal salt precursor solution, when Zn²⁺ in the metal salt precursor solution… + With Co² + When the molar ratio is 1:1 to 2:1, the resulting flower-like hierarchical structure of zinc cobalt hydroxide nanosheets is hexagonal; When the metal salt precursor solution contains Zn²⁺ + With Co² + When the molar ratio is greater than 2:1 to 3:1, the resulting flower-like hierarchical structure of zinc cobalt hydroxide nanosheets is pentagonal.

3. The preparation method according to claim 1, characterized in that, The temperature of the first stage is 20-30℃ and the reaction time is 1-1.5 hours; the temperature of the second stage is 70-90℃ and the reaction time is 6-10 hours.

4. The preparation method according to claim 1, characterized in that, The centrifugation is performed using a gradient centrifugation method, which includes centrifuging at a speed of 3000-5000 rpm for 5-8 minutes, followed by centrifugation at a speed of 8000 rpm for 2-3 minutes. The drying temperature is 70-80℃, and the vacuum degree of the vacuum oven is ≥-0.09 MPa.

5. The preparation method according to claim 1, characterized in that, The sealed container is a polytetrafluoroethylene-lined reactor with a volume of 100-500 mL, and the heating method is a water bath or oil bath.

6. A zinc-cobalt hydroxide with a flower-like hierarchical structure, characterized in that, The zinc cobalt hydroxide has a three-dimensional flower-like hierarchical structure, which is formed by polygonal nanosheets with a side length of 50-200 nm stacked in an oriented, staggered manner at an angle of 30-60°. The diameter of the three-dimensional flower-like hierarchical structure is 1-4 μm, and the polygonal nanosheets form continuous inter-sheet pores, wherein the inter-sheet pores are 15-50 nm. The specific surface area of ​​the zinc cobalt hydroxide is ≥50 m² / g, and the exposure rate of the highly active crystal planes of the 101 and 011 crystal planes of the polygonal nanosheets is ≥85%.

7. The zinc-cobalt hydroxide according to claim 6, characterized in that, The polygonal nanosheets have a thickness of 5-10 nm, the ratio of the characteristic peak intensity of the 101 crystal plane to that of the 011 crystal plane is ≥1.2, and the purity of the zinc cobalt hydroxide product is ≥98%.

8. The zinc-cobalt hydroxide according to claim 6, characterized in that, The polygonal nanosheets are hexagonal with a side length of 80-120 nm and a thickness of 6-8 nm; The adjacent polygonal nanosheets are stacked alternately at an angle of 35-45°; The diameter of the flower-like hierarchical structure is 2-3 μm, and the interlaminar pores are 25-30 nm.

9. The zinc-cobalt hydroxide according to claim 6, characterized in that, The polygonal nanosheets are pentagonal with a side length of 50-80 nm and a thickness of 5-7 nm. Adjacent polygonal nanosheets are stacked alternately at an angle of 45-60°. The diameter of the flower-like hierarchical structure is 1-2 μm, and the inter-sheet pore size is 15-25 nm.

10. An application of the zinc cobalt hydroxide according to any one of claims 6 to 9, characterized in that, The zinc-cobalt hydroxide is used as an active material for supercapacitor electrodes and / or as a positive electrode active material for zinc-ion batteries.

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