A method for preparing a composite positive electrode of single-atom iron dispersed in a mesoporous carbon host and iodine

Abstract

The present invention relates to a method for preparing a composite cathode material of single-atom iron dispersed in a mesoporous carbon host and iodine. Through a three-step reaction of chemical synthesis, calcination and melt diffusion, a composite cathode material of single-atom iron dispersed in an ordered mesoporous nitrogen-doped carbon host and iodine is successfully synthesized. The single-atom iron catalyst dispersed in the ordered mesoporous nitrogen-doped carbon serves as a "constrained catalytic" host for elemental iodine and can effectively catalyze the conversion of I2 / I ‑ The present invention pioneers a universal host material strategy that combines lightweight, effective physicochemical confinement, and high catalytic activity for the conversion of active materials, significantly promoting the commercial development of aqueous zinc-iodine batteries.

Description

Technical Field

[0001] The invention belongs to the field of battery positive electrode functional materials and relates to a preparation method of a composite positive electrode in which single-atom iron is dispersed in a mesoporous carbon host and iodine. Background Art

[0002] Aqueous zinc-iodine batteries based on elemental iodine / iodide ion conversion are considered promising energy storage devices due to their high theoretical capacity, safety, low cost, wide availability, and environmental friendliness. However, iodine has poor conductivity and the dissolution of polyiodide intermediates causes loss of active materials, resulting in low actual capacity, insufficient reaction kinetics, rapid capacity decay, short life, and corrosion of the metal anode. Selecting a suitable host is of great significance in solving the above problems. Currently, the choice of host is usually the following four types: physical adsorption / heteroatom doping host, chemical adsorption host, metal-organic framework-derived conductive host, and host with introduced electrocatalytic active sites.

[0003] Reference 1 “Hou, Y.; Kong, F.; Wang, Z.; Ren, M.; Qiao, C.; Liu, W.; Yao, J.; Zhang, C.; Zhao, H., High performance rechargeable aqueous zinc-iodine batteries via a double iodine species fixation strategy with mesoporous carbon and modified separator. Journal of Colloid and Interface Science 2023, 629, 279-287” discloses a method for preparing an ordered mesoporous carbon host. A metal organic framework precursor (MOF) was prepared at 1000 °C (5 °C min-1) under the protection of a flowing N2 atmosphere. -1 ) for 2 hours to obtain an ordered mesoporous carbon material, which serves as a host for active iodine in zinc-iodine batteries. The porous structure of the ordered mesoporous carbon host accommodates a large amount of active iodine. However, the physical adsorption capacity of the ordered mesoporous carbon host for the active iodine is insufficient to completely suppress the dissolution of the iodine species. After dissolution, the iodine / polyiodide intermediates shuttle to the negative electrode, resulting in reduced capacity and cycling stability.

[0004] Document 2 “Zeng, X.; Meng, X.; Jiang, W.; Liu, J.; Ling, M.; Yan, L.; Liang, C., Anchoring Polyiodide to Conductive Polymers as Cathode for High-Performance Aqueous Zinc–Iodine Batteries. ACS Sustainable Chemistry & Engineering 2020, 8 (38), 14280-14285” discloses a preparation method using polyaniline (PANI) as an active host. Iodine can be strongly confined in the main chain of polyaniline (PANI) by Coulomb force, and chemical interactions can be used to alleviate iodine sublimation during the preparation process and dissolution of polyiodine intermediates during the circulation process. Moreover, the polymer host is an electrochemically inert material, but the iodine conversion rate, active iodine utilization rate and reaction kinetics are still far from meeting the application requirements, especially under high iodine loading.

[0005] Therefore, we aim to design active iodine / host cathode materials that combine fast conversion kinetics and low shuttling effects. We have published a "constrained catalysis" host strategy. By dispersing single-atom iron catalysts in an ordered mesoporous conductive framework as a single-element iodine host. The porous structure accommodates a large amount of iodine and polyiodide, and the single-atom iron catalyst effectively catalyzes the conversion of iodine / polyiodide, thereby realizing a high-iodine-loaded aqueous zinc-iodine battery with fast reaction kinetics and ultra-long cycle stability. Summary of the Invention

[0006] Technical problems to be solved

[0007] In order to avoid the shortcomings of the existing technology, the present invention proposes a preparation method of single-atom iron dispersed in a mesoporous carbon host and an iodine composite positive electrode, in order to alleviate the problems of easy iodine sublimation and easy dissolution of polyiodide intermediates, which lead to low iodine utilization, low actual capacity, insufficient reaction kinetics, rapid capacity decay, short life and metal negative electrode corrosion, thereby breaking through the application bottleneck of existing zinc-iodine batteries.

