Starch integrated catalyst / linear sulfur integrated aqueous zinc-sulfur battery positive electrode material and preparation method thereof

Abstract

The invention provides a starch integrated catalyst / linear sulfur integrated aqueous zinc-sulfur battery positive electrode material and a preparation method thereof.The method comprises the steps that starch, sulfur and ketjen black are weighed and mixed to be uniform, and a mixture is obtained; calcining the mixture under a vacuum condition to prepare a starch / sulfur / ketjen black composite material; and finally, soaking the obtained composite material in a polyiodide aqueous solution until the supernate becomes colorless, centrifuging and drying to obtain the starch integrated catalyst / linear sulfur integrated aqueous zinc-sulfur battery positive electrode material. The iodine is fixed in a starch double helix structure through hydrogen bond interaction between iodine and a starch polyhydroxy structure on the basis of a chromogenic reaction of starch and iodine, the shuttle effect of polyiodide is inhibited, the iodine catalyst is effectively enriched on the positive electrode side, and the catalytic oxidation capacity of the iodine catalyst is maximized. The prepared positive electrode material has the advantages of high specific energy, high magnification and high stability, and can meet the application requirements of the future energy storage market.

Description

Technical Field

[0001] This invention relates to the field of secondary battery electrode materials technology, and in particular, to a starch-integrated catalyst / linear sulfur integrated aqueous zinc-sulfur battery cathode material and its preparation method. Background Technology

[0002] Aqueous sulfur-based batteries are known for their high safety and high theoretical specific capacity (1675 mAh g). - ¹) and low cost (52 Ah $) - ¹) and other advantages have led to its widespread recognition as an ideal candidate for large-scale energy storage devices. Among them, aqueous zinc-sulfur batteries (AZSBs) have attracted widespread attention from researchers because they use zinc metal as the negative electrode, which is stable in air and has a redox potential (-0.76 V vs. SHE) compatible with aqueous electrolytes. Unlike the solid-liquid-solid conversion pathway in alkali metal-sulfur batteries, AZSBs adopt a solid-solid conversion mechanism, which can effectively avoid the dissolution of active materials caused by polysulfide shuttle, providing a more stable reaction pathway for the sulfur positive electrode in aqueous electrolytes. However, in actual tests, sulfur positive electrodes based on the solid-solid conversion pathway often exhibit poor reversibility, mainly due to two reasons: first, the high oxidation energy barrier of zinc sulfide (ZnS); and second, the insulating properties and strong bond energies of the cyclic S8 molecule, resulting in its weak electroreduction activity.

[0003] Currently, introducing trace amounts of iodine-based catalysts into the electrolyte is widely considered an effective strategy to lower the high oxidation energy barrier of ZnS. This is because polyiodides (I3) possess oxidizing properties. - The high-energy-barrier electrochemical oxidation pathway of ZnS (ZnS→S+Zn) can be used to oxidize ZnS. 2+ +2e - The conversion to a low-energy-barrier chemical oxidation pathway (ZnS + I3) is achieved. - →Zn 2+ +S+3I - However, the regular I3 -Oxidizing media often exhibit limited oxidizing capacity for ZnS, making it difficult to achieve a complete chemical oxidation pathway for ZnS. Furthermore, the polyiodides generated in the electrolyte inevitably trigger a "shuttle effect," accelerating catalyst consumption at the negative electrode. Therefore, enhancing the oxidizing capacity of iodine catalysts and eliminating their "shuttle effect" has become the primary challenge in maximizing the effectiveness of iodine-based catalysts in lowering the ZnS oxidation energy barrier. To improve the electroreduction activity of cyclic S8 molecules, researchers have designed various strategies, such as carbon host and chalcogenide doping, to enhance conductivity and interfacial contact, thereby increasing the electroreduction activity of sulfur. Although physical contact does improve electron / ion transport pathways and effectively solves the insulation problem of sulfur, it should be noted that the above strategies still have limited effect on promoting the reduction process of cyclic S8 molecules. The fundamental reason is that the strong bond energy within the cyclic S8 molecule makes it difficult for the SS bonds to dissociate. Compared to nonpolar cyclic S8 molecules, polar linear sulfur molecules possess longer SS bonds, which weaken the bonding forces between sulfur atoms and enhance the polar interaction between sulfur and metal cations. Therefore, linear sulfur often exhibits higher reactivity than cyclic S8 molecules. However, free chain sulfur molecules are thermodynamically unstable and typically require linkage with a polymer backbone or a microporous carbon matrix to provide size-matched physical confinement space. This limits material selection and leads to problems such as low active material loading (<30%). More notably, reported linear sulfur cathodes generally exhibit large polarization (0.75 V), keeping their energy density relatively low.

