Preparation method and application of catalytic material

Abstract

The invention discloses a preparation method and application of a catalytic material, and relates to the technical field of battery materials. The invention aims to solve the problems of complex preparation process, high cost, difficult realization of large-scale industrial production and poor cycling stability, charging and discharging efficiency and energy density of the lithium-sulfur battery of the existing lithium-sulfur battery positive electrode catalytic material. The catalytic material comprises seven elements of Li, Fe, Co, Ni, Mn, Zn and O, the morphology is a multilayer hollow spherical shell with a rough surface, the spherical shell is composed of polycrystalline particles with the particle size of 10-20 nm, the thickness of the outer spherical shell is 50 nm, the diameter of the outer spherical shell is 1-3 microns, a plurality of echo wall mode optical microcavities are formed among the spherical shells, and the spherical shell has typical traveling wave cavity characteristics; the material has a spinel structure, belongs to a cubic system, and has a space group of Fd-3m. The preparation method comprises the following steps: 1, preparing a precursor solution; 2, synthesizing a precursor; and 3, calcining. The catalytic material is used for preparing a lithium-sulfur battery positive electrode material.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, specifically to a method for preparing a catalytic material and its application. Background Technology

[0002] Lithium-sulfur batteries, with their ultra-high theoretical specific energy (2600Wh / kg), relatively low cost, and good environmental friendliness, have stood out among many new energy storage technologies and are widely recognized as one of the most promising next-generation energy storage technologies. However, in the process of commercialization, lithium-sulfur batteries face many challenging issues. Among them, the shuttle effect of lithium polysulfides and the slow redox kinetics are particularly prominent. During battery charging and discharging, lithium polysulfides readily dissolve in the electrolyte and repeatedly shuttle between the positive and negative electrodes. This not only leads to a significant loss of active materials but also causes rapid capacity decay and a substantial reduction in cycle stability. Simultaneously, the sluggish redox kinetics of lithium polysulfides severely restrict the battery's charge and discharge efficiency, resulting in poor rate performance.

[0003] To overcome these challenges, researchers have conducted extensive research, encompassing the design of unique electrode structures, the use of functional electrolyte additives, and the development of highly efficient cathode catalytic materials. Through their tireless efforts, significant progress has been made in the research of cathode catalytic materials for lithium-sulfur batteries. From early carbon-based materials to various metal compounds, and then to emerging single-atom catalysts and two-dimensional materials, different types of catalytic materials have demonstrated their unique advantages in suppressing the lithium polysulfide shuttle effect and accelerating redox kinetics. Through precise control of material structure and composition, as well as the synergistic effects of multiple materials, key performance indicators of lithium-sulfur batteries, such as cycle stability, charge-discharge efficiency, and energy density, have been significantly improved. However, the preparation processes of some catalytic materials are complex and costly, making large-scale industrial production difficult. Therefore, developing a novel cathode photoelectrochemical catalytic material for lithium-sulfur batteries is of significant practical importance and urgency. Summary of the Invention

[0004] The purpose of this invention is to solve the problems of complex preparation processes, high costs, and difficulty in large-scale industrial production of existing lithium-sulfur battery cathode catalyst materials, as well as the poor cycle stability, charge-discharge efficiency, and energy density of lithium-sulfur batteries. The invention provides a method for preparing a catalyst material and its application.

[0005] A method for preparing a catalytic material includes seven elements: Li, Fe, Co, Ni, Mn, Zn, and O. The material has a morphology of multi-layered hollow spherical shells with a rough surface. Each shell is composed of polycrystalline particles with a diameter of 10-20 nm. The outer shell is 50 nm thick and 1-3 μm in diameter. Multiple whispering-gallery mode optical microcavities are formed between the shells, exhibiting typical traveling-wave cavity characteristics. The catalytic material has a spinel structure, belongs to the cubic crystal system, and has a space group of Fd-3m. The preparation method is specifically carried out according to the following steps:

[0006] I. Preparation of precursor solution:

[0007] C6H 12 O6·H2O, LiNO3, Fe(NO3)2·9H2O, Co(NO3)2·6H2O, Ni(NO3)2·6H2O, Mn(NO3)2, and Zn(NO3)2·6H2O were added to deionized water and stirred magnetically until completely dissolved to obtain the precursor solution.

[0008] II. Synthetic precursors:

[0009] The precursor solution was poured into a high-pressure reactor, and the reactor was subjected to hydrothermal reaction at 180°C for a period of time to obtain the reaction product. The reaction product was washed and dried to obtain the precursor.

[0010] III. Calcination treatment:

[0011] The precursor is placed in a muffle furnace and heated to 500℃~600℃ in an air atmosphere. It is then annealed at 500℃~600℃ for a period of time and cooled to room temperature to obtain the catalyst material.

[0012] A catalytic material is used to prepare a cathode material for lithium-sulfur batteries, specifically by the following steps:

[0013] Multi-walled carbon nanotubes, sulfur, and catalytic materials were mixed and ground uniformly at a mass ratio of 2:7:1, and then melted at 150℃~160℃ for 10h~12h to obtain a composite material. The composite material, conductive carbon black, and polyvinylidene fluoride were mixed in N-methylpyrrolidone at a mass ratio of 8:1:1 to obtain a uniform suspension. The uniform suspension was dropped onto carbon cloth and then vacuum dried at 60℃~70℃ for 10h~12h to obtain a lithium-sulfur battery cathode material with a sulfur loading of 1 mg / cm²~5 mg / cm².

[0014] The total mass ratio of the composite material, conductive carbon black, and polyvinylidene fluoride to N-methylpyrrolidone is 100 mg: 2300 μL.