[0008] This paper discloses for the first time a method for preparing a composite cathode material composed of single-atom iron dispersed in a mesoporous carbon host and iodine. This method successfully synthesizes a composite cathode material composed of single-atom iron dispersed in an ordered mesoporous nitrogen-doped carbon host and iodine through a three-step reaction process: chemical synthesis, calcination, and melt diffusion.

[0009] Technical Solution

[0010] A method for preparing a composite positive electrode of single-atom iron dispersed in a mesoporous carbon host and iodine, characterized by the following steps:

[0011] Step 1: Preparation of ordered mesoporous UiO-66-NH2 metal organic framework precursor:

[0012] 50 mg of polyether P123 and 25 mg of F127 were dissolved in 3 mL of deionized water, and then 0.4 mL of acetic acid, 150 mg, 1 mmol of sodium perchlorate monohydrate, and 80 μL of toluene were added and stirred to form an emulsion solution;

[0013] 115.6 mg, 0.5 mmol, of zirconium oxynitrate dihydrate and 50 mg, 0.28 mmol, of 2-aminoterephthalic acid were added to the emulsion solution; the mixture was then stirred at 40° C. for 12 hours, washed, and centrifuged to obtain a synthesized sample;

[0014] The synthesized sample was immersed in ethanol at 60 °C for two days. Finally, the product was dried at 60 °C under vacuum overnight to obtain the ordered mesoporous UiO-66-NH2 metal-organic framework precursor MUiO;

[0015] Step 2: Preparation of single-atom iron dispersed in ordered mesoporous nitrogen-doped carbon host:

[0016] 40 mg of ordered mesoporous UiO-66-NH2 metal-organic framework precursor was added to 2 mL of deionized water for dispersion, and the resulting dispersion was ultrasonically treated for 10 minutes; then 0.1 mL of an iron complex solution containing 0.38 M ferrous acetate and 1.14 M 1,10-phenanthroline was added to the ordered mesoporous UiO-66-NH2 metal-organic framework precursor dispersion, and then ultrasonicated for 120 minutes, and finally magnetically stirred for 180 minutes;

[0017] After freeze-drying, the product was ground in a mortar and then heated at 800°C for 1 hour under a nitrogen atmosphere. It was then heated in a tube furnace at 800°C for another 15 minutes for ammonia decomposition. After ammonia decomposition, the product was cooled to room temperature under a nitrogen atmosphere to obtain single-atom iron dispersed in an ordered mesoporous nitrogen-doped carbon host, Fe SAC-MNC.

[0018] Step 3: Preparation of single-atom iron dispersed in ordered mesoporous nitrogen-doped carbon host and iodine composite cathode material:

[0019] Active iodine was infiltrated into the pores of the single-atomic iron dispersed in the ordered mesoporous nitrogen-doped carbon host by the melt diffusion method. 50 mg of the single-atomic iron dispersed in the ordered mesoporous nitrogen-doped carbon host powder and 200 mg of I2 were ground and mixed in a mortar; the mixture was sealed in a hydrothermal autoclave and heated at 120°C for 12 hours, and then heated at 80°C for 12 hours to generate the single-atomic iron dispersed in the ordered mesoporous nitrogen-doped carbon host and iodine composite positive electrode material Fe SAC-MNC / I2.

[0020] The washing and centrifugation are as follows: washing once with water, washing twice with DMF and then centrifuging.

[0021] The samples were immersed in the ethanol for two days, with the ethanol being renewed every day.

[0022] Beneficial effects

[0023] The present invention proposes a method for preparing a composite cathode material of single-atom iron dispersed in a mesoporous carbon host and iodine. Through a three-step reaction of chemical synthesis, calcination and melt diffusion, a composite cathode material of single-atom iron dispersed in an ordered mesoporous nitrogen-doped carbon host and iodine is successfully synthesized. The single-atom iron catalyst dispersed in the ordered mesoporous nitrogen-doped carbon serves as a "constrained catalytic" host for elemental iodine and can effectively catalyze the conversion of I2 / I - The present invention pioneers a universal host material strategy that combines lightweight, effective physicochemical constraints, and high catalytic activity for the conversion of active materials, significantly promoting the commercial development of aqueous zinc-iodine batteries.

