Sulfone-based hydrocarbon membranes with decentralized ion-transport channels and carbon coating for a polysulfide-based redox flow battery

Abstract

The present invention relates to sulfuryl hydrocarbon membranes having distributed ion transport channels and a carbon coating to obtain many small sized ion transport channels to mitigate cross permeation of polysulfides without sacrificing ionic conductivity. The developed sulfone-based membranes exhibit higher ion selectivity and higher ion conductivity at very low costs (12 dollars per square meter) compared to commercial fluorinated Nafion membranes. This low cost membrane enables a polysulfide-ferrocyanide redox flow total battery to perform 1600 cycles (gt, 6 months) at a current density of 20 mA cm <-2 > with a high coulombic efficiency (gt, 99.9%), an energy efficiency (gt, 75%) and a low capacity fading rate (0.0027% / day). The implementation scheme has proved that the cross permeation bottleneck of a polysulfide-based flow battery can be solved, the dependence on an expensive fluorinated Nafion membrane is eliminated, and an opportunity is provided for beneficial commercialization.

Description

(19) State Intellectual Property Office (12) Invention Patent Application (10) Publication Number (43) Publication Date (21) Application Number 202480072791.0 (22) Application Date 2024.11.18 (30) Priority Data 63 / 599,593 2023.11.16 US 63 / 611,263 2023.12.18 US (85) PCT International Application Entering National Phase Date 2026.05.15 (86) PCT International Application Application Data PCT / CN2024 / 132675 2024.11.18 (87) PCT International Application Publication Data WO2025 / 103503 EN 2025.05.22 (71) Applicant: The Chinese University of Hong Kong Address: Sha Tin, New Territories, Hong Kong, China (72) Inventors: Lu Yijun, Wang Feiran (74) Patent Agency: Beijing Gaowo Law Firm 11569 Patent Attorney: Wang Zixuan (51) Int.Cl. H01M 8 / 18 (2006.01) H01M 8 / 0239 (2016.01) (54) Invention Title: Sulfone-based hydrocarbon membrane with dispersed ion transport channels and carbon coating for polysulfide-based redox flow batteries (57) Abstract: This invention relates to a sulfone-based hydrocarbon membrane having dispersed ion transport channels and a carbon coating to obtain a number of small-sized ion transport channels, thereby mitigating polysulfide cross-permeability without sacrificing ion conductivity. Compared with commercially available fluorinated Nafion membranes, the developed sulfone-based membrane exhibits higher ion selectivity and higher ion conductivity at a very low cost (US$12 / m²). This low-cost membrane enables polysulfide-ferrocyanide redox flow batteries to achieve 1600 cycles (>6 months) at a current density of 20 mA cm⁻² with high coulombic efficiency (>99.9%), energy efficiency (>75%), and low capacity decay rate (0.0027% / day). The embodiments have demonstrated the ability to overcome the cross-permeation bottleneck of polysulfide-based flow batteries, eliminate dependence on expensive fluorinated Nafion membranes, and provide opportunities for beneficial commercialization. Claims 2 pages, Description 21 pages, Drawings 41 pages. CN 122207122 A 2026.06.12 CN 1 22 20 71 22 A 1. A polysulfide-based redox flow battery, comprising: a sulfonated sulfone hydrocarbon membrane having a plurality of dispersed ion transport channels. 2. The battery according to claim 1, wherein the sulfonated sulfone-based hydrocarbon membrane comprises at least one polysulfone selected from the following: sulfonated polyether sulfone (SPES), sulfonated polysulfone (SPSF), sulfonated polyphenylene sulfone (SPPSU), sulfonated polyarylene sulfide sulfone (SPSS), and sulfonated polyarylene sulfone (SPAES).3. The battery of claim 2, wherein the polysulfone has a rigid hydrophobic aromatic polymer backbone comprising a plurality of aromatic rings, each ring comprising a plurality of hydrogen atoms. 4. The battery of claim 3, wherein at least one sulfonate or sulfonic acid group replaces any hydrogen atom on any aromatic ring in the rigid hydrophobic aromatic polymer backbone. 5. The battery of claim 2, wherein the degree of sulfonation of at least one polysulfone is at least about 10%. 6. The battery of claim 2, wherein the degree of sulfonation of at least one polysulfone is at least about 30%. 7. The battery of claim 2, wherein the degree of sulfonation of at least one polysulfone is at least about 50%. 8. The battery of claim 1, wherein the sulfonated sulfone-based hydrocarbon film comprises a surface modification that effectively controls the swelling of the sulfone-based hydrocarbon film. 9. The battery of claim 8, wherein the surface modification comprises a carbon coating. 