1,4-benzenedithiol-modified titanium dioxide / nickel hydroxide heterojunction catalyst for lithium-sulfur batteries

Abstract

This invention provides an application of a 1,4-phenylenediol-modified titanium dioxide / nickel hydroxide heterojunction catalyst as a membrane coating material in lithium-sulfur batteries, belonging to the field of lithium-sulfur battery technology. The catalyst is constructed using a transition metal oxide heterojunction TiO2 / Ni(OH)2 as a substrate, modified by in-situ growth of the sulfur-containing organic compound 1,4-phenylenediol on its surface. This design, through the synergistic effect of the TiO2 / Ni(OH)2 heterojunction and the organic sulfur compound, significantly enhances the physicochemical adsorption and catalytic conversion efficiency of lithium polysulfides, thereby effectively suppressing the shuttle effect and improving battery cycle stability and reaction kinetics. This invention not only provides an efficient solution to the polysulfide shuttle problem but also offers a feasible path for the commercial application of lithium-sulfur batteries under high sulfur loading and low electrolyte conditions, which is of great significance for promoting the development of high-energy-density energy storage systems.

Description

Technical Field

[0001] This invention relates to the field of lithium-sulfur batteries, and more particularly to a 1,4-benzenedithiol-modified titanium dioxide / nickel hydroxide heterojunction catalyst suitable for lithium-sulfur battery separator coating modification, its preparation method, and its application. Background Technology

[0002] Among numerous novel energy storage solutions, lithium-sulfur batteries exhibit unique advantages. Their technological advantages are not only reflected in the 1675 mAh g⁻¹ -1 The theoretical specific capacity of the sulfur cathode lies not only in its ability to construct a completely new energy storage paradigm, but also in its ability to achieve energy conversion through multi-electron transfer reactions, unlike the "intercalation-deintercalation" mechanism of lithium-ion batteries. This breakthrough in mechanism enables a theoretical energy density of 2600Wh / kg, equivalent to improving the performance of existing power batteries by 7 times. Sulfur, the fifth most abundant element in the Earth's crust, has a natural abundance 35 times that of lithium, and its mining and processing are environmentally friendly. Compared to heavy metal oxide cathodes that require complex smelting, sulfur-based materials have overwhelming advantages in cost and sustainability. The introduction of lithium metal anodes breaks the capacity limitations of traditional graphite anodes, achieving a capacity of 3860mAh / kg. -1 The theoretical specific capacity signifies a significant increase in energy storage per unit mass. Lithium-sulfur batteries, with their high theoretical energy density, abundant sulfur resources, low cost, and environmentally friendly characteristics, have become a key candidate for next-generation energy storage systems, driven by the rapid development of demand in low-altitude unmanned aerial vehicles and portable electronic devices.

[0003] However, the biggest problem affecting the electrochemical performance of lithium-sulfur batteries in practical applications is the shuttle effect of polysulfides. During charging and discharging, the meso-phase polysulfides generated at the sulfur cathode are easily soluble in the electrolyte. Driven by the concentration gradient, the dissolved polysulfides migrate towards the anode and react with metallic lithium to form short-chain sulfides. These short-chain sulfides then diffuse back to the cathode and are re-oxidized into long-chain polysulfides. This repeated process of dissolution, diffusion, reduction, and oxidation is called the "shuttle effect." This phenomenon not only causes irreversible loss of active materials and rapid capacity decay, but also leads to electrochemical polarization on the surface of the lithium anode, forming a high-resistance passivation layer, which significantly reduces lithium-ion transport efficiency and coulombic efficiency, ultimately causing the battery cycle performance to deteriorate.

[0004] Transition metal oxides (TMOs) possess strong polarity and can utilize Lewis acid-base interactions and oxygen vacancies to fix and catalyze polysulfides, thereby reducing the loss of active sulfur materials during lithium-sulfur battery operation. Studies have found that the conductivity and catalytic activity of single TMOs are relatively limited, resulting in poor redox kinetics for lithium polysulfides. The inherent poor conductivity of TMOs also needs to be addressed. In the construction of heterojunction structures, the spontaneous electric field within the heterojunction structure solves the problem of poor conductivity, and the increased number of active metal coordination centers expands the catalytically active sites in the material, significantly improving its redox reaction kinetics. For example, Chinese invention patent CN115621435A discloses a positive electrode host material for lithium-sulfur batteries based on a manganese sulfide-molybdenum disulfide heterojunction. This material exhibits strong chemisorption of polysulfides, effectively mitigating the shuttle effect and improving the kinetics of the electrode reaction process.