[0024] The beneficial effects of the present invention are: the interconnected mesoporous carbon framework host and the conductive channels accommodate a large amount of active iodine, promoting electron / ion transport. In addition, the single-atom iron catalytic site reduces the reaction energy barrier and accelerates the reaction. The conversion of iodine to improve iodine utilization and I - / I2 / I + Redox reaction kinetics. This effectively limits the sublimation of active iodine, the dissolution of polyiodide intermediates, and the catalytic conversion of I2 / I - Redox reactions. This enables high-iodine-loaded Zn||I₂ batteries to exhibit fast reaction kinetics and ultralong cycling stability, resulting in high capacity, high rate performance, and excellent cycling stability. Single-atom iron dispersed in an ordered mesoporous nitrogen-doped carbon host and iodine composite cathode materials bridge the gap between zinc-iodine button batteries and their practical application in commercial devices.

[0025] The beneficial effects expressed by the accompanying drawings of the embodiments are as follows:

[0026] Figure 1 This is a transmission electron microscopy (TEM) image of single-atom iron dispersed in an ordered mesoporous nitrogen-doped carbon host (Fe SAC-MNC), prepared in Example 1 of the present invention. The TEM image shows uniformly distributed nanospheres with a diameter of approximately 80 nm, abundantly distributed within the ordered mesopores. This demonstrates the successful synthesis of a nitrogen-doped carbon material with an ordered mesoporous nanosphere morphology.

[0027] Figure 2This is a high-resolution spherical aberration-corrected electron microscopy (HAADF-STEM) image of single-atom iron dispersed in an ordered mesoporous nitrogen-doped carbon host (Fe SAC-MNC), prepared in Example 1 of the present invention. The HAADF-STEM image shows bright spots distributed across the nanospheres, indicating the presence of a large number of single-atom iron atoms. This demonstrates the successful synthesis of single-atom iron atoms on ordered mesoporous nitrogen-doped carbon.

[0028] Figure 3 Curves 1, 2, 3, 4, and 5 are the X-ray diffraction (XRD) patterns of the ordered mesoporous UiO-66-NH2 metal organic framework precursor (MUiO) prepared in Example 1 of the present invention, the ordered mesoporous nitrogen-doped carbon host (MNC) prepared in Example 2, the single-atom iron dispersed in the ordered mesoporous nitrogen-doped carbon host (Fe SAC-MNC) prepared in Example 1, the single-atom iron dispersed in the ordered mesoporous nitrogen-doped carbon host and iodine composite positive electrode material (Fe SAC-MNC / I2) prepared in Example 1, and powdered iodine (I2), respectively. The ordered mesoporous nitrogen-doped carbon host (MNC) and the single-atom iron dispersed in the ordered mesoporous nitrogen-doped carbon host (Fe SAC-MNC) exhibit two broad peaks in the 2θ range, which are 24° and 44°, respectively, corresponding to the (002) and (101) diffraction peaks of graphite carbon. Moreover, the XRD peaks of the single-atom iron dispersed in the ordered mesoporous nitrogen-doped carbon host and iodine composite positive electrode material (Fe SAC-MNC / I2) are consistent with those of powdered iodine, indicating that iodine has been successfully introduced into the single-atom iron dispersed in the ordered mesoporous nitrogen-doped carbon host.

[0029] Figure 4 Curves 6 and 7 are the pore size distribution curves of the single-atom iron dispersed in an ordered mesoporous nitrogen-doped carbon host (Fe SAC-MNC) and the single-atom iron dispersed in an ordered mesoporous nitrogen-doped carbon host and iodine composite cathode material (FeSAC-MNC / I2), respectively, prepared in Example 1 of the present invention. After the introduction of iodine, the number of mesopores in the single-atom iron dispersed in the ordered mesoporous nitrogen-doped carbon host (FeSAC-MNC) suddenly decreases, indicating that the present invention successfully introduces iodine into the mesopores of the single-atom iron dispersed in the ordered mesoporous nitrogen-doped carbon host (Fe SAC-MNC), which is beneficial to suppressing the sublimation of iodine and the dissolution of polyiodide intermediates.