[0004] In summary, optimizing the oxidation or reduction process alone is insufficient to fully realize the application potential of sulfur cathodes. Therefore, simultaneously enhancing the catalytic oxidation capacity of iodine-based catalysts and the electroreduction activity of sulfur is key to improving sulfur redox kinetics. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a starch-integrated catalyst / linear sulfur integrated aqueous zinc-sulfur battery cathode material and its preparation method, aiming to simultaneously improve the catalytic oxidation ability of iodine catalysts and the electroreduction activity of sulfur to reduce the redox energy barrier of sulfur and improve sulfur conversion kinetics.

[0006] To achieve the above objectives, the present invention provides a method for preparing a starch-integrated catalyst / linear sulfur integrated aqueous zinc-sulfur battery cathode material, comprising the following steps: Step 1: Weigh a certain amount of starch, sulfur, and Ketjen black and mix them evenly to obtain a mixture of starch, sulfur, and Ketjen black. Step 2: The mixture of starch, sulfur and Ketjenblack is calcined in a vacuum environment to obtain a starch / sulfur / Ketjenblack composite material. Step 3: Immerse the starch / sulfur / Ketjen black composite material in a polyiodide aqueous solution until the supernatant is colorless. After centrifugation and drying, the starch-integrated catalyst / linear sulfur integrated aqueous zinc-sulfur battery cathode material is obtained.

[0007] Furthermore, in step one, the mass ratio of sulfur, starch, and Ketjen black is 12:1.5-4.5:8.5-5.5.

[0008] Furthermore, in step one, the starch used is amylopectin. Its starch source can be any one of corn, potato, or rice.

[0009] Furthermore, in step one, the mixing method used is ball milling.

[0010] Furthermore, in step one, the ball milling speed during the ball milling mixing process is 100rpm-300rpm.

[0011] Furthermore, in step two, the mixture of starch, sulfur, and Ketjen black is placed in a vacuum quartz glass tube for calcination.

[0012] Furthermore, in step two, the calcination temperature is 145℃-195℃, the heating rate is 2℃ / min-10℃ / min, and the calcination time is 6h-24h.

[0013] Furthermore, in step three, I2 and KI are dissolved in 100 mL of ultrapure water at a 1:1 molar ratio to prepare a polyiodide aqueous solution; wherein the molar concentration of I2 and KI is 1 mmol / L.

[0014] Furthermore, in step three, the drying temperature is 30℃-50℃.

[0015] The present invention also provides a starch-integrated catalyst / linear sulfur integrated aqueous zinc-sulfur battery cathode material, which is prepared by the above-described preparation method.

[0016] The present invention has the following beneficial effects: 1. This invention provides a method for preparing a starch-integrated catalyst / linear sulfur-integrated aqueous zinc-sulfur battery cathode material. This method is based on the colorimetric reaction between starch and iodine. Iodine is fixed within the starch double-helix structure through hydrogen bonding between iodine and the polyhydroxyl structure of starch, suppressing the shuttle effect of polyiodides, effectively enriching the iodine catalyst on the cathode side and maximizing its catalytic oxidation capacity. Simultaneously, it activates the highly oxidizing I5. The catalyst enhances the chemical oxidation of the discharge product ZnS, effectively reduces the oxidation energy barrier of ZnS, and improves the reversibility of the S cathode.

[0017] 2. This invention provides a method for preparing a starch-integrated catalyst / linear sulfur integrated aqueous zinc-sulfur battery cathode material. This method is based on the bonding of nucleophilic sulfur chains with electrophilic C1 sites in the starch backbone via CS bonds, transforming electrochemically inert cyclic sulfur into highly electrochemically active chain sulfur. The starch-stabilized chain sulfur possesses longer SS bond lengths and stronger polarity, effectively reducing the SS bond dissociation energy and enhancing the interaction between S and Zn. 2+ The polar interaction between them significantly reduces the reduction energy barrier of sulfur and improves the reduction reaction kinetics of sulfur cathode.

[0018] 3. Based on the dual enhancement of sulfur redox kinetics, the cathode material prepared by the method of this invention has high specific energy (calculated based on the mass of the active material sulfur, 1120 Wh kg). 1 High magnification (5 Ag) 1 It still maintains 829 mAh g at current density 1 ) and high stability (5 Ag) 1 With its advantage of maintaining nearly 100% capacity after 1300 cycles at current density, it can meet the application needs of the future energy storage market.