[0015] The beneficial effects of this invention are:

[0016] I. The catalytic material prepared by this invention includes seven elements: Li, Fe, Co, Ni, Mn, Zn, and O, which can provide various types of active centers. The coexistence of multiple metal elements can produce synergistic effects, and the electronic and geometric effects between different metal sites can mutually modulate each other, thereby optimizing the adsorption and activation capabilities of reactants.

[0017] II. The catalytic material prepared by this invention includes seven elements: Li, Fe, Co, Ni, Mn, Zn, and O. Among them, the electron exchange between the metals occupying the octahedral center provides a fast charge transfer channel and has good intrinsic electron / ion conduction ability.

[0018] III. One of the catalytic materials prepared by this invention is a p-type narrow bandgap semiconductor (E g = 1.03 eV), where the atomic ratio of Fe, Co, Ni, Mn, and Zn can be 4.79:10.69:6.01:4.85:7.65; electrons can more easily jump from the valence band to the conduction band, exhibiting good conductivity; at the same time, p-type semiconductors use holes as the main charge carriers, and the holes at the top of their valence band can form a charge delocalization effect with adsorbed polysulfides, reducing the energy barrier for Li⁺ insertion / extraction and thus accelerating the reaction kinetics;

[0019] IV. The catalytic material prepared by this invention has a morphology of a multi-layered hollow spherical shell with a rough surface. The spherical shell is composed of polycrystalline particles with a particle size of 10-20 nm. The outer spherical shell is 50 nm thick and has a diameter of 1-3 μm. When applied to the positive electrode host of lithium-sulfur batteries, it can simultaneously provide multiple positive effects such as physical confinement, chemical adsorption, and photo / electrocatalysis to the active material, thereby obtaining excellent catalytic performance.

[0020] V. The catalytic material prepared by this invention has a morphology of a multilayered hollow spherical shell with a rough surface. Multiple whispering-gallery mode optical microcavities are formed between the shells, exhibiting typical traveling wave cavity characteristics. The light signal undergoes continuous total internal reflection on the surface of the shell and is effectively confined inside the hollow shell, thereby inducing a localization effect. The multiple whispering-gallery mode optical microcavities in this material can significantly enhance the interaction between light and matter in the entire structure, and have the maximum absorption rate for 400 nm wavelength light.

[0021] VI. The catalytic material prepared by this invention exhibits highly sensitive response characteristics to light signals; under light irradiation, its adsorption capacity for Li2S6 is increased by 7 times compared with that under no light conditions;

[0022] VII. The catalytic material prepared by this invention is a porous material with a pore size distribution that covers almost the entire mesoporous range (2 nm to 50 nm), exhibiting good wettability to electrolytes; at the same time, it has a specific surface area of ​​65.08 m² / g, providing abundant active sites;

[0023] 8. The catalytic material prepared by this invention has a spinel structure (JCPDS#43-1003), belongs to the cubic crystal system, has a space group of Fd-3m, a cell parameter of 8.23 ​​Å, and interplanar spacings of (311) and (220) are 0.251 nm and 0.298 nm, respectively. This material has a strong chemical interaction with lithium polysulfide, an intermediate product of lithium-sulfur batteries, and can effectively suppress the fatal shuttle effect in lithium-sulfur batteries.

[0024] IX. In the catalytic material prepared by this invention, Fe, Co, and Ni on the surface all exhibit mixed valence states of +2 and +3, while Mn exhibits a mixed valence state of +2, +3, and +4; after adsorbing Li2S6, the high-valence metal ions (Co... 3+ Fe 3+ Ni 3+ Mn 4+ The proportion of ions will decrease significantly; the coexistence of multivalent ions provides a natural objective advantage for the regulation of electronic states, enabling precise modulation of the catalytic performance of materials.

[0025] 10. The catalytic material prepared by this invention has an ingenious preparation process, is simple and easy to operate, has excellent performance, and is conducive to commercial production;

[0026] XI. The catalytic material prepared by this invention is applied to the cathode material of lithium-sulfur batteries. In the light field, it can act as a photoreceiver and photocatalyst. Through photoexcitation, the photogenerated carriers enhance the interaction between light and materials by means of multi-cavity resonance effect, promote the redox reaction of lithium polysulfides, and suppress its shuttle effect, providing a new way to solve the inherent problems of lithium-sulfur batteries.

[0027] 12. The catalytic material prepared in this invention not only serves as a host for the sulfur cathode but also plays multiple key roles: on the one hand, it can efficiently anchor polysulfides and significantly improve their catalytic conversion kinetics; on the other hand, in a light field environment, this material can act as a light receiver and photocatalyst, enhancing the interaction between light and material through multi-cavity resonance effects, greatly improving the light energy collection and absorption efficiency; driven by photocarriers, it can promote the electrochemical reaction of sulfur over a wide incident angle range; at a low rate of 0.1C, the battery exhibits a capacity of 1546.4 mAh g⁻¹. -1 Its high specific capacity, even at a high rate of 5C, still maintains 897.5mAh g. -1 It has the capacity while achieving a photoelectric energy conversion efficiency of up to 15.6%. Attached Figure Description

[0028] Figure 1 This is a flowchart illustrating the preparation process of a catalytic material prepared in Example 1.

[0029] Figure 2Scanning electron microscope image of the precursor prepared in Example 1;

[0030] Figure 3 A scanning electron microscope image of a catalytic material prepared in Example 1;

[0031] Figure 4 A transmission electron microscope image of a catalytic material prepared in Example 1;

[0032] Figure 5 This is a magnified transmission electron microscope image of a catalytic material prepared in Example 1;

[0033] Figure 6 Selective electron diffraction image of a catalytic material prepared in Example 1;

[0034] Figure 7 This is a high-resolution transmission electron microscope image of a catalytic material prepared in Example 1;

[0035] Figure 8 This is an elemental distribution image of a catalytic material prepared in Example 1;

[0036] Figure 9 The atomic percentage of a catalytic material prepared in Example 1 was obtained by energy dispersive spectroscopy measured in a scanning electron microscope system.