[0030] Figure 5 Curves 8, 9, and 10 are the activation energy values obtained from the iodine reduction reaction (IRR) of the single-atom iron dispersed in the ordered mesoporous nitrogen-doped carbon host (Fe SAC-MNC) prepared in Example 1 of the present invention, the ordered mesoporous nitrogen-doped carbon host (MNC) prepared in Example 2, and Ketjen black (KB) powder in a two-electrode system. The E of the iodine reduction reaction (IRR) of the single-atom iron dispersed in the ordered mesoporous nitrogen-doped carbon host (Fe SAC-MNC) was calculated using the Arrhenius equation.a 27.878 kJ·mol -1 , less than MNC (31.386KJ·mol -1 ) and (39.654 kJ·mol -1 ), indicating that Fe SAC-MNC has ultrafast reaction kinetics.

[0031] Figure 6 Curves 11, 12, and 13 are the rate performance graphs of aqueous zinc-iodine button cells coated on carbon cloth and assembled with single-atom iron dispersed in ordered mesoporous nitrogen-doped carbon host and iodine composite cathode material (Fe SAC-MNC / I2) prepared in Example 1, ordered mesoporous nitrogen-doped carbon host and iodine composite cathode material (Fe SAC-MNC / I2) prepared in Example 2, and Ketjen black host and iodine composite cathode material (KB / I2) prepared in Example 3. Single-atom iron dispersed in ordered mesoporous nitrogen-doped carbon host and iodine composite cathode material zinc battery (Zn||Fe SAC-MNC / I2) at 0.3, 0.5, 1, 1, 3, 5, and 15 A g -1 The results were 188.21, 180.92, 175.96, 168.53, 163.32, 151.33 and 139.60 mAh g -1 The superior specific capacity is almost double and triple that of ordered mesoporous nitrogen-doped carbon host and iodine composite cathode material zinc battery (Zn||MNC / I2) and Ketjen black host and iodine composite cathode material (Zn||KB / I2). More notably, the Fe SAC-MNC / I2 cathode has a high specific capacity of 15A g -1 Achieved 139.60mAh g -1 High capacity and stable Coulombic efficiency of 99.88%.

[0032] Figure 7 Curves 14, 15, and 16 are the long-cycle performance graphs of aqueous zinc-iodine button batteries coated on carbon cloth and assembled with single-atom iron dispersed in ordered mesoporous nitrogen-doped carbon host and iodine composite cathode material (Fe SAC-MNC / I2) prepared in Example 1, ordered mesoporous nitrogen-doped carbon host and iodine composite cathode material (Fe SAC-MNC / I2) prepared in Example 2, and Ketjen black host and iodine composite cathode material (KB / I2) prepared in Example 3. -1 The high current density showed ultra-stable cycle performance and ultra-long service life, with an initial capacity retention rate of 80.5% (from 198.5 to 159.7 mAh g -1), even more than 50,000 cycles. Although the ordered mesoporous nitrogen-doped carbon host and iodine composite cathode material zinc battery (Zn||MNC / I2) showed more stable cycling performance than the Ketjen black host and iodine composite cathode material (KB / I2), its capacity was limited (68.49 to 46.26 mAh g -1 ) and a very short lifespan (only 7000 cycles). The above results illustrate the excellent electrocatalytic ability of the single-atom iron in the present invention and the strong iodine adsorption ability of the ordered mesoporous nitrogen-doped carbon material as an I2 host. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a transmission electron microscope (TEM) image of single-atom iron dispersed in an ordered mesoporous nitrogen-doped carbon host (Fe SAC-MNC) prepared in Example 1 of the present invention.

[0034] Figure 2 This is a high-resolution spherical aberration-corrected electron microscopy (HAADF-STEM) image of single-atom iron dispersed in an ordered mesoporous nitrogen-doped carbon host (Fe SAC-MNC) prepared in Example 1 of the present invention.