[0019] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the figures. Attached Figure Description

[0020] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 These are XRD comparison images of the cathode materials prepared using Example 1, Comparative Example 1, Comparative Example 3, and Comparative Example 6 of the present invention. Figure 2 The above are Raman comparison diagrams of the cathode materials prepared using Example 1, Comparative Example 1, Comparative Example 3 and Comparative Example 6 of the present invention. Figure 3 The material and starch were prepared using the method described in Comparative Example 6 of this invention. 13 Comparison of C NMR spectra; Figure 4 The aqueous zinc-sulfur battery assembled using the positive electrode materials prepared in Example 1 and Comparative Example 1 of this invention is tested at 0.1 A g. 1 Comparison of charge and discharge curves; Figure 5 The aqueous zinc-sulfur battery assembled using the cathode materials prepared in Comparative Examples 2 and 3 of this invention, at a speed of 0.1 A g... 1 Comparison of charge and discharge curves; Figure 6 Figure a is a comparison diagram of the material prepared using Comparative Example 6 of the present invention and the average SS bond length within the cyclic S8 molecule; Figure 6 b is the material prepared using Comparative Example 6 of this invention, and the cyclic S8 molecule and Zn. 2+ Adsorption energy comparison chart; Figure 6 Figure c is a comparison diagram of the activation energies of the material prepared using Comparative Example 6 of this invention and the cyclic S8 molecule; Figure 7 The aqueous zinc-sulfur battery assembled using the cathode materials prepared in Comparative Examples 4 and 5 of this invention, at a speed of 0.1 A g... 1 Comparison of charge and discharge curves; Figure 8 In the middle, a is a mixture of zinc sulfide, iodine / starch, and I3. Comparison of UV spectra of supernatant after solution treatment; Figure 8 In section b, zinc sulfide is mixed with iodine / starch and I3. XRD comparison of the products after solution treatment; Figure 8 c is a mixture of zinc sulfide, iodine / starch, and I3. Raman comparison of the products after solution treatment; Figure 9 This is a comparison chart of the rate performance of aqueous zinc-sulfur batteries assembled using the cathode materials prepared in Example 1 and Comparative Examples 1-3 of this invention at different current densities. Figure 10 Figures a and b are in-situ ultraviolet spectra comparisons of aqueous zinc-sulfur batteries assembled using the cathode material prepared in Comparative Example 1 of this invention during the charging and discharging process. Figure 10 c and d are in-situ ultraviolet spectra comparison diagrams of aqueous zinc-sulfur batteries assembled using the cathode material prepared by Comparative Example 2 of the present invention during the charging and discharging process. Figure 10 Figures e and f are in-situ ultraviolet spectra comparisons of aqueous zinc-sulfur batteries assembled using the cathode material prepared in Comparative Example 3 of this invention during the charging and discharging process. Figure 10 In the figure, g and h are in-situ ultraviolet spectra comparison diagrams of aqueous zinc-sulfur batteries assembled using the cathode material prepared in Example 1 of this invention during the charging and discharging process. Figure 11 Aqueous zinc-sulfur batteries assembled using the cathode materials prepared in Example 1 and Comparative Examples 1-3 of this invention, at 5 A g 1The following is a comparison chart of long-cycle performance. Detailed Implementation

[0021] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways as defined and covered by the claims.

[0022] Example 1: A method for preparing a starch-integrated catalyst / linear sulfur integrated aqueous zinc-sulfur battery cathode material includes the following steps: Step 1: Commercial sulfur powder, corn amylopectin and Ketjen black are ball-milled and mixed evenly at a mass ratio of 12:3:7 at a ball mill speed of 300 rpm to obtain a mixture of sulfur powder, corn amylopectin and Ketjen black in a mass ratio of 12:3:7. Step 2: The mixture of sulfur powder, corn amylopectin and Ketjen black in a 12:3:7 ratio is placed in a vacuum glass tube and calcined at 155°C for 12 hours at a heating rate of 5°C / min to obtain a starch / sulfur / Ketjen black composite material in a 12:3:7 ratio. Step 3: Immerse the 12:3:7 starch / sulfur / Ketjenblack composite material in 100 mL of 1 mmol / L KI and 1 mmol / L I2 aqueous solution until the supernatant is colorless. Centrifuge and dry at 40°C to obtain iodine / starch / sulfur / Ketjenblack, which is the starch-integrated catalyst / sulfur integrated cathode material.

