Application of NiMo-based oxysulfide solid core-shell structure with ammonium intercalation as electrode material for zinc ion hybrid supercapacitors

Abstract

The present invention discloses a solid core-shell structured ammonium intercalated nickel sulfide / nickel oxyhydroxide@molybdenum disulfide, the chemical formula of which is Ni3S2 / Ni3O2(OH)4@MoS2. The preparation method thereof is also disclosed, which adopts a simple two-step hydrothermal synthesis method. First, ammonium molybdate tetrahydrate is used as a molybdenum source to synthesize NH4 + The intercalated molybdenum glycerate sphere template is then hydrothermally vulcanized together with the nickel foam substrate, and the resulting sample is NH4 + Intercalated solid core-shell structured nickel sulfide / nickel oxyhydroxide@molybdenum disulfide. This material, when used as an electrode material for zinc ion hybrid supercapacitors, exhibits higher specific capacity and better cycling stability than materials synthesized using conventional molybdenum sphere templates.

Description

Technical Field

[0001] The present invention belongs to the field of new energy material technology and supercapacitors, and specifically relates to self-templated synthesis of transition metal oxysulfides and their application in supercapacitors. Background Art

[0002] Supercapacitors, as one of the new energy storage devices available, offer high safety, high power density, and environmental friendliness, making them a promising alternative to batteries. However, their low energy density limits their application in large-scale energy storage devices. The energy density of supercapacitors depends on the material's capacity and voltage range. Therefore, conventional approaches to increasing capacitor energy density involve developing high-performance battery-type cathode materials and constructing asymmetric supercapacitor devices to enhance their specific capacity and voltage range. Metal oxides / sulfur compounds / hydroxides are typical battery-type materials, offering advantages such as low cost, structural stability, and high specific capacity. MoS2 is a commonly used energy storage electrode material due to its large interlayer spacing and excellent conductivity. However, pure MoS2 is prone to accumulation during charge and discharge, resulting in a limited number of active sites, which compromises its electrochemical performance. Ni-based sulfur / oxides, while offering advantages such as high specific capacity and good conductivity, often exhibit poor cycling stability in supercapacitors. Therefore, constructing Mo-Ni-based heterostructures through single- or multi-step reactions can leverage the complementary advantages of the components and enhance their energy storage performance through synergistic effects. Constructing a stable core-shell structure is also a key strategy for enhancing material stability.

[0003] Expanding the voltage range is the key to improving the energy density of materials. Limited by the low energy density and low voltage range of carbon-based negative electrode materials, the energy density of conventional asymmetric supercapacitor devices is still unsatisfactory. Zn plates have a lower voltage (-0.763V vs standard hydrogen electrode), a higher theoretical specific capacity, good stability, and a low price. Using them as negative electrodes to construct zinc ion hybrid capacitors can effectively increase the voltage range of the device, thereby increasing the energy density, and is a current research hotspot. However, the interlayer spacing of conventional supercapacitor materials is small, which is not conducive to the storage of zinc ions with a larger hydrated ion radius. Therefore, how to improve the zinc storage performance of the material is the key to current research.

[0004] In view of the above reasons, the present invention is proposed Summary of the Invention

[0005] In view of the above problems, the present invention provides an ammonium radical NH4 +This invention relates to an intercalated solid core-shell electrode material, its preparation method, and its application. The invention utilizes a self-templating method assisted by hydrothermal vulcanization to in-situ grow a NiMo-based oxysulfide electrode material on nickel foam. This electrode material is used to assemble high-performance zinc ion hybrid supercapacitors, exhibiting high specific capacity and stability.

[0006] One of the purposes of the present invention is to provide a solid core-shell structure supercapacitor electrode material NH4 + The intercalated nickel sulfide / nickel oxyhydroxide@molybdenum disulfide has the chemical formula Ni3S2 / Ni3O2(OH)4@MoS2.

[0007] The second object of the present invention is to provide NH4 + A method for preparing an intercalated Ni3S2 / Ni3O2(OH)4@MoS2 electrode material, the method comprising the following steps:

[0008] 1. Solvothermal synthesis of NH4 + Intercalated molybdenum glycerate spheres (N-MoG)

[0009] (1) Prepare an aqueous solution of ammonium molybdate tetrahydrate, slowly add it dropwise to a mixed solution of glycerol and isopropyl alcohol, and mix uniformly by ultrasonication.

[0010] (2) The mixed solution of step (1) is transferred into a hydrothermal reactor, placed in an oven and heated for a period of time, and then naturally cooled. The product is centrifuged, washed, and dried for later use.

[0011] 2. Synthesis of NH4 by hydrothermal sulfidation + Intercalated Ni3S2 / Ni3O2(OH)4@MoS2(N-NiMo-OS)

[0012] (3) Dissolve an appropriate amount of N-MoG and thiourea synthesized above in a mixed solution of water and ethanol, and stir and ultrasonically mix them evenly.

[0013] (4) The mixed solution in step (3) and the treated nickel foam are transferred into a reaction kettle, placed in an oven for heating, and then naturally cooled. The product is washed and vacuum-dried for standby use.