[0037] Figure 10 The X-ray diffraction pattern of a catalytic material prepared in Example 1 and the Rieteld-refined X-ray diffraction pattern are shown below.

[0038] Figure 11 The nitrogen adsorption-desorption isotherm and pore size distribution curve of a catalytic material prepared in Example 1 are shown.

[0039] Figure 12 The image shows the Motter-Schottky curve of a catalytic material prepared in Example 1.

[0040] Figure 13 The UV-Vis diffuse reflectance spectrum of a catalytic material prepared in Example 1 and the Tauc diagram derived therefrom are shown.

[0041] Figure 14 A catalytic material prepared in Example 1 was used at 37.71 mW / cm². -2 Transient photocurrent response diagram obtained under light intensity;

[0042] Figure 15 COMSOL optical simulation of a catalytic material prepared in Example 1; in (a), I, II, III and IV represent wavelengths of 394, 400, 402.3 and 406.8 nm, respectively. zCross-sectional view (where E) z (a) is the z-component of the electric field; (b) is the absorption spectrum (red dot) and amplitude of the electric field |E| (blue dot) of a single catalytic material structure prepared in Example 1 obtained by COMSOL simulation, and |E| (green solid line) calculated using CMT; (c) is the effect of the 400 nm incident angle on |E| within the structure;

[0043] Figure 16 The ultraviolet-visible spectra of Li2S6 after adding a catalytic material prepared in Example 1 at different times and when the sample temperature slowly rises from 18 °C to 21 °C are used to simulate the photothermal effect;

[0044] Figure 17 The UV-Vis spectra of Li₂S₆ solution after adding a catalytic material prepared in Example 1 are shown in the figures: (a) adsorption effect; (b) light irradiation effect; (c) UV-Vis spectrum of pure Li₂S₆ solution under light irradiation. Illustrations: corresponding digital photographs of the Li₂S₆ adsorption results;

[0045] Figure 18 A schematic diagram illustrating the thermal imaging principle of a catalytic material prepared in Example 1 under illumination;

[0046] Figure 19 XPS spectra before and after Li₂S₆ adsorption, (e)Fe 2p 3 / 2 (f)Co 2p 3 / 2 , (g) Ni 2p 3 / 2 (h)Mn2p 3 / 2 ;

[0047] Figure 20 The following are the kinetic properties of a catalytic material prepared in Example 1; (a) a schematic diagram of a photo-assisted lithium-sulfur battery; (b) electrochemical impedance spectroscopy (EIS) of the battery prepared in Example 1 under light and dark conditions; (c) CV curves; (d, e) Tafel slopes in regions A and B of (c); (f, g) values ​​in the range of 0.1–0.5 mV / s. -1 The CV curve of a catalytic material battery prepared in Example 1 at the scan rate; (h) is the Li on the photoelectric cathode of the catalytic material prepared in Example 1. + The diffusion coefficient; (i) is the diffusion coefficient at 2 mV s. -1 CV curves of a Li2S6 symmetric cell at scan rate; (j, k) are Li2S nucleation curves of a photoelectrode of a catalytic material prepared in Example 1 under light and dark conditions;

[0048] Figure 21 A battery prepared using a catalyst material prepared in Example 1 was tested under (a) light and (b) dark conditions at a scan rate of 0.1 ~ 0.5 mV s. -1CV curve at time;

[0049] Figure 22 To utilize Figure 21 The linear relationship between peak current intensity and the square root of scan rate was calculated for peaks I, II, and III under (a) illumination and (b) dark conditions.

[0050] Figure 23 A catalytic material prepared in Example 1 under light and dark conditions (a) Li2S and Li2S n (a) The relative activation energy of S8 and Li2S; (b) The relative activation energy of S8 and Li2S;

[0051] Figure 24 The electrochemical performance evaluation of a catalytic material prepared in Example 1 includes: (a) rate performance under light and dark conditions; (b) capacity conversion efficiency at different current densities; (c) long-cycle stability of the battery under alternating light and dark conditions at 1C; (d) charge-discharge curves for the 58th cycle (dark) and the 60th cycle (light); and (e) high sulfur loading at 5 mg / cm³. -2 (f) Cyclic performance of the photocathode under 0.5C dark and light conditions; (g) Charge-discharge curves of a battery prepared from a catalytic material prepared in Example 1 (Region I: Discharge, Region II: Photocharging for 1.5 hours, Region III: Discharge).

[0052] Figure 25 The charge-discharge curves of batteries prepared from a catalytic material prepared in Example 1 under different current densities under (a) light and (b) dark conditions are shown.

[0053] Figure 26 The cycling stability of a battery prepared from a catalyst material prepared in Example 1 under alternating light and dark conditions at a current density of 0.5C.