[0005] However, current catalysts used in research typically serve as host materials for sulfur cathodes, requiring reaction and recombination with molten sulfur. This process still faces challenges such as complex preparation processes, high energy consumption, and reduced volumetric energy density of sulfur cathodes. In particular, there is a lack of materials that can be prepared and applied using simple, low-energy methods, possessing both strong chemical anchoring capabilities and highly efficient electrocatalytic activity. This would fundamentally suppress polysulfide shuttle, accelerate reaction kinetics, and simultaneously improve the electron / ion transport efficiency within the battery. Therefore, developing a lithium-sulfur battery catalyst that combines strong anchoring and high catalytic activity with ease of large-scale preparation is crucial for advancing lithium-sulfur batteries from the laboratory to practical applications. The 1,4-benzenedithiol-modified titanium dioxide / nickel hydroxide heterojunction catalyst proposed in this patent is an innovative solution to the aforementioned key issues. It aims to simultaneously achieve efficient adsorption and rapid conversion of polysulfides through material design and structural control, thereby significantly improving the cycle stability and rate performance of lithium-sulfur batteries. This has significant scientific value and broad application prospects. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a 1,4-benzenedithiol-modified titanium dioxide / nickel hydroxide heterojunction catalyst, which is particularly suitable as a membrane coating material for lithium-sulfur batteries. Compared to unmodified polypropylene (PP) membranes, the 1,4-benzenedithiol-modified titanium dioxide / nickel hydroxide heterojunction catalyst coated on the PP membrane surface not only adsorbs polysulfides but also improves the ion-electron transport efficiency inside the battery and effectively accelerates the conversion of polysulfides during the charging and discharging process of lithium-sulfur batteries. It also greatly suppresses polysulfide shuttle and improves the cycle stability of the battery.

[0007] This invention provides a method for preparing the above-mentioned 1,4-benzenedithiol modified titanium dioxide / nickel hydroxide heterojunction catalyst. The preparation process is simple, does not require reaction with molten sulfur, has low energy consumption, and has good prospects for industrial application.

[0008] To achieve the above technical objectives, the present invention adopts the following technical solution.

[0009] A method for preparing a 1,4-benzenedithiol-modified titanium dioxide / nickel hydroxide heterojunction catalyst comprises the following steps:

[0010] (1) Add titanium dioxide powder to a mixed solution of nickel nitrate hexahydrate and urea, and stir thoroughly to obtain a uniform suspension A;

[0011] (2) The suspension A obtained in step (1) was transferred to a closed container for hydrothermal treatment. After cooling to room temperature, it was taken out and filtered. The material was repeatedly rinsed with deionized water to obtain intermediate product A powder.

[0012] (3) Dissolve 1,4-benzenedithiol in anhydrous ethanol and sonicate to obtain a homogeneous suspension B;

[0013] (4) Add the intermediate product A powder obtained in step (2) to the uniform suspension B obtained in step (3) and stir evenly to obtain uniform suspension C;

[0014] (5) The suspension C obtained in step (4) is transferred to a sealed container, hydrothermally treated, and then washed with ethanol and deionized water to obtain a 1,4-benzenedithiol modified titanium dioxide / nickel hydroxide heterojunction catalyst.

[0015] Further, in step (1), the mass ratio of nickel nitrate hexahydrate to urea is 1:1 to 1:4, and the mass ratio of titanium dioxide powder to nickel nitrate hexahydrate is 1:2 to 1:5.

[0016] Preferably, the mass ratio of nickel nitrate hexahydrate to urea is 1:2 to 1:3.

[0017] Preferably, the mass ratio of titanium dioxide powder to nickel nitrate hexahydrate is 1:3 to 1:5.

[0018] Furthermore, in step (2), the hydrothermal treatment temperature is 155~180℃ and the hydrothermal treatment time is 120~720min.

[0019] Preferably, the hydrothermal treatment temperature is 160~170℃.