[0014] The molar amount of ammonium molybdate tetrahydrate in step (1) is 1.5 mmol, the volume ratio of solvent water, glycerol and isopropanol is 3:2:7, the total volume is 36 mL, and the addition time is 10 min.

[0015] The heating temperature in step (2) is 190 ο C, holding time is 3h.

[0016] In step (3), the mass of the precursor is 8 mg, the molar amount of thiourea is 0.1-0.2 mmol, the volume ratio of water to ethanol is 8:1, and the total volume is 63 mL.

[0017] The size of the nickel foam in step (4) is 3cm*3cm.

[0018] The heating temperature in step (4) is 180 ο C, the holding time is 3h-9h. Preferably, the holding time is 6h.

[0019] The third object of the present invention is to provide a solid core-shell structure of ammonium intercalated nickel sulfide / nickel oxyhydroxide@

[0020] MoS2 is used as an electrode for zinc ion hybrid supercapacitors, with a specific capacity of 327.5 mAh g at a current density of 1 A / g. -1 ; When the power density is 1710W / kg, the energy density reaches 610.6Wh / kg.

[0021] Compared with the prior art, the present invention has the following main advantages and beneficial effects:

[0022] (1) The present invention prepares NH4 + The intercalated MoG template has a larger volume and interlayer spacing, which enables the subsequent vulcanization reaction to proceed completely.

[0023] (2) Preparation of NH4 according to the present invention + Intercalated Ni3S2 / Ni3O2(OH)4@MoS2 core-shell structure The intercalated ions mainly exist in the MoS2 core structure, so the solid structure can provide fast ion diffusion channels.

[0024] (3) When the electrode material of the present invention is used in zinc ion hybrid supercapacitors, it has high specific capacity, good rate performance and excellent stability, high power density and energy density, and is a very promising electrode material. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be derived from these drawings without inventive effort.

[0026] Figure 1 This is a scanning electron microscope image of the N-MoG template sphere prepared in Example 1.

[0027] Figure 2This is the transmission electron microscope image of the core-shell structure Ni3S2 / Ni3O2(OH)4@MoS2 prepared in Example 1.

[0028] Figure 3 This is a scanning electron microscope image of MoG prepared in Comparative Example 1.

[0029] Figure 4 Infrared images of N-MoG and MoG template spheres prepared in Example 1 and Comparative Example 1.

[0030] Figure 5 This is the transmission electron microscope image of the core-shell structure Ni3S2 / Ni3O2(OH)4@MoS2 prepared in Comparative Example 1.

[0031] Figure 6 This is the scanning electron microscope image of the core-shell structure Ni3S2 / Ni3O2(OH)4@MoS2 prepared in Comparative Example 2.

[0032] Figure 7 This is the scanning electron microscope image of the core-shell structure Ni3S2 / Ni3O2(OH)4@MoS2 prepared in comparative example 3.

[0033] Figure 8 The constant current charge and discharge curves of Example 1 and Comparative Examples 1, 2, and 3 at the same current density are shown. DETAILED DESCRIPTION

[0034] To make the purpose, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention are described in detail below. Obviously, the embodiments described are only some of the embodiments of the present invention, rather than all of them. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0035] Example 1:

[0036] 1. Solvothermal synthesis of NH4 + Intercalated molybdenum glycerate spheres (N-MoG)

[0037] (1) Weigh 0.15 mmol of ammonium molybdate tetrahydrate and dissolve it in 9 mL of deionized water. Slowly add it dropwise to a mixed solution containing 6 mL of glycerol and 27 mL of isopropanol. Place it on a magnetic stirrer and stir and ultrasonicate to mix it evenly.

[0038] (2) The mixed solution of step (1) was transferred into a hydrothermal reactor, placed in an oven and heated to 190° C. and maintained for 3 h, then naturally cooled, and the product was centrifuged, washed, and dried for later use.

[0039] 2. NH4 +Synthesis of intercalated Ni3S2 / Ni3O2(OH)4@MoS2(N-NiMo-OS)

[0040] (3) 8 mg of the synthesized N-MoG and 0.1 mmol of thiourea were dissolved in 63 mL of a mixed solution of water and ethanol (volume ratio of 8:1), and stirred and ultrasonically mixed until uniform.

[0041] (4) The mixed solution in step (3) and the treated nickel foam (3 cm*3 cm) were transferred to a reactor, placed in an oven, heated to 180° C., and maintained for 6 h, then naturally cooled, the product was washed, and vacuum dried for later use.

[0042] The above-prepared solid core-shell structure of ammonium intercalated nickel sulfide / nickel oxyhydroxide@molybdenum disulfide was made into a supercapacitor electrode according to the following method:

[0043] (1) The dried nickel foam was cut into 1 cm × 2 cm rectangular pieces to serve as the positive electrode.

[0044] (2) Using Zn plate as the negative electrode, 6M potassium hydroxide and 0.2M zinc acetate solution as the electrolyte, button cells were assembled and electrochemically tested on a CHI760E electrochemical workstation and a blue light.