[0054] Figure 27 For in-situ characterization of a catalytic material prepared in Example 1; (a, d) Schematic diagram of in-situ Raman device; (b, e) Charge-discharge curves; (c, f) Raman spectrum contour plots under light and dark conditions;

[0055] Figure 28 For mechanism analysis; (a, c) are internal mechanism diagrams of a battery containing a catalytic material prepared in Example 1; (b) a catalytic material prepared in Example 1 and Li2S / S8 with Li + / Li energy diagram (SRR represents sulfur reduction reaction, SER represents sulfur evolution reaction). Detailed Implementation

[0056] Specific Implementation Method 1: This implementation method discloses a method for preparing a catalytic material. The catalytic material comprises seven elements: Li, Fe, Co, Ni, Mn, Zn, and O. Its morphology is a multi-layered hollow spherical shell with a rough surface. The spherical shell is composed of polycrystalline particles with a particle size of 10-20 nm. The outer spherical shell is 50 nm thick and has a diameter of 1-3 μm. Multiple whispering-gallery mode optical microcavities are formed between the spherical shells, exhibiting typical traveling-wave cavity characteristics. The catalytic material has a spinel structure, belongs to the cubic crystal system, and has a space group of Fd-3m. The preparation method is specifically carried out according to the following steps:

[0057] I. Preparation of precursor solution:

[0058] C6H 12 O6·H2O, LiNO3, Fe(NO3)2·9H2O, Co(NO3)2·6H2O, Ni(NO3)2·6H2O, Mn(NO3)2, and Zn(NO3)2·6H2O were added to deionized water and stirred magnetically until completely dissolved to obtain the precursor solution.

[0059] II. Synthetic precursors:

[0060] The precursor solution was poured into a high-pressure reactor, and the reactor was subjected to hydrothermal reaction at 180°C for a period of time to obtain the reaction product. The reaction product was washed and dried to obtain the precursor.

[0061] III. Calcination treatment:

[0062] The precursor is placed in a muffle furnace and heated to 500℃~600℃ in an air atmosphere. It is then annealed at 500℃~600℃ for a period of time and cooled to room temperature to obtain the catalyst material.

[0063] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that: the C6H mentioned in step one... 12 The mass ratio of O6·H2O to the volume ratio of deionized water is (4g~6g):50mL. Other steps are the same as in Specific Implementation Method 1.

[0064] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that the mass ratio of LiNO3 to deionized water in step one is (0.1g~0.2g):50mL. The other steps are the same as in Specific Implementation Method One or Two.

[0065] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the mass ratio of Fe(NO3)2·9H2O to the volume ratio of deionized water in step one is (0.1g~0.2g):50mL. The other steps are the same as in Specific Implementation Methods One to Three.

[0066] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that the mass ratio of Co(NO3)2·6H2O to the volume ratio of deionized water in step one is (1g~2g):50mL. The other steps are the same as in Specific Implementation Methods One to Four.

[0067] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that the mass ratio of Ni(NO3)2·6H2O to the volume ratio of deionized water in step one is (0.5g~1.5g):50mL. The other steps are the same as in Specific Implementation Methods One to Five.

[0068] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in the following ways: the mass ratio of Mn(NO3)2 to deionized water in step one is (1.5g~2.5g):50mL; the mass ratio of Zn(NO3)2·6H2O to deionized water in step one is (0.2g~0.4g):50mL; the Mn(NO3)2 in step one is a 50% aqueous solution; and the magnetic stirring speed in step one is 1500rpm~2000rpm. Other steps are the same as in Specific Implementation Methods One to Six.

[0069] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in the following ways: the hydrothermal reaction time in step two is 6 to 8 hours; the reaction product is washed sequentially with ultrapure water, anhydrous ethanol, and lithium nitrate solution, each time 1 to 3 times; the concentration of the lithium nitrate solution is 0.1 mol / L to 0.5 mol / L; the drying temperature in step two is 60°C to 80°C, and the drying time is 5 to 24 hours. Other steps are the same as in Specific Implementation Methods One to Seven.

[0070] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that: the annealing time at 500℃~600℃ in step three is 1h~2h; the heating rate in step three is 1℃ / min~2℃ / min. The other steps are the same as in Specific Implementation Methods One to Eight.

[0071] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods One to Nine in that the preparation of the lithium-sulfur battery cathode material is carried out according to the following steps:

[0072] Multi-walled carbon nanotubes, sulfur, and catalytic materials were mixed and ground uniformly at a mass ratio of 2:7:1, and then melted at 150℃~160℃ for 10h~12h to obtain a composite material. The composite material, conductive carbon black, and polyvinylidene fluoride were mixed in N-methylpyrrolidone at a mass ratio of 8:1:1 to obtain a uniform suspension. The uniform suspension was dropped onto carbon cloth and then vacuum dried at 60℃~70℃ for 10h~12h to obtain a lithium-sulfur battery cathode material with a sulfur loading of 1 mg / cm²~5 mg / cm².

[0073] The total mass ratio of the composite material, conductive carbon black, and polyvinylidene fluoride to N-methylpyrrolidone is 100 mg: 2300 μL. Other steps are the same as in embodiments one through nine.

[0074] The beneficial effects of the present invention are verified using the following embodiments:

[0075] Example 1: A method for preparing a catalytic material, specifically comprising the following steps:

[0076] I. Preparation of precursor solution:

[0077] 5 grams of C6H 12 O6·H2O (Aladdin, analytical grade), 0.173 g LiNO3 (Aladdin, analytical grade), 0.101 g Fe(NO3)2·9H2O (Aladdin, analytical grade), 1.455 g Co(NO3)2·6H2O (Aladdin, analytical grade), 0.727 g Ni(NO3)2·6H2O (Aladdin, analytical grade), 1.79 g Mn(NO3)2 (Sinopharm, analytical grade, 50% aqueous solution) and 0.372 g Zn(NO3)2·6H2O (Aladdin, analytical grade) were added to deionized water and magnetically stirred until completely dissolved to obtain the precursor solution.

[0078] The magnetic stirring speed mentioned in step one is 1500 rpm;

[0079] II. Synthetic precursors:

[0080] The precursor solution was poured into a high-pressure reactor, and the reactor was subjected to hydrothermal reaction at 180°C for 400 minutes to obtain the reaction product. The reaction product was washed and then dried at 70°C for 12 hours to obtain the precursor.