10. The battery of claim 1, wherein the thickness of the sulfone-based hydrocarbon film is less than 190 μm. 11. A sulfonated sulfone-based hydrocarbon membrane for redox flow batteries, comprising: sulfonated polyether sulfone (SPES), wherein the sulfonated polyether sulfone (SPES) has a sulfonation degree of about 30% and a thickness of about 150 μm, wherein the sulfone-based hydrocarbon membrane has multiple dispersed ion transport channels, the water channel density of the dispersed ion transport channels is about 0.85 g cm⁻³, there are about 3 hydrophilic ion transport channels per square nanometer on average, and the water cluster diameter is about 1.65 nm, thereby the sulfonated sulfone-based hydrocarbon membrane exhibits: a water / electrolyte absorption rate of about 14% in water, a water / electrolyte absorption rate of about 13% in 1 M KOH, and a water / electrolyte absorption rate of about 12% in KCl aqueous solution; a swelling rate of about 23% in water, a swelling rate of about 19% in KOH, and a swelling rate of about 19% in 1 M KCl aqueous solution; a tensile strength of about 32 MPa; and an elongation at break of about 200%. 12. The sulfonated sulfone-based hydrocarbon membrane according to claim 11 further comprises a carbon coating having a thickness of about 10 μm on each side of the membrane and a carbon loading of about 0.23 mg cm⁻², the carbon coating being formed from a slurry comprising about 50 mg carbon (KB), about 6 mg PTFE, and isopropanol (IPA):water in a volume ratio of about 7:3. 13. A polysulfide-ferrocyanide redox flow battery comprising: a sulfonated polyether sulfone (SPES) membrane as defined in claim 11; a positive electrode electrolyte comprising 0.5 M K₄[Fe(CN)₆] and 1 M KCl as a supporting electrolyte; and a negative electrode electrolyte comprising 1 M K₂S₄ dissolved in 1 M KOH solution and 50 mM FMN-Na as a molecular catalyst; thereby, the polysulfide-ferrocyanide redox flow battery exhibits:At least approximately 99.4% coulombic efficiency (CE), at least approximately 83.1% energy efficiency (EE) at a current density of approximately 20 mA cm⁻², a cycle life of more than 1000 hours, and a capacity decay rate of less than approximately 0.0004% / cycle or less than approximately 0.0034% / day. 14. The polysulfide-ferrocyanide redox flow battery according to claim 13, wherein the sulfonated polyether sulfone (SPES) membrane further comprises a carbon coating having a thickness of about 10 μm on each side of the membrane and a carbon loading of about 0.23 mg cm⁻², wherein the battery exhibits: at least about 99.9% coulombic efficiency (CE); at least about 82.2% energy efficiency (EE) at a current density of about 20 mA cm⁻²; a cycle life greater than about 6 months; and a capacity decay rate of less than about 0.0004% / cycle or less than about 0.0032% / day. 15. A method for preparing a sulfonated sulfone-based hydrocarbon membrane for a redox flow battery, comprising: drying sulfonated polyether sulfone (SPES) polymer powder at about 50°C to prepare dried SPES powder; dissolving the dried SPES polymer powder in N,N-dimethylacetamide to form a 30 wt.% SPES casting solution at a temperature of about 25°C; degassing the SPES casting solution; pouring the SPES casting solution onto a plate at a temperature of about 25°C and a relative humidity of less than 25%; scraping the solution with a doctor blade at a speed of about 0.12 m min⁻¹ to form a wet film with a thickness of about 800 μm; drying the wet film at about 80°C for at least about 8 hours to form a dried sulfonated sulfone-based hydrocarbon membrane with a thickness of about 150 μm; peeling the dried sulfonated sulfone-based hydrocarbon membrane off the plate; and immersing the dried sulfonated sulfone-based hydrocarbon membrane in deionized water (DI). 16. The method of claim 15, further comprising: immersing the wet sulfonyl hydrocarbon membrane in a 5 wt.% aqueous solution of H₂SO₄ at about 80°C for at least 1 hour; cooling the sulfonyl hydrocarbon membrane to about 25°C; washing the sulfonyl hydrocarbon membrane with deionized water, and then immersing it in deionized water at about 25°C for at least 1 hour; immersing the sulfonyl hydrocarbon membrane in a 1 M KOH aqueous solution at about 80°C for at least 2 hours; cooling the sulfonyl hydrocarbon membrane a second time to about 25°C; washing the sulfonyl hydrocarbon membrane again with deionized water, and then immersing it in deionized water at about 25°C for at least 1 hour to obtain a sulfonyl hydrocarbon membrane with a final thickness of about 150 μm to about 155 μm; and immersing the sulfonyl hydrocarbon membrane in deionized water before use. 17. The method of claim 15, further comprising:Wipe the sulfonated sulfone hydrocarbon membrane to remove excess liquid; sandwich the sulfonated sulfone hydrocarbon membrane between two PTFE gaskets; provide a carbon-containing slurry, wherein for every 50 mg of carbon (KB), there is 0.15 mL of 5% PTFE dispersion, 3.5 mL of IPA, and 1.5 mL of deionized water; mix the carbon-containing slurry and sonicate it for at least about 20 minutes while cooling it with ice water; coat each side of the sulfonated sulfone hydrocarbon membrane with the carbon-containing slurry; heat-dry the sulfonated sulfone hydrocarbon membrane, gaskets, and slurry in an oven at about 80°C for at least 12 hours; and immerse the sulfonated sulfone hydrocarbon membrane in deionized water for at least 24 hours. Claims 2 / 2 Page 3 CN 122207122 A Sulfone-based hydrocarbon membrane for polysulfide-based redox flow batteries with distributed ion transport channels and carbon coating Cross-reference to related applications