[0020] Preferably, the hydrothermal treatment time is 300~400 min.

[0021] Furthermore, in step (3), the mass-to-volume ratio of 1,4-benzenedithiol to anhydrous ethanol is 1g:150ml~1g:250ml; the ultrasonic time is more than 30min.

[0022] Preferably, the volume ratio of 1,4-benzenedithiol to anhydrous ethanol is 1g:180ml to 1g:220ml.

[0023] Furthermore, in step (4), the mass ratio of intermediate product A to 1,4-benzenedithiol in suspension B is 1:1 to 4:1.

[0024] Preferably, the mass ratio of intermediate product A to 1,4-benzenedithiol in the suspension B is 2:1 to 3:1.

[0025] Furthermore, in step (5), the hydrothermal treatment temperature is 70~100℃ and the hydrothermal treatment time is 100~160min.

[0026] Preferably, the hydrothermal treatment temperature is 80~90℃.

[0027] Preferably, the hydrothermal treatment time is 110~150 min.

[0028] The mechanism of this invention is as follows:

[0029] TiO2 loaded with Ni(OH)2 forms a TiO2 / Ni(OH)2 heterostructure. This structure utilizes a nanoscale interface to shorten the ion / electron transport path and leverages the self-generated field within the heterostructure to promote directional charge migration, effectively improving the charge transport efficiency of the heterostructure system. Furthermore, the organic sulfide 1,4-phenyldithiol is introduced to further optimize the material, resulting in a 1,4-phenyldithiol-modified titanium dioxide / nickel hydroxide heterostructure catalyst. The mercapto (-SH) functional group in 1,4-phenyldithiol can provide anchoring sites for polysulfides generated during the charging and discharging process of lithium-sulfur batteries.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) This invention provides a 1,4-benzenedithiol modified titanium dioxide / nickel hydroxide heterojunction material as a catalyst for lithium-sulfur batteries, thereby suppressing the shuttle effect of polysulfides, enhancing the ion-electron diffusion capability inside the battery, improving the cycle stability of the battery, and significantly improving the electrochemical performance of lithium-sulfur batteries.

[0032] (2) This invention differs from traditional lithium-sulfur battery catalyst materials by innovatively introducing the sulfur-containing organic compound 1,4-benzenedithiol. The thiol in this material contains thiol (-SH) functional groups, which not only provide anchoring sites for polysulfides generated during the charging and discharging process of lithium-sulfur batteries but also further enhance the material's ion-electron diffusion capability. Simultaneously, the lone pairs of electrons on the TiO2 surface in the TiO2 / Ni(OH)2 heterostructure, serving as the matrix, can form strong chemisorption with polysulfides, achieving efficient anchoring of polysulfides and providing active sites for polysulfide conversion, thereby improving the electrochemical performance of lithium-sulfur batteries. The Ni(OH)2 surface is rich in polar hydroxyl functional groups, which can anchor soluble polysulfides through strong chemical interactions and promote directional charge migration through the self-generated field within the heterojunction, effectively improving the charge transport efficiency of the heterojunction system. Attached Figure Description

[0033] Figure 1 The X-ray diffraction pattern of the 1,4-benzenedithiol modified titanium dioxide / nickel hydroxide heterojunction catalyst prepared in Example 1;

[0034] Figure 2 Transmission electron microscopy image of the 1,4-benzenedithiol modified titanium dioxide / nickel hydroxide heterojunction catalyst prepared in Example 1;

[0035] Figure 3 Scanning electron microscope image of a PP membrane coated with the 1,4-benzenedithiol modified titanium dioxide / nickel hydroxide heterojunction catalyst prepared in Example 1;

[0036] Figure 4 Comparison of rate performance of lithium-sulfur batteries coated with PP membranes using 1,4-benzenedithiol-modified titanium dioxide / nickel hydroxide heterojunction catalysts prepared in Examples 1-3;

[0037] Figure 5 The charge-discharge curves of lithium-sulfur batteries coated with PP membranes using the 1,4-benzenedithiol-modified titanium dioxide / nickel hydroxide heterojunction catalyst prepared in Examples 1-3 are compared. Detailed Implementation

[0038] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments. The described embodiments are not intended to limit the present invention. Any modifications or equivalent substitutions to the technical solution of the present invention that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the present invention.