[0081] In step two, the reaction product is washed sequentially with ultrapure water, anhydrous ethanol, and lithium nitrate solution, each time twice; the concentration of the lithium nitrate solution is 0.3 mol / L.

[0082] III. Calcination treatment:

[0083] The precursor was placed in a muffle furnace and heated to 500°C in an air atmosphere. It was then annealed at 500°C for 1 hour and cooled to room temperature to obtain the catalyst material.

[0084] The heating rate described in step three is 1℃ / min.

[0085] Figure 2 Scanning electron microscope image of the precursor prepared in Example 1;

[0086] from Figure 2 As can be seen, the precursor has a spherical morphology.

[0087] Figure 3 A scanning electron microscope image of a catalytic material prepared in Example 1;

[0088] Figure 4 A transmission electron microscope image of a catalytic material prepared in Example 1;

[0089] Figure 5 This is a magnified transmission electron microscope image of a catalytic material prepared in Example 1;

[0090] Figure 6 Selective electron diffraction image of a catalytic material prepared in Example 1;

[0091] Figure 7 This is a high-resolution transmission electron microscope image of a catalytic material prepared in Example 1;

[0092] Figure 8 This is an elemental distribution image of a catalytic material prepared in Example 1;

[0093] Figure 9 The atomic percentage of a catalytic material prepared in Example 1 was obtained by energy dispersive spectroscopy measured in a scanning electron microscope system.

[0094] from Figure 3-9 It is known that the catalytic material prepared in Example 1 has a hollow, multi-layered spherical morphology with a rough surface and tiny protrusions at the tip; the size is 1-3 μm, and it is formed by the self-assembly of 10-20 nm nanocrystals to form a porous spherical shell with a thickness of about 50 nm. Clear and uniformly spaced lattice stripes indicate that the catalytic material prepared in Example 1 has excellent crystallinity, showing identifiable (311) and (220) planes, with interplanar spacings of 0.251 nm and 0.298 nm, respectively. In addition, the Fe, Co, Ni, Mn, Zn, and O elements in this novel catalytic material are uniformly distributed, and the atomic percentages of each element are Fe:Co:Ni:Mn:Zn:O = 4.79:10.69:6.01:4.85:7.65:66.01.

[0095] Figure 10 The X-ray diffraction pattern of a catalytic material prepared in Example 1 and the Rieteld-refined X-ray diffraction pattern are shown below.

[0096] from Figure 10 It is known that the catalytic material prepared in Example 1 has a pure spinel peak. Compared with the Co3O4 standard card (JCPDS#43-1003), the peak of the catalytic material prepared in Example 1 shifts to a negative angle by about 0.9° due to the larger average radius of the introduced metal ions and the lattice expansion caused by stress. Rietveld refinement results show that this novel catalytic material belongs to the Fd-3m space group with a unit parameter of 8.23 ​​Å.

[0097] Figure 11 The nitrogen adsorption-desorption isotherm and pore size distribution curve of a catalytic material prepared in Example 1 are shown.

[0098] from Figure 11 As can be seen, the nitrogen adsorption-desorption isotherm exhibits typical characteristics of mesoporous materials, with a pore size distribution spanning almost the entire mesoporous range (2nm-50nm) and a specific surface area of ​​65.08m². 2 g -1 The relatively large specific surface area and abundant porous structure of this catalytic material provide more active sites, which is beneficial for electrolyte penetration and ion diffusion.

[0099] Figure 12 The image shows the Motter-Schottky curve of a catalytic material prepared in Example 1.

[0100] Figure 13 The UV-Vis diffuse reflectance spectrum of a catalytic material prepared in Example 1 and the Tauc diagram derived therefrom are shown.

[0101] Figure 14 A catalytic material prepared in Example 1 was used at 37.71 mW / cm². -2 Transient photocurrent response diagram obtained under light intensity;

[0102] from Figure 12-14 As can be seen, the electronic structure of the catalytic material prepared in Example 1 was analyzed using Mott-Schottky curves. A negative slope was observed, indicating p-type semiconductor behavior; the flat band potential (E) FB ) is 2.30V (vs. Li + / Li), derived from the intercept with the horizontal axis; for p-type semiconductors, E FB Generally located in the price band (E) VB At 0.1V above; therefore, the E of this catalyst material VBIt should be 2.40V; To evaluate the light-harvesting potential, the optical bandgap characteristics of this catalytic material as a semiconductor were further studied using ultraviolet-visible diffuse reflectance spectroscopy. The bandgap was calculated to be as low as 1.03eV using the Tauc plot method. The relatively narrow bandgap allows electrons in the valence band to be rapidly excited into the conduction band under illumination, generating photoelectrons and photoholes, which further improves the conductivity. The photocurrent response test showed that the photoelectrode of the catalytic material prepared in Example 1 had a significant photocurrent response, indicating that it has high sensitivity to light signals and thus high photoelectric energy conversion efficiency.

[0103] Figure 15 COMSOL optical simulation of a catalytic material prepared in Example 1; in (a), I, II, III and IV represent wavelengths of 394, 400, 402.3 and 406.8 nm, respectively. z Cross-sectional view (where E) z (a) is the z-component of the electric field; (b) is the absorption spectrum (red dot) and amplitude of the electric field |E| (blue dot) of a single catalytic material structure prepared in Example 1 obtained by COMSOL simulation, and |E| (green solid line) calculated using CMT; (c) is the effect of the 400 nm incident angle on |E| within the structure;