[0035] Figure 3 Curve 1, curve 2, curve 3, curve 4 and curve 5 are the X-ray diffraction (XRD) patterns of the ordered mesoporous UiO-66-NH2 metal organic framework precursor (MUiO) prepared in Example 1 of the present invention, the ordered mesoporous nitrogen-doped carbon host (MNC) prepared in Example 2, the single atomic iron dispersed in the ordered mesoporous nitrogen-doped carbon host (Fe SAC-MNC) prepared in Example 1, the single atomic iron dispersed in the ordered mesoporous nitrogen-doped carbon host and iodine composite positive electrode material (Fe SAC-MNC / I2) prepared in Example 1 and powdered iodine (I2), respectively.

[0036] Figure 4 Curve 6 and curve 7 are the pore size distribution curves of single-atom iron dispersed in ordered mesoporous nitrogen-doped carbon host (Fe SAC-MNC) and single-atom iron dispersed in ordered mesoporous nitrogen-doped carbon host and iodine composite positive electrode material (FeSAC-MNC / I2) prepared in Example 1 of the present invention, respectively.

[0037] Figure 5 Curves 8, 9, and 10 are the activation energy values (E) obtained by the iodine reduction reaction (IRR) of the single-atom iron dispersed in the ordered mesoporous nitrogen-doped carbon host (Fe SAC-MNC) prepared in Example 1 of the present invention, the ordered mesoporous nitrogen-doped carbon host (MNC) prepared in Example 2, and Ketjen black (KB) powder in the two-electrode system. a ).

[0038] Figure 6Curves 11, 12, and 13 are rate performance diagrams of the single-atom iron dispersed in the ordered mesoporous nitrogen-doped carbon host and iodine composite positive electrode material (Fe SAC-MNC / I2) prepared in Example 1 of the present invention, the ordered mesoporous nitrogen-doped carbon host and iodine composite positive electrode material (Fe SAC-MNC / I2) prepared in Example 2, and the Ketjen black host and iodine composite positive electrode material (KB / I2) prepared in Example 3, which are coated on carbon cloth and assembled into aqueous zinc-iodine button batteries.

[0039] Figure 7 Curves 14, 15, and 16 are respectively the long cycle performance graphs of the single-atom iron dispersed in the ordered mesoporous nitrogen-doped carbon host and iodine composite positive electrode material (Fe SAC-MNC / I2) prepared in Example 1 of the present invention, the ordered mesoporous nitrogen-doped carbon host and iodine composite positive electrode material (Fe SAC-MNC / I2) prepared in Example 2, and the Ketjen black host and iodine composite positive electrode material (KB / I2) prepared in Example 3, which are coated on carbon cloth and assembled into aqueous zinc-iodine button batteries. DETAILED DESCRIPTION

[0040] The present invention will now be further described with reference to the embodiments and accompanying drawings:

[0041] The following examples refer to Figure 1-7

[0042] Example 1:

[0043] (1) Preparation of ordered mesoporous UiO-66-NH2 metal-organic framework precursor. 50 mg of polyether P123 and 25 mg of F127 were dissolved in 3 mL of deionized water, and then 0.4 mL of acetic acid, 150 mg, 1 mmol of sodium perchlorate monohydrate and 80 μL of toluene were added and stirred to form an emulsion solution. Subsequently, 115.6 mg, 0.5 mmol of zirconium oxynitrate dihydrate and 50 mg, 0.28 mmol of 2-aminoterephthalic acid were added to the above mixture. Then, the mixture was stirred at 40 ° C for 12 hours. Washed once with water, washed twice with DMF, and centrifuged to obtain a sample. The synthesized sample was soaked in ethanol at 60 ° C for two days, and the ethanol was renewed every day. Finally, the product was dried at 60 ° C under vacuum overnight to obtain an ordered mesoporous UiO-66-NH2 metal-organic framework precursor (MUiO).

[0044] (2) Preparation of single-atom iron dispersed in an ordered mesoporous nitrogen-doped carbon host. 40 mg of ordered mesoporous UiO-66-NH2 metal-organic framework precursor was added to 2 mL of deionized water, and the resulting dispersion was ultrasonically treated for 10 minutes. Then, 0.1 mL of an iron complex solution containing 0.38 M ferrous acetate and 1.14 M 1,10-phenanthroline was added to the ordered mesoporous UiO-66-NH2 metal-organic framework precursor dispersion, followed by ultrasonic treatment for another 120 minutes and finally magnetic stirring for 180 minutes. After freeze-drying, the synthesized sample was ground in a mortar and then heated at 800 ° C for 1 hour under a nitrogen atmosphere. It was then heated in a tube furnace with ammonia at 800 ° C for another 15 minutes. After ammonia decomposition, the sample was cooled to room temperature under N2 atmosphere to obtain single-atom iron dispersed in an ordered mesoporous nitrogen-doped carbon host (Fe SAC-MNC).