[0023] Example 2: A method for preparing a starch-integrated catalyst / linear sulfur integrated aqueous zinc-sulfur battery cathode material includes the following steps: Step 1: Commercial sulfur powder, corn amylopectin and Ketjen black are ball-milled and mixed evenly at a mass ratio of 12:1.5:8.5 at a ball mill speed of 300 rpm to obtain a mixture of sulfur powder, corn amylopectin and Ketjen black in a mass ratio of 12:1.5:8.5. Step 2: The mixture of sulfur powder, corn amylopectin and Ketjen black in a ratio of 12:1.5:8.5 is placed in a vacuum glass tube and calcined at 155°C for 12 hours at a heating rate of 5°C / min to obtain a starch / sulfur / Ketjen black composite material in a ratio of 12:1.5:8.5. Step 3: Immerse the 12:1.5:8.5 starch / sulfur / Ketjenblack composite material in 100 mL of 1 mmol / L KI and 1 mmol / L I2 aqueous solution until the supernatant is colorless. Centrifuge and dry at 40°C to obtain iodine / starch / sulfur / Ketjenblack, which is the starch-integrated catalyst / sulfur integrated cathode material.

[0024] Example 3: A method for preparing a starch-integrated catalyst / linear sulfur integrated aqueous zinc-sulfur battery cathode material includes the following steps: Step 1: Commercial sulfur powder, corn amylopectin, and Ketjen black are ball-milled and mixed evenly at a mass ratio of 12:4.5:5.5 at a ball mill speed of 300 rpm to obtain a mixture of sulfur powder, corn amylopectin, and Ketjen black in a mass ratio of 12:4.5:5.5. Step 2: The mixture of sulfur powder, corn amylopectin and Ketjen black in a ratio of 12:4.5:5.5 was placed in a vacuum glass tube and calcined at 155°C for 12 hours at a heating rate of 5°C / min to obtain a starch / sulfur / Ketjen black composite material in a ratio of 12:4.5:5.5. Step 3: Immerse the 12:4.5:5.5 starch / sulfur / Ketjenblack composite material in 100 mL of 1 mmol / L KI and 1 mmol / L I2 aqueous solution until the supernatant is colorless. Centrifuge and dry at 40°C to obtain iodine / starch / sulfur / Ketjenblack, which is the starch-integrated catalyst / sulfur integrated cathode material.

[0025] Comparative Example 1 (without iodine and starch) Commercial sulfur powder and Ketjen black were mixed evenly at a mass ratio of 12:10 and placed in a vacuum glass tube. The mixture was then calcined at 155°C for 12 hours at a heating rate of 5°C / min to obtain a 12:10 sulfur / Ketjen black composite material.

[0026] Comparative Example 2 (Physical mixing of starch and sulfur / Ketjen Black) Step 1: Mix commercial sulfur powder and Ketjen black at a mass ratio of 12:7 and place them in a vacuum glass tube. Calcine the mixture at 155°C for 12 hours at a heating rate of 5°C / min to obtain a 12:7 sulfur / Ketjen black composite material.

[0027] Step 2: Mix the 12:7 sulfur / Ketjenblack composite material with starch at a ratio of 19:3 by ball milling at a speed of 300 rpm to obtain the starch-sulfur / Ketjenblack composite material.

[0028] Comparative Example 3 (Positive electrode does not contain iodine) Step 1: Commercial sulfur powder, corn amylopectin and Ketjen black are ball-milled and mixed evenly at a mass ratio of 12:3:7 at a ball mill speed of 300 rpm to obtain a mixture of sulfur powder, corn amylopectin and Ketjen black in a mass ratio of 12:3:7. Step 2: The mixture of sulfur powder, corn amylopectin and Ketjen black in a 12:3:7 ratio is placed in a vacuum glass tube and calcined at 155°C for 12 hours at a heating rate of 5°C / min to obtain a starch / sulfur / Ketjen black composite material in a 12:3:7 ratio.

[0029] Comparative Example 4 (Starch and sulfur / Ketjen Black physically mixed and iodine introduced into the positive electrode) The starch-sulfur / Ketjenblack composite material prepared in Comparative Example 2 was immersed in 100 mL of 1 mmol / L KI and 1 mmol / L I2 aqueous solution until the supernatant was colorless. After centrifugation, it was dried at 40 °C to obtain the iodine / starch-sulfur / Ketjenblack composite material.