[0104] from Figure 15 To understand how the catalytic material prepared in Example 1 exhibits excellent photocatalytic performance and photoelectric energy conversion efficiency under illumination, the absorption spectrum and electric field amplitude |E| of the novel catalytic material structure were simulated using the commercial finite element simulation software COMSOL Multiphysics. The z-direction (E|) at four specific wavelengths—I (394 nm), II (400 nm), III (402.3 nm), and IV (406.8 nm)—were analyzed. z The electric field distribution of the catalytic material prepared in Example 1, and the corresponding adsorption spectrum and electric field amplitude |E|, are shown. Except for 394 nm, the E values ​​in the structure of the catalytic material are as follows: zExhibiting typical traveling-wave cavity characteristics with an ordered electric field distribution, this phenomenon indicates that light undergoes continuous total internal reflection at its surface, effectively localizing the light field within the structure. Optically, this total internal reflection-induced localization effect is caused by multiple whispering-gallery modes of optical microcavities formed within the structure. Resonant coupling was observed at wavelengths (II, III, IV). The resonant coupling effect at specific wavelengths allows light to not only exist in the outer film layer but also be transferred to more inner film layers through coupling. This multi-cavity resonance significantly enhances the light-matter interaction of the entire structure, thereby greatly improving light absorption and photocatalytic performance. Notably, maximum absorbance and |E| were observed at a wavelength of 400 nm. Furthermore, the effect of the incident light angle at 400 nm on |E| within the film structure was analyzed; the maximum |E| was observed within the cavity when the incident angle was 0° (perpendicular incident angle). More interestingly, high |E| can also be obtained over a wide angle range of 0–80°, meaning that light can promote sulfur electrochemistry over a wide incident angle range.

[0105] Figure 16 The ultraviolet-visible spectra of Li2S6 after adding a catalytic material prepared in Example 1 at different times and when the sample temperature slowly rises from 18 °C to 21 °C are used to simulate the photothermal effect;

[0106] Figure 17 The UV-Vis spectra of Li₂S₆ solution after adding a catalytic material prepared in Example 1 are shown in the figures: (a) adsorption effect; (b) light irradiation effect; (c) UV-Vis spectrum of pure Li₂S₆ solution under light irradiation. Illustrations: corresponding digital photographs of the Li₂S₆ adsorption results;

[0107] Figure 18 A schematic diagram illustrating the thermal imaging principle of a catalytic material prepared in Example 1 under illumination;

[0108] from Figure 16-18 To evaluate the effect of light irradiation on the anchoring of polysulfides by the catalytic material prepared in Example 1, visual adsorption measurements were performed under different light irradiation times and no-light conditions. The mixed solution of the catalytic material prepared in Example 1 and Li₂S₆ required 3.5 h to become completely clear under no-light conditions. However, under light irradiation, the color of the Li₂S₆ solution gradually lightened with increasing irradiation time, becoming essentially transparent within 30 min, indicating a gradual decrease in the concentration of Li₂S₆ in the solution. These results demonstrate that the adsorption time was significantly shortened, proving that light irradiation promoted the adsorption of Li₂S₆ by this novel catalytic material. Furthermore, this verifies, from two aspects, the possibility of light irradiation and photothermal effects promoting the decomposition of Li₂S₆ molecules has been ruled out.

[0109] Figure 19 XPS spectra before and after Li₂S₆ adsorption, (e)Fe 2p3 / 2 (f)Co 2p 3 / 2 , (g) Ni 2p 3 / 2 (h)Mn2p 3 / 2 ;

[0110] from Figure 19 As can be seen, in order to further study the interaction between the catalytic material prepared in Example 1 and polysulfides, we analyzed its X-ray photoelectron spectra before and after interaction with Li2S6, and the high-valence Fe... 3+ The proportion of Fe decreased sharply from 54% to 21%, and the Fe 2p energy spectrum showed a negative shift in binding energy. Similar phenomena were observed in Co 2p, Ni 2p, and Mn 2p, confirming that Li₂S₆ donated electrons to Fe, Co, Ni, and Mn. These results indicate a strong chemical interaction between Li₂S₆ and this novel catalytic material.

[0111] Electrochemical performance testing:

[0112] 1. Electrode preparation:

[0113] 40 mg of multi-walled carbon nanotubes (MWCNTs), 140 mg of sulfur, and 20 mg of the catalyst material prepared in Example 1 were mixed and ground uniformly, and then melted at 155 °C for 12 h to obtain a composite material. The composite material, conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) were mixed in N-methylpyrrolidone (NMP) at a mass ratio of 8:1:1 to obtain a uniform suspension. The uniform suspension was dropped onto carbon cloth (CC) with a diameter of 13 mm and then vacuum dried at 60 °C for 12 h to obtain a lithium-sulfur battery cathode material with a sulfur loading of 1.5 mg / cm².

[0114] The total mass ratio of the composite material, conductive carbon black, and polyvinylidene fluoride to N-methylpyrrolidone is 100 mg: 2300 μL.

[0115] 2. Assembly and electrochemical testing of lithium-sulfur batteries:

[0116] Using the lithium-sulfur battery cathode material prepared above as the cathode, lithium sheet as the anode, and single-layer polypropylene (Celgard 2400) as the separator, a CR2032 cathode shell with a 5 mm hole in the middle was used, and the hole was sealed with PET tape to prepare a lithium-sulfur battery with a light incident window. The electrolyte used was 30 μL of 1.0 M lithium bis(trifluoromethane)sulfonylimide (LiTFSI) in a DOL / DME (volume ratio 1:1) mixed solution containing 2 wt% LiNO3, and the electrolyte-to-sulfur ratio was 20 μL / mg.

[0117] The assembled lithium-sulfur batteries were tested for charge-discharge performance under the same test conditions. Constant current charge-discharge (GCD) tests were performed on the LANCT battery test system at different rates within a voltage range of 1.7 to 2.8 V at room temperature. Cyclic voltammetry (CV) measurements were performed between 1.7 and 2.8 V using a VMP3 multichannel electrochemical workstation (BioLogic, France).