[0039] Unless otherwise specified, all experimental instruments and reagents described below are commercially available.

[0040] Example 1: A 1,4-benzenedithiol-modified titanium dioxide / nickel hydroxide heterojunction catalyst was prepared by the following steps:

[0041] (1) 700 mg of nickel nitrate hexahydrate (Ni(NO3)2·6H2O) and 1500 mg of urea (CH4N2O) were dissolved in 70 ml of deionized water, and 150 mg of TiO2 powder was added. The mixture was stirred thoroughly to obtain a uniform suspension A.

[0042] (2) Place the suspension A obtained in step (1) into a polytetrafluoroethylene-lined stainless steel autoclave and keep it at 165 °C for 6 h in an oven. After cooling to room temperature, take it out, filter it, and repeatedly wash the material to obtain TiO2 / Ni(OH)2.

[0043] (3) Dissolve 70 mg of 1,4-benzenedithiol in 10 ml of anhydrous ethanol and sonicate for 15 min to obtain a uniform suspension B.

[0044] (4) Add 200 mg of TiO2 / Ni(OH)2 powder obtained in step (2) to suspension B obtained in step (3) and stir for 45 min to obtain suspension C;

[0045] (5) The suspension C obtained in step (4) is transferred to a polytetrafluoroethylene-lined stainless steel autoclave and treated at a constant temperature of 80 °C for 2 h. After rinsing with deionized water several times, the 1,4-benzenedithiol modified titanium dioxide / nickel hydroxide heterojunction catalyst is obtained.

[0046] The prepared catalyst was mixed with polyvinylidene fluoride (PVDF) at a mass ratio of 8:1, and N-methylpyrrolidone was added. After magnetic stirring for 4 hours, a uniform slurry was obtained. The slurry was then coated onto a PP membrane and dried at 80°C for 12 hours to obtain a PP membrane coated with a 1,4-benzenedithiol modified titanium dioxide / nickel hydroxide heterojunction catalyst.

[0047] Example 2: The difference between Example 2 and Example 1 is that in step (1), the amount of Ni(NO3)2·6H2O used is 600 mg and the amount of CH4N2O used is 1200 mg; in step (3), the amount of 1,4-benzenedithiol used is 50 mg.

[0048] Example 3: The difference between Example 3 and Example 1 is that in step (1), the amount of Ni(NO3)2·6H2O used is 500 mg and the amount of CH4N2O used is 1200 mg; in step (3), the amount of 1,4-benzenedithiol used is 30 mg.

[0049] The following analysis examines the performance of the catalysts prepared in Examples 1 and 2:

[0050] Figure 1 The X-ray diffraction pattern of the 1,4-benzenedithiol-modified titanium dioxide / nickel hydroxide heterojunction catalyst in Example 1 is shown in the figure. The pattern shows a good match between Example 1 and the standard card (#04-002-2751) for anatase TiO2. The diffraction peaks at 25.37, 37.95, 48.16, 54.10, and 55.21° correspond to the (001), (110), (111), and (003) crystal planes of TiO2, respectively. The diffraction peaks at 12.16, 33.66, 35.19, and 59.59° correspond to the α- The (001), (110), (111) and (300) crystal planes of Ni(OH)2 (PDF#00-022-0444) show that the diffraction peaks at 20.16, 22.2 and 27.98° are products of the combination of 1,4-benzenedithiol and Ni(OH)2, which proves the successful preparation of the 1,4-benzenedithiol modified titanium dioxide / nickel hydroxide heterojunction catalyst.

[0051] Figure 2 The image shows a transmission electron microscope (TEM) image of the 4-benzenedithiol-modified titanium dioxide / nickel hydroxide heterojunction catalyst in Example 11. As can be seen from the image, the catalyst is in the form of nanosheets with a diameter between 5 and 20 nm. This nanoscale structural feature effectively shortens the ion / electron transport path inside the material and can effectively improve the charge transport efficiency of the heterojunction system.

[0052] Figure 3 The image shows a cross-sectional scanning electron microscope (SEM) image of the 1,4-benzenedithiol-modified titanium dioxide / nickel hydroxide heterojunction catalyst prepared in Example 1 coated on a PP membrane. It can be seen that the catalyst layer supported on the membrane surface is continuous and dense, with a thickness of about 10 μm.