[0001] This application claims the benefit of U.S. Provisional Application No. 63 / 599,593, filed November 16, 2023, and U.S. Provisional Application No. 63 / 611,263, filed December 18, 2023, the disclosures of which are incorporated herein by reference in their entirety. Background Art

[0002] The development of grid-scale energy storage systems is crucial for the large-scale deployment of renewable energy.1,2 Aqueous redox flow batteries (ARFBs) are among the most promising large-scale grid energy storage technologies due to their inherent safety, design flexibility, and long service life.3,4,5 Vanadium redox flow batteries (VRFBs) are the most mature ARFBs; however, their high cost ($89.4 / kWh) and the limited availability of vanadium resources restrict their widespread application. Polysulfide-based redox flow batteries (PSFBs)6,7,8 are highly attractive emerging flow battery systems due to the ultra-low cost ($0.15 / kWh) and abundant availability of polysulfides (54 × 106 tons / year). The main challenge of PSFBs is the crossover of polysulfides, which leads to irreversible capacity loss, and electrode / film passivation caused by the oxidation of polysulfides to insulating solid sulfur. These fundamental reasons result in the poor cycle life of PSFBs (<50 cycles) and hinder their practical application9,10,11 Studies have shown that a modified commercial perfluorosulfonic acid-based membrane (Nafion™, e.g., Nafion 117 or N117, Chemours, Wilmington, Delaware, USA) can effectively mitigate the cross-permeation of polysulfides12 (Li, Z. & Lu, Y.–C. Nature Energy 2021, 6, 517–528). However, the high cost of fluorinated Nafion™ membranes (US$800 / m²) remains a concern.The price of $3,500 per square meter remains a strong deterrent to its commercial application.

[0003] Ion exchange membranes play a crucial role in ion transport and ion selection between the positive and negative electrolytes, and are expected to provide high ionic conductivity while inhibiting cross-permeation of active materials.13 Microphase separation occurs when polymer molecules stack and self-assemble to build a polymer matrix.14 For example, the formation mechanism of ion transport channels in Nafion is shown in Figure 1A. The phase regions formed by the hydrophobic perfluorinated backbone and the hydrophilic sulfonic acid groups tend to separate, forming hydrophobic and hydrophilic phase regions. These hydrophilic regions in the polymer matrix interconnect to build continuous water channels for ion transmembrane transport. This centralized cluster network results in excessively large ion transport channels in the Nafion membrane, leading to high ionic conductivity but poor ion selectivity.15