[0118] Figure 20 The following are the kinetic properties of a catalytic material prepared in Example 1; (a) a schematic diagram of a photo-assisted lithium-sulfur battery; (b) electrochemical impedance spectroscopy (EIS) of the battery prepared in Example 1 under light and dark conditions; (c) CV curves; (d, e) Tafel slopes in regions A and B of (c); (f, g) values ​​in the range of 0.1–0.5 mV / s. -1 The CV curve of a catalytic material battery prepared in Example 1 at the scan rate; (h) is the Li on the photoelectric cathode of the catalytic material prepared in Example 1. + The diffusion coefficient; (i) is the diffusion coefficient at 2 mV s. -1 CV curves of a Li2S6 symmetric cell at scan rate; (j, k) are Li2S nucleation curves of a photoelectrode of a catalytic material prepared in Example 1 under light and dark conditions;

[0119] like Figure 20 As shown, a detailed assembly diagram of the photo-assisted lithium-sulfur battery is presented. The redox kinetics under both photo-assisted and non-photo-assisted conditions are compared using electrochemical impedance spectroscopy (EIS), CV testing, variable sweep CV, symmetric CV, and Li₂S nucleation tests. Analysis of the test results shows that, compared to the non-photo-assisted condition, the charge transfer resistance is reduced by 52.3% under photo-assisted conditions, the peak area covered by CV is increased by 22.42%, Li₂S deposition time is earlier, the peak current is larger, and the deposition capacity is greater. This further confirms that photogenerated carriers help reduce charge transfer resistance, accelerate charge transfer rate, and speed up the redox reaction process, thereby improving its electrochemical performance.

[0120] Figure 21 A battery prepared using a catalyst material prepared in Example 1 was tested under (a) light and (b) dark conditions at a scan rate of 0.1 ~ 0.5 mV s. -1 CV curve at time;

[0121] Figure 22 To utilize Figure 21 The linear relationship between peak current intensity and the square root of scan rate was calculated for peaks I, II, and III under (a) illumination and (b) dark conditions.

[0122] Figure 23A catalytic material prepared in Example 1 under light and dark conditions (a) Li2S and Li2S n (a) The relative activation energy of S8 and Li2S; (b) The relative activation energy of S8 and Li2S;

[0123] like Figure 21-23 As shown, the area under the CV curve increases with increasing scan rate, which was confirmed under both illuminated and unilluminated conditions. This indicates that the photo-assisted effect can improve the specific capacity of the battery and enhance its redox reaction kinetics. Furthermore, the peak current intensity exhibits a linear relationship with the square root of the scan rate. Using this relationship, the lithium-ion diffusion coefficient was calculated according to the Randles-Sevcik equation. A larger lithium-ion diffusion coefficient was obtained under illuminated conditions, indicating a significant enhancement in charge transfer and lithium-ion diffusion capabilities within the battery. A lower activation energy is beneficial for accelerating the conversion reaction of polysulfides; under illuminated conditions, S8 is converted to Li2S. n E a The value was 27.48 kJ / mol lower than that under conditions without added light. -1 This indicates that Li2S n The formation rate is accelerated. Subsequently, the long-chain Li2S4 is reduced to the short-chain Li2S2 / Li2S, and the addition of light leads to E a The value decreased by 46.68 kJ / mol. -1 This significantly increased the rate of Li₂S₄ reduction to Li₂S. During the charging process, under illumination, Li₂S was oxidized to Li₂S. n E a The value decreased by 56.81 kJ / mol compared to the condition without added light. -1 This leads to the rapid oxidation of deposited Li2S. In summary, illumination can promote the redox process in both kinetic and dynamic aspects.

[0124] Figure 24 An evaluation of the electrochemical performance of a catalytic material prepared in Example 1; (a) rate performance under light and dark conditions; (b) capacity conversion efficiency at different current densities; (c) long-cycle stability of the battery under alternating light and dark conditions at 1C; (d) charge-discharge curves for the 58th cycle (dark) and the 60th cycle (light); (e) high sulfur loading of 5 mg / cm³. -2 (f) Cyclic performance of the photocathode under 0.5C dark and light conditions; (g) Charge-discharge curves of a battery prepared from a catalytic material prepared in Example 1 (Region I: Discharge, Region II: Photocharging for 1.5 hours, Region III: Discharge).

[0125] Figure 25 The charge-discharge curves of batteries prepared from a catalytic material prepared in Example 1 under different current densities under (a) light and (b) dark conditions are shown.

[0126] Figure 26 The cycling stability of a battery prepared from a catalyst material prepared in Example 1 under alternating light and dark conditions at a current density of 0.5C.

[0127] like Figure 24-26 As shown, the catalytic material prepared in Example 1 exhibited excellent performance in rate performance, capacity conversion efficiency, long-cycle alternating light and dark conditions (0.5C and 1C), and charge-discharge curves under illumination. Furthermore, it performed well under a sulfur loading of 5 mg / cm³. -2 Low liquid sulfur ratio 4.5 μL mg -1 Even under these conditions, it still maintains a high capacity retention rate of 91.01% after 80 cycles (the capacity retention rate is 87.51% without light), and the calculated photoelectric energy conversion efficiency is 15.6%. Compared with existing research on photo-assisted lithium-sulfur batteries, the photo-assisted lithium-sulfur battery prepared with a catalytic material in Example 1 exhibits the highest photoelectric energy conversion efficiency.

[0128] Figure 27 For in-situ characterization of a catalytic material prepared in Example 1; (a, d) Schematic diagram of in-situ Raman device; (b, e) Charge-discharge curves; (c, f) Raman spectrum contour plots under light and dark conditions;

[0129] Figure 28 For mechanism analysis; (a, c) are internal mechanism diagrams of a battery containing a catalytic material prepared in Example 1; (b) a catalytic material prepared in Example 1 and Li2S / S8 with Li + / Li energy diagram (SRR represents sulfur reduction reaction, SER represents sulfur evolution reaction).