[0030] Comparative Example 5 (Iodine introduced into sulfur / Ketjen black cathode) The sulfur / Ketjenblack composite material prepared in Comparative Example 1 was immersed in 100 mL of 1 mmol / L KI and 1 mmol / L I2 aqueous solution until the supernatant was colorless. After centrifugation, it was dried at 40 °C to obtain the iodine / sulfur / Ketjenblack composite material.

[0031] Comparative Example 6 (excluding Ketjen Black and iodine) Commercial sulfur powder and corn amylopectin were ball-milled at a mass ratio of 12:3 at a speed of 300 rpm to obtain a 12:3 starch / sulfur composite material.

[0032] Figure 1 These are XRD comparison images of the cathode materials prepared using Embodiment 1, Comparative Example 1, Comparative Example 3, and Comparative Example 6 of the present invention. Figure 1 It was found that in all samples containing calcined starch and sulfur, the original XRD peaks of starch and sulfur completely disappeared, ultimately exhibiting an amorphous state. This indicates that during the calcination process, starch and sulfur underwent a chemical interaction, causing a change in their original crystalline structure. It is noteworthy that the sulfur / Ketjenblack composite material also exhibited an amorphous structure, which is due to the physical confinement effect of the carbon porous structure of Ketjenblack on the sulfur nanoparticles.

[0033] Figure 2 This is a Raman comparison diagram of the cathode materials prepared using Examples 1, 1, 3, and 6 of this invention. The purpose is to further investigate the changes in chemical bonds during the calcination of starch and sulfur. Among all samples containing both starch and calcined sulfur, at 323 cm⁻¹... 1 A new peak appeared, which is the vibration peak of the CS bond, indicating that the cyclic S8 molecule was successfully opened by calcination and linked to the starch skeleton by CS bonds to form a starch / linear sulfur structure.

[0034] Figure 3 The material and starch were prepared using the method described in Comparative Example 6 of this invention. 13 The comparison of C NMR spectra is intended to further investigate the binding sites of sulfur and starch. Figure 3It is known that when starch and sulfur are calcined, the NMR peak of the C1 site of starch shifts to a higher chemical shift, indicating that the C1 site of starch is bonded to the sulfur terminus, ultimately leading to the transfer of electrons from the C1 site to the sulfur terminus. It should be noted that, compared to the Raman peak position of standard elemental sulfur, the peak of the SS bond in all samples containing calcined starch and sulfur shifts to a higher Raman shift. This further proves that the formation of the CS bond causes electrons to transfer from the low electronegativity carbon atom to the high electronegativity sulfur atom, resulting in an electron-rich state for sulfur and ultimately changing its polarity. It is important to note that the optimal calcination temperature for this invention is 145℃-195℃, preferably 155℃, because at this temperature both amylopectin and sulfur are in a molten state, which is conducive to sufficient contact between linear sulfur and starch to achieve chemical bonding. Too low a temperature will result in both being in a solid state, making it difficult to achieve chemical bonding between linear sulfur and starch; too high a temperature will cause starch to decompose and carbonize, leading to starch deactivation. In addition, the optimal mass ratio of sulfur, starch and Ketjen black is 12:1.5-4.5:8.5-5.5. When the starch content is too low, the starch C1 affinity potential point is insufficient, making it difficult to fully integrate linear sulfur into the starch backbone. When the starch content is too high, the electrode conductivity will decrease, further hindering the electrode conductivity.

[0035] When iodine is further introduced into the starch / sulfur / Ketjen black composite material, at 160 cm 1 A new peak also appeared, which belongs to I5. The signal superimposed on the SS key. I5 The formation of this is due to the complexation of hydrogen bonds in the polyhydroxyl structure of starch with iodine. Compared to traditional I3... Catalyst, I5 The catalyst has a higher oxidation state, which will help enhance the catalytic oxidation of ZnS by the iodine catalyst.

[0036] Therefore, starch, as a bridging agent, not only transforms the electrochemically inert cyclic S8 molecule into highly electrochemically active linear sulfur, but also activates the more oxidizing I5. Catalysts, which will help achieve rapid sulfur conversion kinetics.

[0037] The aqueous zinc-sulfur battery cathode materials prepared in Example 1 and Comparative Examples 1-5 are then assembled into batteries and their electrochemical performance is tested.

[0038] First, an aqueous zinc-sulfur battery cathode was prepared. Specifically, the aqueous zinc-sulfur battery cathode material prepared in Example 1 and Comparative Examples 1-5, conductive carbon black Super P, and guar gum were mixed thoroughly in water at a mass ratio of 7:2:1. Then, the mixture was evenly coated onto a circular carbon cloth with a diameter of 10 mm. Finally, it was dried at 40°C for 12 h to obtain the aqueous zinc-sulfur battery cathode.