[0004] The embodiments provide a series of novel and advantageous sulfone-based hydrocarbon membranes having dispersed ion transport channels and a carbon coating to achieve “small and numerous” ion transport channels, thereby mitigating polysulfide cross-permeation without sacrificing ion conductivity. In some embodiments, the size and distribution of ion transport channels can be tuned via microphase separation in the polymer matrix by controlling the comonomer and degree of sulfonation. Sulfone-based membranes exhibit high water absorption (e.g., high ion conductivity) and strong structural stability (e.g., low swelling rate) thanks to the hydrophilic sulfonic acid groups (-SO3H), sulfone groups (-SO2-), and rigid aromatic backbone. According to some embodiments of the invention, small-angle X-ray scattering (SAXS) and atomic force microscopy (AFM) have been used to characterize the size and distribution of the ion transport channels in the provided membranes. The developed low-cost sulfone-based membrane (e.g., $12 / m²) exhibits superior flow battery performance compared to commercial fluorinated Nafion (e.g., $800 / m² to $3500 / m²), enabling fully polysulfide-ferrocyanide (S-Fe) redox flow batteries (RFBs) to stably cycle for more than 1600 cycles (e.g., >6 months) at 20 mA cm⁻², with high coulombic efficiency (e.g., >99.6%) and low capacity decay rate (e.g., 0.0034% / day).

[0005] One embodiment relates to a polysulfide-based redox flow battery employing a sulfonated sulfone-based hydrocarbon membrane having multiple dispersed ion transport channels. The sulfonated sulfone-based hydrocarbon film may contain at least one of the following polysulfones: sulfonated polyether sulfone (SPES), sulfonated polysulfone (SPSF), sulfonated polyphenylene sulfone (SPPSU), and sulfonated polyarylene sulfone.(SPSS) and sulfonated polyarylether sulfone (SPAES). The polysulfone has a rigid hydrophobic aromatic polymer backbone with multiple aromatic rings, each ring containing multiple hydrogen atoms, wherein one or more hydrogen atoms are replaced by sulfonate or sulfonic acid groups. The degree of sulfonation can be at least 10%, at least 30%, or at least 50%. The thickness of the sulfone-based hydrocarbon membrane can be less than 190 μm. The sulfone-based hydrocarbon membrane has a surface modification that effectively controls the swelling of the sulfone-based hydrocarbon membrane. The surface modification can be a carbon coating.

[0006] In an embodiment, a sulfonated sulfone-based hydrocarbon membrane for a redox flow battery has multiple dispersed ion transport channels with a water channel density of about 0.85 g cm⁻³, showing about 3 hydrophilic regions per square nanometer on average, wherein the degree of sulfonation of the sulfonated polyether sulfone (SPES) is about 30%, the thickness is about 150 μm, and the diameter of the water clusters in the membrane is about 1.65 nm. The sulfone-based hydrocarbon membrane exhibits a water / electrolyte absorption rate of approximately 14% in water, approximately 13% in 1 M KOH, and approximately 12% in an aqueous KCl solution; its swelling ratio is approximately 23% in water, approximately 19% in KOH, and approximately 19% in an aqueous 1 M KCl solution; its tensile strength is approximately 32 MPa, and its elongation at break is approximately 200%. The sulfone-based hydrocarbon membrane can have a coating formed from a slurry containing approximately 50 mg KB, approximately 6 mg PTFE, and an IPA:water ratio of approximately 7:3 by volume, resulting in a coating with a thickness of approximately 10 μm on each side of the membrane and a KB loading of approximately 0.23 mg cm⁻².

[0007] In one embodiment, a polysulfide-ferrocyanide redox flow battery comprises: a positive electrode electrolyte consisting of 0.5 M K4[Fe(CN)6] and 1 M KCl supporting electrolytes; a negative electrode electrolyte consisting of 1 M K2S4 dissolved in 1 M KOH solution and 50 mM FMN-Na as a molecular catalyst; and a sulfonated polyethersulfone (SPES) membrane exhibiting at least about 99.4% coulombic efficiency (CE), at least about 83.1% energy efficiency (EE) at a current density of about 20 mA cm⁻², a cycle life of more than 1000 hours, and a capacity decay rate of less than about 0.0004% / cycle or less than about 0.0034% / day. The polysulfide-ferrocyanide redox flow battery can have a sulfonated polyethersulfone (SPES) membrane with a carbon coating to exhibit at least about 99.9% CE, at least about 82.2% EE at a current density of about 20 mA cm⁻², a cycle life of more than about 6 months, and a capacity decay rate of less than about 0.0004% / cycle or less than about 0.0032% / day.