[0045] (3) Preparation of single-atom iron dispersed in ordered mesoporous nitrogen-doped carbon host and iodine composite cathode material. Active iodine was infiltrated into the pores of single-atom iron dispersed in ordered mesoporous nitrogen-doped carbon host by melt diffusion method. 50 mg of single-atom iron dispersed in ordered mesoporous nitrogen-doped carbon host powder was ground and mixed with 200 mg of I2 in a mortar. The mixture was sealed in a hydrothermal autoclave and heated at 120 ° C for 12 hours, and then heated at 80 ° C for 12 hours to generate single-atom iron dispersed in ordered mesoporous nitrogen-doped carbon host and iodine composite cathode material (Fe SAC-MNC / I2).

[0046] Example 2:

[0047] (1) Preparation of ordered mesoporous UiO-66-NH2 metal-organic framework precursor. 50 mg of polyether P123 and 25 mg of F127 were dissolved in 3 mL of deionized water, and then 0.4 mL of acetic acid, 150 mg, 1 mmol of sodium perchlorate monohydrate and 80 μL of toluene were added and stirred to form an emulsion solution. Subsequently, 115.6 mg, 0.5 mmol of zirconium oxynitrate dihydrate and 50 mg, 0.28 mmol of 2-aminoterephthalic acid were added to the above mixture. Then, the mixture was stirred at 40 ° C for 12 hours. Washed once with water, washed twice with DMF, and centrifuged to obtain a sample. The synthesized sample was soaked in ethanol at 60 ° C for two days, and the ethanol was renewed every day. Finally, the product was dried at 60 ° C under vacuum overnight to obtain an ordered mesoporous UiO-66-NH2 metal-organic framework precursor (MUiO).

[0048] (2) Preparation of ordered mesoporous nitrogen-doped carbon host. 40 mg of ordered mesoporous UiO-66-NH2 metal organic framework precursor was added to 2 mL of deionized water, and the resulting dispersion was ultrasonically treated for 120 minutes and finally magnetically stirred for 180 minutes. After freeze-drying, the synthesized sample was ground in a mortar and then heated at 800 ° C for 1 hour under a nitrogen atmosphere. It was then heated for another 15 minutes in a tube furnace with ammonia at 800 ° C. After ammonia decomposition, the sample was cooled to room temperature under N2 atmosphere to obtain an ordered mesoporous nitrogen-doped carbon host (MNC).

[0049] (3) Preparation of ordered mesoporous nitrogen-doped carbon host and iodine composite cathode material. Active iodine was infiltrated into the pores of the ordered mesoporous nitrogen-doped carbon host by the melt diffusion method. 50 mg of ordered mesoporous nitrogen-doped carbon host powder was ground and mixed with 200 mg of I2 in a mortar. The mixture was sealed in a hydrothermal autoclave and heated at 120°C for 12 hours, and then heated at 80°C for 12 hours to generate an ordered mesoporous nitrogen-doped carbon host and iodine composite cathode material (MNC / I2).

[0050] Example 3:

[0051] Preparation of a Ketjen black host and iodine composite cathode material. Using the melt diffusion method, 50 mg of Ketjen black powder and 200 mg of I2 were ground and mixed in a mortar. The mixture was sealed in a hydrothermal autoclave and heated at 120°C for 12 hours, followed by heating at 80°C for 12 hours, to produce the Ketjen black host and iodine composite cathode material (KB / I2).

[0052] Figure 1 This is a transmission electron microscopy (TEM) image of single-atom iron dispersed in an ordered mesoporous nitrogen-doped carbon host (Fe SAC-MNC), prepared in Example 1 of the present invention. The TEM image shows uniform nanospheres with a diameter of ~80 nm and abundant ordered mesopores. This ordered mesoporous structure helps suppress the volatilization of active iodine and the dissolution of polyiodide intermediates, thereby improving the iodine utilization rate of aqueous zinc-iodine batteries.