[0039] Then, the electrolyte is prepared as follows: Taking the preparation of an electrolyte with a total volume of 5 mL as an example, 3.65 g of Zn(OTF)2 is weighed and dissolved in 5 mL of a mixed solution of tetraethylene glycol dimethyl ether (G4) and water in a volume ratio of 2:3, resulting in electrolyte 1 labeled as G4 / 2M Zn(OTF)2. Then, 0.011 g of I2 is dissolved in electrolyte 1, resulting in electrolyte 2 labeled as G4 / 2M Zn(OTF)2 / I2.

[0040] Finally, the prepared positive electrode sheet was placed into a CR2032 positive electrode shell, followed by a glass fiber separator. For the positive electrode materials of Examples 1, 4, and 5, G4 / 2M Zn(OTF)2 was used as the electrolyte, and for the positive electrode materials of Comparative Examples 1-3, G4 / 2M Zn(OTF)2 / I2 was used as the electrolyte. The electrolyte volume was 100 μL in all cases. A zinc sheet with a diameter of 15 mm and a thickness of 100 μm was then placed on top of the separator, followed by a gasket and a spring sheet. Finally, the negative electrode shell was attached, and the battery was sealed using a battery packaging machine to obtain an aqueous zinc-sulfur battery.

[0041] When testing the electrochemical performance of the aqueous zinc-sulfur battery prepared above, the electrochemical window was 0.1-1.5 V; the areal loading of the active material, calculated based on the mass of sulfur, was 1.5-1.8 mg cm⁻¹. 2 .

[0042] Figure 4 The aqueous zinc-sulfur battery assembled using the positive electrode materials prepared in Example 1 and Comparative Example 1 of this invention is tested at 0.1 A g. 1 A comparison of charge and discharge curves. (From...) Figure 4 It can be seen that, compared with the traditional sulfur / Ketjenblack composite material, the charge and discharge platform of the prepared iodine / starch / sulfur / Ketjenblack integrated cathode material has been improved, further proving that the integrated cathode material has a lower redox barrier.

[0043] Figure 5 The aqueous zinc-sulfur battery assembled using the cathode materials prepared in Comparative Examples 2 and 3 of this invention, at a speed of 0.1 A g... 1The purpose of comparing the charge-discharge curves below is to investigate the reason for the decrease in the sulfur reduction energy barrier. Figure 5 As shown, compared to Comparative Example 2 (a composite material of starch and sulfur / Ketjenblack physically mixed), Comparative Example 3 (a starch / sulfur / Ketjenblack composite material prepared by melt co-loading) has a higher discharge platform, indicating that the linear sulfur structure formed by calcination of starch and sulfur has a lower reduction energy barrier than the cyclic S8 molecule.

[0044] Figure 6 Further research is needed to understand why the stable linear sulfur structure of starch has a lower reduction energy barrier. For example... Figure 6 As shown in Figure a, compared to the cyclic S8 molecule (2.1 Å), the starch / sulfur structure has a longer SS bond length (2.2 Å), indicating that the interaction between sulfur atoms in the stable linear sulfur structure of starch is weaker, and the chemical bonds are more easily broken. Furthermore, from... Figure 6 As shown in b, compared to the nonpolar cyclic S8 molecule, the stable linear sulfur structure of starch has stronger polarity. This polar structure helps to enhance the interaction with Zn. 2+ The polar interactions between them accelerate the uptake of ions. For example... Figure 6 As shown in Figure c, thanks to the easier breakage of the SS bonds in linear sulfur and the enhanced zinc affinity, starch-stabilized linear sulfur exhibits a lower electrochemical activation energy (from 71.4 kJ / mol) compared to cyclic S8 molecules. 1 Reduced to 24.6 kJ mol 1 ).

[0045] Figure 7 The aqueous zinc-sulfur battery assembled using the cathode materials prepared in Comparative Examples 4 and 5 of this invention, at a speed of 0.1 A g... 1 The comparison of charge-discharge curves below aims to investigate the reason for the decrease in the oxidation energy barrier of zinc sulfide. Compared with Comparative Example 5 (iodine with I3), The first example (iodine was introduced into the sulfur / Ketjen black cathode in the form of iodine / starch) showed a lower charging plateau compared to the second example (iodine was introduced into the sulfur / Ketjen black cathode in the form of iodine / starch). This indicates that starch-activated I5 Catalysts are more conducive to promoting the oxidation process of ZnS.