[0008] One embodiment relates to a method for preparing a sulfonated sulfone-based hydrocarbon membrane for a redox flow battery, wherein sulfonated polyether sulfone (SPES) polymer powder is dried at about 50°C for about 6 hours to prepare dried SPES powder, and dissolved in DMAC (N,N-dimethylacetamide) to form a 30 wt.% SPES casting solution at a temperature of about 25°C, wherein the SPES casting solution is deposited and spread on a glass plate with a doctor blade to form a wet film with a thickness of about 800 μm, then dried at about 80°C for at least about 8 hours to form an SPES membrane, and a membrane with a thickness of about 150 μm is peeled off, and then the membrane is immersed in deionized water (DI water). The sulfonyl hydrocarbon membrane can then be further processed as follows: the SPES membrane is immersed in a 5 wt.% aqueous H2SO4 solution at about 80°C for at least 1 hour, the SPES membrane is cooled to about 25°C, the SPES membrane is washed with deionized (DI) water, and then immersed in deionized water at about 25°C for at least 1 hour. The SPES membrane is then immersed in a 1 M KOH aqueous solution at about 80°C for at least 2 hours, the SPES membrane is cooled to about 25°C, and the SPES membrane is washed with deionized water. Finally, the SPES membrane is immersed in deionized water at about 25°C for at least 1 hour to obtain a SPES membrane with a final thickness of about 150 μm to about 155 μm. The SPES membrane can also be further processed as follows: wipe the SPES membrane to remove excess liquid, sandwich the SPES membrane between two PTFE pads, prepare a slurry containing 50 mg KB, 0.15 mL 5% PTFE dispersion, 3.5 mL IPA and 1.5 mL deionized water, and coat the slurry onto each side of the SPES membrane at a coating amount of about 110 μL. Then heat-dry the SPES membrane, pads and slurry in an oven at about 80°C for at least 12 hours, and store the SPES membrane in deionized water for at least 24 hours before use. The accompanying drawings contain at least one color drawing. The Patent Office will provide a copy of the published patent or patent application with color drawings upon request and payment of the necessary fees.

[0009] Figure 1A illustrates the phase separation performance for forming an ion transport channel according to one embodiment, showing a polymer self-assembled centralized ion transport channel of the Nafion membrane.

[0010] FIG1B illustrates a dispersed ion transport channel of a sulfone hydrocarbon membrane regulated by a comonomer according to an embodiment.

[0011] FIG1C illustrates a comonomer contained in the sulfone hydrocarbon membrane of FIG1B according to an embodiment.

[0012] FIG1D illustrates the structure of a dispersed ion transport channel according to an embodiment, which depends on the comonomer of FIG1C for the sulfone hydrocarbon membrane according to an embodiment.

[0013] Figure 2A shows a comparison of the water / electrolyte absorption rates of the three ion-selective membranes and N117 according to the embodiments in three different aqueous solutions.

[0014] Figure 2B shows the swelling rates of the three ion-selective membranes and N117 according to the embodiments in three different aqueous solutions.

[0015] Figure 2C shows the water channel density of the polymer matrix of the three ion-selective membranes and N117 according to the embodiments.

[0016] Figure 2D shows the small-angle X-ray scattering spectra of the three ion-selective membranes and N117 according to the embodiments, where the measured value d represents the Bragg spacing.

[0017] Figure 2E shows the AFM tap-mode phase images of N117 and S30, where the dark areas represent the hydrophilic regions of the polymer matrix.

[0018] Figure 2F shows the areal resistivity (ASR) measured for the three ion-selective membranes and N117 according to the embodiments in two different electrolyte solutions.

[0019] Figure 2G shows the permeability of polysulfide ions through the three ion-selective membranes and N117 according to the embodiments, wherein the diffusion rate was tested at room temperature.

[0020] Figure 2H shows the mechanical properties of the three ion-selective membranes and N117 according to the embodiments, including tensile strength and elongation.

[0021] Figure 3A shows the open-circuit voltage profiles of the S30 and N117 membranes according to one embodiment.

[0022] Figure 3B shows the voltage profile of the S30 membrane according to one embodiment during a charge-discharge cycle test at a current density of 20 mA cm⁻².

[0023] Figure 3C shows the voltage profile of N117 during a charge-discharge cycle test at a current density of 20 mA cm⁻².

[0024] Figure 3D shows the battery performance of the S30 (red, >1100 hours) and N117 membranes (blue, approximately 250 hours) according to one embodiment in long-term cycle measurements.

[0025] Figure 4A schematically illustrates an aqueous polysulfide-ferrocyanide redox flow battery according to one embodiment.

[0026] Figure 4B shows the galvanostatic voltage curve of the modified Nafion base membrane.

[0027] Figure 4C shows the galvanostatic voltage curve of the modified SPES base membrane according to one embodiment.