[0053] Figure 2 This is a high-resolution aberration-corrected electron microscopy (HAADF-STEM) image of single iron atoms dispersed in an ordered mesoporous nitrogen-doped carbon host (Fe SAC-MNC), prepared in Example 1 of the present invention. The bright spots circled in red in the image represent single iron atoms. This demonstrates the successful synthesis of single iron atoms in an ordered mesoporous nitrogen-doped carbon host.

[0054] Figure 3Curves 1, 2, 3, 4, and 5 are the X-ray diffraction (XRD) patterns of the ordered mesoporous UiO-66-NH2 metal-organic framework precursor (MUiO) prepared in Example 1 of the present invention, the ordered mesoporous nitrogen-doped carbon host (MNC) prepared in Example 2, the single-atom iron dispersed in the ordered mesoporous nitrogen-doped carbon host (Fe SAC-MNC) prepared in Example 1, the single-atom iron dispersed in the ordered mesoporous nitrogen-doped carbon host and iodine composite cathode material (Fe SAC-MNC / I2) prepared in Example 1, and powdered iodine (I2), respectively. After calcination, MNC and Fe SAC-MNC exhibit two broad peaks in the 2θ range, at 24° and 44°, respectively, corresponding to the (002) and (101) diffraction peaks of graphitized carbon. In addition, the diffraction peak of I2 was detected after the Fe SAC-MNC was composited with I2, indicating that we have successfully introduced active iodine into the ordered mesoporous nitrogen-doped carbon host through the melt diffusion method.

[0055] Figure 4 Curves 6 and 7 show the pore size distribution curves for the single-atom iron dispersed in an ordered mesoporous nitrogen-doped carbon host (Fe SAC-MNC) and the single-atom iron dispersed in an ordered mesoporous nitrogen-doped carbon host and iodine composite cathode material (FeSAC-MNC / I2), respectively, prepared in Example 1 of the present invention. With the introduction of I2 molecules, the pore content decreases significantly, indicating that the active iodine is successfully confined within the host's mesopores.

[0056] Figure 5 Curves 8, 9, and 10 are the activation energy values (E) obtained by the iodine reduction reaction (IRR) of the single-atom iron dispersed in the ordered mesoporous nitrogen-doped carbon host (Fe SAC-MNC) prepared in Example 1 of the present invention, the ordered mesoporous nitrogen-doped carbon host (MNC) prepared in Example 2, and Ketjen black (KB) powder in the two-electrode system. a The activation energy of the IRR of Fe SAC-MNC was calculated to be 27.878 kJ·mol -1 , less than MNC (31.386KJ·mol -1 ) and (39.654 kJ·mol -1 ). This indicates that under the catalysis of single-atom iron, the IRR reaction achieves ultrafast reaction kinetics.

[0057] Figure 6Curves 11, 12, and 13 are the rate performance diagrams of aqueous zinc-iodine button cells coated on carbon cloth and assembled with single-atom iron dispersed in an ordered mesoporous nitrogen-doped carbon host and iodine composite cathode material (Fe SAC-MNC / I2) prepared in Example 1, the ordered mesoporous nitrogen-doped carbon host and iodine composite cathode material (Fe SAC-MNC / I2) prepared in Example 2, and the Ketjen black host and iodine composite cathode material (KB / I2) prepared in Example 3. The Zn||Fe SAC-MNC / I2 battery was tested at current densities of 0.3, 0.5, 1, 1, 3, 5, and 15 A g -1 The results were 188.21, 180.92, 175.96, 168.53, 163.32, 151.33 and 139.60 mAh g -1 The high capacity is almost double and triple that of Zn||MNC / I2 and Zn||KB / I2 batteries, respectively. This demonstrates the excellent catalytic and confinement effects of the host, which combines single-atom iron catalysis and ordered mesoporous nitrogen-doped carbon, on active iodine.