[0045] Comparative Example 1:

[0046] The experimental steps of this comparative example are basically the same as those in Example 1, except that the molybdenum source in step (1) is ammonium molybdate tetrahydrate, while the molybdenum source in this comparative example is molybdenum pentachloride. + The template and product were named MoG and NiMo-OS, respectively.

[0047] Comparative Example 2:

[0048] The experimental steps of this comparative example are basically the same as those of Example 1, except that the reaction time in step (4) is different. The reaction time in this comparative example is 3 hours.

[0049] Comparative Example 3:

[0050] The experimental steps of this comparative example are basically the same as those of Example 1, except that the reaction time in step (4) is different. The reaction time in this comparative example is 9 hours.

[0051] Comparative Example 4:

[0052] The specific synthesis process of this comparative example refers to the literature J.Mater.Chem.A, 2019, 7, 1187–1195.

[0053] Figure 1This is a scanning electron microscope image of the template N-MoG prepared in Example 1. It can be seen from the image that the diameter of the sphere is about 4 μm and the surface is smooth.

[0054] Figure 2 This is a transmission electron micrograph of N-NiMo-OS prepared in Example 1. The image shows a distinct core-shell structure, with a solid spherical core with a radius of 1.5 μm and an outer layer of approximately 5 μm in size. Compared to the MoG template, the significantly smaller core size indicates faster ion diffusion and more complete sulfurization.

[0055] Figure 3 This is a scanning electron microscope image of the MoG template prepared in Comparative Example 1. It can be seen from the image that the prepared template has a diameter of about 700 nm and a smooth surface. Its structure and dimensions are similar to those of Comparative Example 4.

[0056] Figure 4 The infrared images of the templates prepared in Example 1 and Comparative Example 1. It can be seen from the figure that the N-MoG template prepared in Example 1 has an infrared wavelength of 1406 cm -1 The peaks on the left and right are mainly due to the presence of ammonium ions. However, the template prepared in Comparative Example 1 does not have the corresponding peaks, which confirms the successful synthesis of the template with ammonium ion intercalation.

[0057] Figure 5 This is a transmission electron micrograph of NiMo-OS prepared in Comparative Example 1. The product shows a solid core-shell structure with a core radius of approximately 650 nm, surrounded by a layered structure. The core size does not change much compared to the template, indicating slow ion diffusion and incomplete sulfurization.

[0058] Figure 6 This is a scanning electron microscope image of NiMo-OS prepared in comparative example 2. From the image, it can be seen that the product has a core-shell structure with less outer layer structure coating.

[0059] Figure 7 This is a scanning electron microscope image of NiMo-OS prepared in comparative example 3. From the image, it can be seen that the product has a core-shell structure, and the outer layers have obvious accumulation, resulting in the separation of the core structure and the layered structure.

[0060] Figure 8 The constant current charge-discharge curves for Example 1 and Comparative Examples 1, 2, and 3 at the same current density are shown. Within the appropriate potential window (0-0.5 V), the charge-discharge curves at the same scan rate show that Example 1 achieves the highest capacitance and the best performance. This indicates that 6 h in Example 1 is the optimal curing time. Furthermore, the products with reaction times of 3-9 hours all exhibited higher capacities than the product obtained with the template replaced in Comparative Example 1, demonstrating the superiority of the N-MoG template.

[0061] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A solid core-shell structured ammonium intercalated nickel sulfide / nickel oxyhydroxide@molybdenum disulfide, characterized in that: The chemical formula is Ni3S2 / Ni3O2(OH)4@MoS2, and its shape is a nano-layered structure covering a solid spherical structure, with an ammonium intercalation core structure; The preparation method of the solid core-shell structured ammonium intercalated nickel sulfide / nickel oxyhydroxide@molybdenum disulfide is as follows: (1) preparing a molybdenum salt solution, adding it dropwise to a mixed solution of glycerol and isopropyl alcohol, and ultrasonicating to obtain a uniform mixed solution; wherein the molybdenum salt is ammonium molybdate or ammonium molybdate tetrahydrate; (2) The solution of step (1) is transferred into a hydrothermal reactor, placed in an oven for heating, and then naturally cooled to obtain a precursor precipitate, which is then centrifuged, washed, and dried for later use; (3) dissolving the precursor of step (2) and an appropriate amount of thiourea in a mixed solution of water and ethanol, stirring and ultrasonicating to obtain a uniform mixed solution; (4) The solution from step (3) and the treated nickel foam are transferred into a hydrothermal reactor, placed in an oven and heated at 180°C for 3-6 hours, and then cooled naturally to obtain a sample. The sample is rinsed, washed, and vacuum-dried for later use.

2. The method for preparing a solid core-shell structured ammonium intercalated nickel sulfide / nickel oxyhydroxide@molybdenum disulfide according to claim 1, characterized in that: The heating time in step (4) is 6 h.

3. A solid core-shell structured ammonium intercalated nickel sulfide / nickel oxyhydroxide@molybdenum disulfide as described in claim 1, which can be used as an electrode material in a zinc ion hybrid supercapacitor.

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