[0130] like Figure 27-28 As shown, the polysulfide conversion process during charging and discharging under both illuminated and unilluminated conditions was analyzed in detail using advanced in-situ Raman spectroscopy. The results show that under illuminated conditions, S8 is converted into more long-chain polysulfides earlier during discharge, and the polysulfides are completely converted to Li2S at 1.7 V at the end of discharge. Under unilluminated conditions, polysulfides still exist at 1.7 V at the end of discharge, and the conversion is not complete. During charging, under illuminated conditions, Li2S is converted into polysulfides earlier and completely converted to S8. In addition, a novel catalytic material prepared in Example 1 and the Li2S / S8 and Li... +Energy diagram analysis of / Li shows that its band structure completely covers the 1.9–2.3 V potential range of the sulfur electrochemical redox reaction, indicating that photogenerated holes directionally promote the oxidation process, while photogenerated electrons promote the reduction process. In summary, photogenerated electrons in the conduction band and photogenerated holes in the valence band enhance the rapid redox reaction of polysulfides under illumination, accelerate the redox kinetics of polysulfides, mitigate the shuttle effect of polysulfides, and improve the overall energy storage performance.

[0131] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a catalytic material, characterized in that... The catalytic material comprises seven elements: Li, Fe, Co, Ni, Mn, Zn, and O. Its morphology is a multi-layered hollow spherical shell with a rough surface. Each shell is composed of polycrystalline particles with a diameter of 10-20 nm. The outer shell is 50 nm thick and 1-3 μm in diameter. Multiple whispering-gallery mode optical microcavities are formed between the shells, exhibiting typical traveling-wave cavity characteristics. The catalytic material has a spinel structure, belongs to the cubic crystal system, and has a space group of Fd-3m. The preparation method is specifically carried out according to the following steps: I. Preparation of precursor solution: C6H 12 O6·H2O, LiNO3, Fe(NO3)2·9H2O, Co(NO3)2·6H2O, Ni(NO3)2·6H2O, Mn(NO3)2, and Zn(NO3)2·6H2O were added to deionized water and stirred magnetically until completely dissolved to obtain the precursor solution. II. Synthetic precursors: The precursor solution was poured into a high-pressure reactor, and the reactor was subjected to hydrothermal reaction at 180°C for a period of time to obtain the reaction product. The reaction product was washed and dried to obtain the precursor. III. Calcination treatment: The precursor is placed in a muffle furnace and heated to 500℃~600℃ in an air atmosphere. It is then annealed at 500℃~600℃ for a period of time and cooled to room temperature to obtain the catalyst material.

2. The method for preparing a catalytic material according to claim 1, characterized in that... The C6H mentioned in step one 12 The mass ratio of O6·H2O to the volume ratio of deionized water is (4g~6g):50mL.

3. The method for preparing a catalytic material according to claim 1, characterized in that... The mass ratio of LiNO3 to deionized water in step one is (0.1g~0.2g):50mL.

4. The method for preparing a catalytic material according to claim 1, characterized in that... The mass ratio of Fe(NO3)2·9H2O to the volume ratio of deionized water in step one is (0.1g~0.2g):50mL.

5. The method for preparing a catalytic material according to claim 1, characterized in that... The mass ratio of Co(NO3)2·6H2O to the volume ratio of deionized water in step one is (1g~2g):50mL.

6. The method for preparing a catalytic material according to claim 1, characterized in that... The mass ratio of Ni(NO3)2·6H2O to the volume ratio of deionized water in step one is (0.5g~1.5g):50mL.

7. The method for preparing a catalytic material according to claim 1, characterized in that... The mass ratio of Mn(NO3)2 to deionized water in step one is (1.5g~2.5g):50mL; the mass ratio of Zn(NO3)2·6H2O to deionized water in step one is (0.2g~0.4g):50mL; the Mn(NO3)2 in step one is a 50% aqueous solution; the magnetic stirring speed in step one is 1500rpm~2000rpm.

8. The method for preparing a catalytic material according to claim 1, characterized in that... The hydrothermal reaction time in step two is 6h~8h; the reaction product is washed with ultrapure water, anhydrous ethanol and lithium nitrate solution in step two, each time 1 to 3 times; the concentration of the lithium nitrate solution is 0.1mol / L~0.5mol / L; the drying temperature in step two is 60℃~80℃ and the drying time is 5h~24h.

9. The method for preparing a catalytic material according to claim 1, characterized in that... In step three, the annealing time at 500℃~600℃ is 1h~2h; the heating rate in step three is 1℃ / min~2℃ / min.

10. The application of a catalytic material prepared by the preparation method according to claim 1, characterized in that... The preparation of the cathode material for lithium-sulfur batteries is carried out according to the following steps: Multi-walled carbon nanotubes, sulfur, and catalytic materials were mixed and ground uniformly at a mass ratio of 2:7:1, and then melted at 150℃~160℃ for 10h~12h to obtain a composite material. The composite material, conductive carbon black, and polyvinylidene fluoride were mixed in N-methylpyrrolidone at a mass ratio of 8:1:1 to obtain a uniform suspension. The uniform suspension was dropped onto carbon cloth and then vacuum dried at 60℃~70℃ for 10h~12h to obtain a lithium-sulfur battery cathode material with a sulfur loading of 1 mg / cm²~5 mg / cm². The total mass ratio of the composite material, conductive carbon black, and polyvinylidene fluoride to N-methylpyrrolidone is 100 mg: 2300 μL.

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