[0046] Figure 8 Further research on starch-activated I5 The reason why catalysts effectively lower the oxidation energy barrier of ZnS. For example... Figure 8 As shown in Figure a, under the same reaction time and ZnS concentration, no polyiodide signal was generated in the supernatant after mixing iodine / starch with ZnS, indicating that I5 Complete oxidation of ZnS was achieved. However, in I3 The supernatant after mixing with ZnS still contains significant amounts of I3. Signal, indicating I3 Its oxidation ability is relatively weak, making it difficult to achieve complete oxidation of ZnS. Figure 8 b and c are respectively a mixture of zinc sulfide and iodine / starch, and I3. The XRD and Raman spectroscopy comparisons of the products after solution treatment aim to further investigate the chemical composition of the reaction products. Both the XRD and Raman spectra reveal I5 The catalyst can completely oxidize ZnS to S, while conventional I3... The catalyst is insufficient to achieve complete oxidation of ZnS. Therefore, starch-activated I5... The catalyst has stronger oxidizing properties, enhances the chemical oxidation ability of ZnS, and effectively reduces the oxidation energy barrier of ZnS.

[0047] Figure 9 This is a comparison chart of the rate performance of aqueous zinc-sulfur batteries assembled using the cathode materials prepared in Example 1 and Comparative Examples 1-3 of this invention at different current densities. Figure 9 It can be seen that, thanks to the combination of starch and catalyst / sulfur structure to facilitate the sulfur redox process, the prepared integrated electrode achieves excellent rate performance. Specifically, the integrated electrode at 0.1 A g... 1 Achieving 1619 mAh g at current density 1 The reversible capacity, when the current density increases to 0.5, 1, 2, 3, 4 and 5 A g, respectively. 1 At that time, the capacity remained at 1474, 1299, 1104, 939 and 829 mAh g, respectively. 1 When the current density recovers to a low rate, its capacity recovery rate reaches 97%, indicating its excellent rate performance and reversibility. The rate performance of the integrated electrode prepared in Example 1 is far superior to that of the cathode materials in Comparative Examples 1-3, which further proves the necessity and superiority of the catalyst / sulfur integrated electrode design.

[0048] Figure 10 These are in-situ ultraviolet spectra comparisons of the positive electrode materials prepared using Example 1 and Comparative Examples 1-3 of this invention, and the resulting aqueous zinc-sulfur batteries, during the charge and discharge process. Figure 10It can be seen that, compared with the cathodes of Comparative Examples 1-3, the cathode material prepared in Example 1 did not have the dissolution of polyiodide intermediates during the overall charge and discharge process. This indicates that the iodine catalyst is complexed in the integrated cathode by the starch polyhydroxy structure, effectively suppressing the shuttle effect of the iodine catalyst and ensuring the catalytic oxidation ability of iodine on the sulfur cathode during long-cycle processes. This will help improve the reversibility of aqueous zinc-sulfur batteries.

[0049] Figure 11 Aqueous zinc-sulfur batteries assembled using the cathode materials prepared in Example 1 and Comparative Examples 1-3 of this invention, at 5 A g 1 The comparison chart below shows the long-cycle performance of the battery, and its purpose is to further study the long-cycle performance of the battery. Compared with the cathodes of Comparative Examples 1-3, the integrated cathode material prepared in Example 1 exhibits better performance at 5 A g. 1 It exhibits 730mAh g at current density 1 It boasts excellent initial capacity and operates stably for 1300 cycles with a capacity retention rate close to 100%, demonstrating long-cycle performance far superior to other comparative examples 1-3.

[0050] In summary, this invention, based on the colorimetric reaction of starch and iodine, fixes iodine within the starch double helix structure through hydrogen bonding interactions between iodine and the polyhydroxyl groups of starch. This suppresses the shuttle effect of polyiodides, effectively enriches the iodine catalyst on the positive electrode side, and maximizes its catalytic oxidation capacity. Simultaneously, it activates the highly oxidizing I5. The catalyst enhances the chemical oxidation of the discharge product ZnS, effectively lowering the oxidation energy barrier of ZnS. Furthermore, the nucleophilic sulfur chain binds to the electrophilic C1 sites in the starch backbone via CS bonds, transforming the electrochemically inert cyclic sulfur into highly electrochemically active chain sulfur. The starch-stabilized chain sulfur possesses longer SS bond lengths and stronger polarity, effectively reducing the SS bond dissociation energy and enhancing the interaction between S and Zn. 2+ The polar interaction between them significantly reduces the reduction energy barrier of sulfur. The prepared cathode material has the advantages of high specific energy, high rate capability, and high stability, which can meet the application needs of the future energy storage market.