[0028] Figure 4D shows a comparison of the voltage curves of the modified Nafion base membrane (N117-C) and the SPES base membrane (S30-C) at current densities of 20 mA cm⁻² (solid line) and 50 mA cm⁻² (dashed line) according to one embodiment.

[0029] Figure 4E shows an optical photograph of an aqueous polysulfide-ferrocyanide redox flow battery according to one embodiment, as schematically shown in Figure 4A.

[0030] Figure 4F shows the battery performance of a modified SPES-based membrane with an energy efficiency recovery procedure according to one embodiment for 180 days at a current density of 20 mA cm⁻².

[0031] Figure 5 shows a comparison of the ion exchange capacity (IEC) of Nafion resin and various sulfonated sulfone-based hydrocarbon polymers according to an embodiment.

[0032] Figure 6A shows the water / electrolyte absorption rates of the membrane and N117 membrane according to an embodiment.

[0033] Figure 6B shows the swelling rates of Nafion 117 and sulfonated polyether sulfone (SPES) with different degrees of sulfonation according to an embodiment.

[0034] Figure 6C shows a comparison of the water / electrolyte absorption rates of the membrane and N117 with / without modification according to an embodiment.

[0035] Figure 6D shows a comparison of the swelling rates of the membrane and N117 with / without modification according to an embodiment.

[0036] Figure 7A is a digital image of a battery assembly used for membrane testing according to an embodiment.

[0037] Figure 7B is a digital image of the assembled battery for electrochemical impedance spectroscopy (EIS) testing according to an embodiment.

[0038] Figure 7C is an equivalent circuit model for fitting the Nyquist plot 17 of the battery shown in Figure 7B.

[0039] Figure 7D shows the Nyquist plot of a battery containing an S10 film according to one embodiment.

[0040] Figure 8A shows the difference in areal resistivity (ASR) between films with different comonomers and N117 according to an embodiment.

[0041] Figure 8B shows the difference in ASR between films with different degrees of sulfonation (DS) and N117 according to an embodiment.

[0042] Figure 8C shows the difference in ASR between modified films and N117 according to an embodiment.

[0043] Figure 8D shows the difference in ionic conductivity between films with different comonomers and N117 according to an embodiment.

[0044] Figure 8E shows the difference in ionic conductivity between the membrane with different degrees of sulfonation (DS) and N117 according to the embodiment.

[0045] Figure 8F shows the difference in ionic conductivity between the modified membrane and N117 according to the embodiment.

[0046] Figure 9A shows the standard UV-Vis spectrum of K2S2 in 1.0 M KOH aqueous solution.

[0047] Figure 9B is a linear fitting curve of the absorbance of K2S2 concentration at 300 nm in 1.0 M KOH aqueous solution.

[0048] Figure 9C shows the standard UV-Vis spectrum of K2S4 in 1.0 M KOH aqueous solution.

[0049] Figure 9D is a linear fitting curve of the absorbance of K2S4 concentration at 300 nm in 1.0 M KOH aqueous solution.

[0050] Figure 10A shows the standard UV-Vis spectrum of K4[Fe(CN)6] in 1.0 M KOH aqueous solution.

[0051] Figure 10B is a linear fitting curve 18 of the absorbance of K4[Fe(CN)6] concentration at 300 nm in a 1.0 M KOH aqueous solution.

[0052] Figure 10C shows the standard UV-Vis spectrum 18 of K3[Fe(CN)6] in a 1.0 M KOH aqueous solution.

[0053] Figure 10D is a linear fitting curve 18 of the absorbance 18 of K3[Fe(CN)6] concentration at 300 nm in a 1.0 M KOH aqueous solution.

[0054] Figure 11A shows the S2 2− ion permeability of sulfone-based films with different degrees of sulfonation and N117 according to the embodiment. Specification 4 / 21 pages 7 CN 122207122 A

[0055] Figure 11B shows the S2 2− ion permeability of sulfone-based films with / without surface modification and N117 according to the embodiment.

[0056] Figure 12A shows a SEM image of the S30 membrane surface according to one embodiment before immersion in an aqueous solution.

[0057] Figure 12B shows a SEM image of the S30 membrane surface according to one embodiment after immersion in a 1 M K2S2-1 M KOH solution for 40 days.

[0058] Figure 12C shows a SEM image of the S30 membrane surface according to one embodiment after immersion in a 1 M K2S4-1 M KOH solution for 40 days.