[0058] Figure 7 Curves 14, 15, and 16 are respectively the long cycle performance graphs of aqueous zinc-iodine button batteries coated on carbon cloth and assembled with single-atom iron dispersed in ordered mesoporous nitrogen-doped carbon host and iodine composite cathode material (Fe SAC-MNC / I2) prepared in Example 1 of the present invention, ordered mesoporous nitrogen-doped carbon host and iodine composite cathode material (Fe SAC-MNC / I2) prepared in Example 2, and Ketjen black host and iodine composite cathode material (KB / I2) prepared in Example 3. -1 The high current density showed ultra-stable cycle performance and ultra-long service life, with an initial capacity retention rate of 80.5% (from 198.5 to 159.7 mAh g -1 ), achieving more than 50,000 cycles. Single-atom iron dispersed in an ordered mesoporous nitrogen-doped carbon host achieves high iodine utilization, fast redox reaction kinetics, long cycle life, and no shuttle effect in Zn||I2 batteries. The interconnected mesoporous carbon framework promotes electron / ion transport. The single-atom iron catalytic sites still effectively improve iodine utilization and I under high iodine loading. - / I2 / I + The redox reaction kinetics achieve high iodine utilization, fast redox reaction kinetics, long cycle life, and no shuttle effect in Zn||I2 batteries.

Claims

1. A method for preparing a composite positive electrode of single-atom iron dispersed in a mesoporous carbon host and iodine, characterized in that Here are the steps: Step 1: Preparation of ordered mesoporous UiO-66-NH2 metal organic framework precursor: 50 mg of polyether P123 and 25 mg of F127 were dissolved in 3 mL of deionized water, and then 0.4 mL of acetic acid, 150 mg, 1 mmol of sodium perchlorate monohydrate, and 80 μL of toluene were added and stirred to form an emulsion solution; 115.6 mg, 0.5 mmol, of zirconium oxynitrate dihydrate and 50 mg, 0.28 mmol, of 2-aminoterephthalic acid were added to the emulsion solution; the mixture was then stirred at 40° C. for 12 hours, washed, and centrifuged to obtain a synthesized sample; The synthesized sample was immersed in ethanol at 60 °C for two days. Finally, the product was dried at 60 °C under vacuum overnight to obtain the ordered mesoporous UiO-66-NH2 metal-organic framework precursor MUiO; Step 2: Preparation of single-atom iron dispersed in ordered mesoporous nitrogen-doped carbon host: 40 mg of ordered mesoporous UiO-66-NH2 metal-organic framework precursor was added to 2 mL of deionized water for dispersion, and the resulting dispersion was ultrasonically treated for 10 minutes; then 0.1 mL of an iron complex solution containing 0.38 M ferrous acetate and 1.14 M 1,10-phenanthroline was added to the ordered mesoporous UiO-66-NH2 metal-organic framework precursor dispersion, and then ultrasonicated for 120 minutes, and finally magnetically stirred for 180 minutes; After freeze-drying, the product was ground in a mortar and then heated at 800°C for 1 hour under a nitrogen atmosphere; subsequently, it was heated in a tube furnace at 800°C for another 15 minutes for aminolysis; After ammonia decomposition, the mixture was cooled to room temperature under N2 atmosphere to obtain single-atom iron dispersed in an ordered mesoporous nitrogen-doped carbon host Fe SAC-MNC. Step 3: Preparation of single-atom iron dispersed in ordered mesoporous nitrogen-doped carbon host and iodine composite cathode material: Active iodine was infiltrated into the pores of the single-atomic iron dispersed in the ordered mesoporous nitrogen-doped carbon host by the melt diffusion method. 50 mg of the single-atomic iron dispersed in the ordered mesoporous nitrogen-doped carbon host powder and 200 mg of I2 were ground and mixed in a mortar; the mixture was sealed in a hydrothermal autoclave and heated at 120°C for 12 hours, and then heated at 80°C for 12 hours to generate the single-atomic iron dispersed in the ordered mesoporous nitrogen-doped carbon host and iodine composite positive electrode material Fe SAC-MNC / I2.

2. The method for preparing a composite positive electrode of single-atom iron dispersed in a mesoporous carbon host and iodine according to claim 1, characterized in that: The washing and centrifugation are as follows: washing once with water, washing twice with DMF and then centrifuging.

3. The method for preparing a composite positive electrode of single-atom iron dispersed in a mesoporous carbon host and iodine according to claim 1, characterized in that: The samples were immersed in the ethanol for two days, with the ethanol being renewed every day.

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