[0051] This invention mainly utilizes starch to activate I5, which has strong oxidizing properties. The catalyst enhances the chemical oxidation of the reduction product ZnS by the iodine catalyst, thereby lowering the oxidation energy barrier of ZnS and accelerating the charging reaction kinetics of aqueous zinc-sulfur batteries. This invention not only utilizes starch to activate I5, which has strong oxidizing properties... The catalyst enhances the chemical oxidation of the reduction product ZnS by the iodine catalyst. Furthermore, by utilizing the nucleophilic reaction between the nucleophilic sulfur chain and the electrophilic C1 site in the starch backbone at high temperatures, the electrochemically inert cyclic sulfur is transformed into highly electrochemically active chain sulfur. This effectively lowers the S-S bond dissociation energy and enhances the polar interaction between S and Zn²⁺, significantly reducing the sulfur reduction energy barrier and improving the reduction kinetics of the sulfur cathode. Therefore, this invention uses starch as a bridging medium to integrate the iodine catalyst and highly electrochemically active linear sulfur, synergistically optimizing the sulfur redox kinetics. Based on the dual improvement in sulfur redox kinetics, the cathode material prepared using the method of this invention exhibits high specific energy (1120 Wh kg based on the mass of the active substance sulfur). 1 High magnification (5 Ag) 1 It still maintains 829 mAh g at current density 1 ) and high stability (5 Ag) 1 With its advantage of maintaining nearly 100% capacity after 1300 cycles at current density, it can meet the application needs of the future energy storage market.

[0052] 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 starch-integrated catalyst / linear sulfur integrated aqueous zinc-sulfur battery cathode material, characterized in that, Includes the following steps: Step 1: Weigh a certain amount of starch, sulfur, and Ketjen black and mix them evenly to obtain a mixture of starch, sulfur, and Ketjen black. Step 2: The mixture of starch, sulfur and Ketjenblack is calcined in a vacuum environment to obtain a starch / sulfur / Ketjenblack composite material. Step 3: Immerse the starch / sulfur / Ketjen black composite material in a polyiodide aqueous solution until the supernatant is colorless. After centrifugation and drying, a starch-integrated catalyst / linear sulfur integrated aqueous zinc-sulfur battery cathode material is obtained.

2. The preparation method of a starch-integrated catalyst / linear sulfur integrated aqueous zinc-sulfur battery cathode material according to claim 1, characterized in that, In step one, the mass ratio of sulfur, starch and Ketjen black is 12:1.5-4.5:8.5-5.

5.

3. The method for preparing a starch-integrated catalyst / linear sulfur integrated aqueous zinc-sulfur battery cathode material according to claim 1, characterized in that, In step one, the starch used is amylopectin.

4. The preparation method of a starch-integrated catalyst / linear sulfur integrated aqueous zinc-sulfur battery cathode material according to claim 1, characterized in that, In step one, the mixing method used is ball milling.

5. The preparation method of a starch-integrated catalyst / linear sulfur integrated aqueous zinc-sulfur battery cathode material according to claim 4, characterized in that, In step one, the ball milling speed during the ball milling mixing process is 100rpm-300rpm.

6. The method for preparing a starch-integrated catalyst / linear sulfur integrated aqueous zinc-sulfur battery cathode material according to claim 1, characterized in that, In step two, the mixture of starch, sulfur, and Ketjen black is placed in a vacuum quartz glass tube for calcination.

7. The preparation method of a starch-integrated catalyst / linear sulfur integrated aqueous zinc-sulfur battery cathode material according to claim 1, characterized in that, In step two, the calcination temperature is 145℃-195℃, the heating rate is 2℃ / min-10℃ / min, and the calcination time is 6h-24h.

8. The method for preparing a starch-integrated catalyst / linear sulfur integrated aqueous zinc-sulfur battery cathode material according to claim 1, characterized in that, In step three, I2 and KI are dissolved in 100 mL of ultrapure water at a molar ratio of 1:1 to prepare a polyiodide aqueous solution; wherein the molar concentration of I2 and KI is 1 mmol / L.

9. The preparation method of a starch-integrated catalyst / linear sulfur integrated aqueous zinc-sulfur battery cathode material according to claim 1, characterized in that, In step three, the drying temperature is 30℃-50℃.

10. A starch-integrated catalyst / linear sulfur integrated aqueous zinc-sulfur battery cathode material, characterized in that, It is prepared by any one of the preparation methods described in claims 1-9.

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