[0059] Figure 12D shows a SEM image of the S30 membrane surface according to one embodiment after immersion in a 0.5 M K4[Fe(CN)6]-1 M KCl solution for 40 days.

[0060] Figure 12E shows a SEM image of the S30 membrane surface according to one embodiment after immersion in a 0.5 M K3[Fe(CN)6]-1 M KCl solution for 40 days.

[0061] Figure 12F shows a SEM image of the S30 membrane surface according to one embodiment after immersion in 50 mM riboflavin sodium phosphate (FMN-Na) for 40 days.

[0062] Figure 13 shows the FTIR spectra of the S30 membrane according to one embodiment before and after contact with K2S2, K2S4, K4[Fe(CN)6] and K3[Fe(CN)6] solutions.

[0063] Figure 14A shows a SEM image of the S30-C membrane surface according to one embodiment at a relatively low magnification.

[0064] Figure 14B shows a SEM image of the S30-C membrane surface according to one embodiment at a higher magnification than Figure 14A.

[0065] Figure 14C shows a SEM image of the S30-C membrane surface according to one embodiment at a relatively high magnification.

[0066] Figure 14D shows a SEM image of the N117-C membrane surface at a relatively low magnification.

[0067] Figure 14E shows an SEM image of the N117-C membrane surface at a higher magnification than Figure 14D.

[0068] Figure 14F shows an SEM image of the N117-C membrane surface at a relatively high magnification.

[0069] Figure 15A shows an SEM image of a cross-section of an S30-C membrane according to one embodiment at a relatively low magnification.

[0070] Figure 15B shows an SEM image of a cross-section of an S30-C membrane according to one embodiment at a higher magnification than Figure 15A.

[0071] Figure 15C shows an SEM image of a cross-section of an S30-C membrane according to one embodiment at a relatively high magnification.

[0072] Figure 15D shows an SEM image of a cross-section of an N117-C membrane at a relatively low magnification.

[0073] Figure 15E shows an SEM image of a cross-section of an N117-C membrane at a higher magnification than Figure 15D.

[0074] Figure 15F shows an SEM image of the N117-C membrane cross-section at a relatively high magnification.

[0075] Figure 16A shows an energy dispersive spectroscopy (EDS) image of the S30-C membrane cross-section according to some embodiments of the present invention.

[0076] Figure 16B shows a portion of the energy dispersive spectroscopy (EDS) image of Figure 16A at a greater magnification.

[0077] Figure 17A shows the battery performance of sulfone-based membranes with different comonomer compositions and N117 according to embodiments, wherein the coulombic efficiency (CE) and energy efficiency (EE) of the membranes at different current densities are shown.

[0078] Figure 17B shows the voltage curves of N117 and the sulfone-based membrane according to embodiments at a current density of 20 mA cm⁻². Specification 5 / 21 pages 8 CN 122207122 A

[0079] Figure 17C shows the Nyquist plot of a battery assembled from multiple membranes according to embodiments and an N117 battery.

[0080] Figure 18A shows the coulombic efficiency (CE) and energy efficiency (EE) of a cell with membranes and N117 having different degrees of sulfonation according to an embodiment at different current densities.

[0081] Figure 18B shows the coulombic efficiency (CE) and energy efficiency (EE) of a cell with surface-modified membranes and N117 having surface-modified membranes according to an embodiment at different current densities.

[0082] Figure 19 shows a SEM of a polymer matrix membrane structure with a wrinkled or folded structure associated with low Ra (e.g., less than 7) according to an embodiment, wherein the S2 2− ion permeability of the membrane is greater than 2 × 10−8 cm2 min−1.

[0083] Figure 20A shows a coating according to an embodiment having defects associated with high Ra (e.g., greater than 17) and a toner loading of less than 0.1 g cm−2 after water rinsing.

[0084] Figure 20B shows a coating according to one embodiment, which is free of defects associated with high Ra (e.g., greater than 17) and has a carbon loading of less than 0.1 g cm⁻² after water rinsing. Detailed Description