[0053] Figure 4 The rate performance of lithium-sulfur batteries assembled with PP separators coated with the 1,4-benzenedithiol-modified titanium dioxide / nickel hydroxide heterojunction catalyst prepared in Examples 1-3 is compared with that of lithium-sulfur batteries using blank separators. As can be seen from the figure, when the charge / discharge current density changes from 0.1C to 4C, the battery using the 1,4-benzenedithiol-modified titanium dioxide / nickel hydroxide heterojunction catalyst in Example 1 shows the highest positive electrode specific capacity at each current density, indicating that it has good rate performance.

[0054] Figure 5The figures show the charge-discharge curves of a lithium-sulfur battery assembled with a PP separator coated with the 1,4-benzenedithiol-modified titanium dioxide / nickel hydroxide heterojunction catalyst prepared in Examples 1-3, and a lithium-sulfur battery using a blank separator. As can be seen from the figures, the battery using the 1,4-benzenedithiol-modified titanium dioxide / nickel hydroxide heterojunction catalyst in Example 1 exhibits the lowest voltage polarization, indicating that it has good electrode reaction kinetics.

Claims

1. The application of a 1,4-benzenedithiol-modified titanium dioxide / nickel hydroxide heterojunction catalyst as a membrane coating material in lithium-sulfur batteries, characterized in that, The catalyst is prepared by in-situ growing 1,4-benzenedithiol molecules on a TiO2 / Ni(OH)2 heterojunction substrate to form interfacial chemical bonds. Utilizing the synergistic effect between the strong adsorption of the heterojunction and the catalytic activity of the organic sulfur molecules, the catalyst significantly enhances the anchoring and conversion capabilities of lithium polysulfide, an intermediate product in the cathode reaction of lithium-sulfur batteries. The specific steps include: (1) Add titanium dioxide powder to a mixed solution of nickel nitrate hexahydrate and urea, and stir thoroughly to obtain a uniform suspension A; (2) The suspension A obtained in step (1) was transferred to a closed container for hydrothermal treatment. After cooling to room temperature, it was taken out and filtered. The material was repeatedly rinsed with deionized water to obtain intermediate product A powder. (3) Dissolve 1,4-benzenedithiol in anhydrous ethanol and sonicate to obtain a homogeneous suspension B; (4) Add the intermediate product A powder obtained in step (2) to the uniform suspension B obtained in step (3) and stir evenly to obtain uniform suspension C; (5) The suspension C obtained in step (4) is transferred to a sealed container, hydrothermally treated, and then washed with ethanol and deionized water to obtain a 1,4-benzenedithiol modified titanium dioxide / nickel hydroxide heterojunction catalyst.

2. The preparation method of the 1,4-benzenedithiol modified titanium dioxide / nickel hydroxide heterojunction catalyst as described in claim 1, characterized in that, In step (1), the mass ratio of nickel nitrate hexahydrate to urea is 1:1 to 1:4; the mass ratio of titanium dioxide powder to nickel nitrate hexahydrate is 1:2 to 1:

5.

3. The preparation method of the 1,4-benzenedithiol modified titanium dioxide / nickel hydroxide heterojunction catalyst as described in claim 1, characterized in that, In step (2), the hydrothermal treatment temperature is 155~180℃ and the hydrothermal treatment time is 120~720min.

4. The preparation method of the 1,4-benzenedithiol modified titanium dioxide / nickel hydroxide heterojunction catalyst as described in claim 1, characterized in that, In step (3), the mass-to-volume ratio of 1,4-benzenedithiol to anhydrous ethanol is 1g:150ml~1g:250ml, and the ultrasonic treatment time is more than 30min.

5. The preparation method of the 1,4-benzenedithiol modified titanium dioxide / nickel hydroxide heterojunction catalyst as described in claim 1, characterized in that, In step (4), the mass ratio of intermediate product A to 1,4-benzenedithiol in suspension B is 1:1 to 4:

1.

6. The preparation method of the 1,4-benzenedithiol modified titanium dioxide / nickel hydroxide heterojunction catalyst as described in claim 1, characterized in that, In step (5), the hydrothermal treatment temperature is 70~100℃ and the hydrothermal treatment time is 100~160min.

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