[0085] Embodiments of the present invention provide a series of sulfone-based hydrocarbon membranes having dispersed ion transport channels and carbon coatings to obtain numerous small ion transport channels, thereby mitigating polysulfide cross-permeation without sacrificing ion conductivity. In embodiments, the sulfone-based hydrocarbon membrane comprises hydrophilic sulfonic acid groups and comonomers forming a hydrophobic backbone and hydrophilic side chains. In embodiments, feasible hydrophilic sulfone monomers include, but are not limited to: sulfone, 3,3'-diphenyl-4,4'-diphenyl sulfone, 3,3',5,5'-tetraphenyl-4,4'-difluorodiphenyl sulfone, and dibenzo[b,d]thiophene sulfone. The feasible hydrophobic sulfone monomers used in the main chain of embodiments of the present invention may include, but are not limited to, monomers capable of forming the following polymers: polysulfone (PSF), polyethersulfone (PES), polyphenylene sulfone (PPSU), polyarylene sulfide sulfone (PSS), and polyarylene ether sulfone (PAES). Copolymers with sulfonated sulfones are labeled as SPPSU, SPSF, and SPES in Figure 1D, and are referred to herein as “P,” “F,” and “S,” respectively, with the number following the letter indicating the degree of sulfonation of the polymer. The feasible comonomers used in embodiments may include, but are not limited to, monomers having the following functional groups: sulfones, bisphenols, hexafluorobisphenol A, ethers, ketones, imidazoles, imides, and esters.

[0086] The degree of sulfonation in the membrane may be, but is not limited to, 10% to 50%. The number of sulfonic acid groups in the side chain, i.e., the degree of sulfonation (DS), affects the performance of the membrane. Experiments were conducted on membranes with DS of 10%, 30%, and 50%, although embodiments included membranes with DS below 10% and membranes with DS above 50%, and membranes with any DS in the range of 10% to 50% could be used. For example, DS could be 29% to 31%, 25% to 35%, 20% to 40%, or 1% to 99%, including increments, combinations, and ranges of any of the foregoing values.

[0087] Examples of observed dispersed ion transport channels include: (a) sulfonated polyether sulfone, sulfonation degree = 30%, membrane thickness = 160 μm; (b) sulfonated polysulfone, sulfonation degree = 35%, membrane thickness = 180 μm; (c) sulfonated polyphenylene sulfone, sulfonation degree = 25%, membrane thickness = 145 μm; (d) sulfonated polyarylene sulfide sulfone, sulfonation degree = 33%, membrane thickness = 195 μm; and (e) sulfonated polyarylene sulfide sulfone, sulfonation degree = 20%, membrane thickness = 125 μm. These membranes can be carbon-coated using a coating composition comprising carbon powder, solvent, and binder, wherein: the carbon can be, but is not limited to, KB (Kejtien Black), CNT (carbon nanotubes), or AC (activated carbon); and the solvent can be, but is not limited to, NMP (1-methyl-2-pyrrolidone), DMF (N,N-dimethylformamide), or DMAC (N,N-dimethylacetamide).The binder may be IPA (2-propanol), ethanol, acetone, water, or any combination thereof; the binder may be, but is not limited to, PVDF (polyvinylidene fluoride), PVDF-HFP (polyvinylidene fluoride-hexafluoropropylene copolymer), PVA (polyvinyl alcohol), and PTFE (polytetrafluoroethylene). The carbon coating may be applied to one or both sides of the membrane surface, with a thickness of approximately 5 μm to 10 μm, but not limited to this. The toner loading may be, but is not limited to, approximately 0.23 mg cm⁻², and the weight ratio of toner to binder may be, but is not limited to, approximately 8:1. Exemplary, smooth, and uniform coatings have been prepared using the following formulations: (a) a co-solvent of water and ethanol in a 3:7 (volume ratio), KB toner, and PTFE binder; (b) a co-solvent of water and NMP in a 5:5 (volume ratio), CNT toner, and PVDF binder; (c) a solvent of acetone, AC toner, and PVDF-HFP binder; and (d) a co-solvent of DMF and IPA in a 1:9 (volume ratio), KB toner, and PTFE binder; (e) a co-solvent of ethanol and IPA in a 4:6 (volume ratio), CNT toner, and PVA binder. These films have smooth and uniform surfaces, as shown in Figures 15A to 15C.

[0088] In an embodiment, a plurality of small ion transport channels are formed, wherein the water clusters have a diameter of less than 1.7 nm. Water channel density is defined as the ratio of the weight change to the volume change of the membrane when hydrated in pure water, and its value is greater than 0.5 g cm⁻³, which can mitigate the cross-permeability of polysulfides without sacrificing ionic conductivity. The size and distribution of ion transport channels formed in the polymer matrix through microphase separation can be tuned by controlling the comonomers and degree of sulfonation of the polymers used to form the membrane. Various sulfonyl hydrocarbon polymers were formed using exemplary comonomers (Figure 1C), where the ratio of sulfonated to non-sulfonated monomers is controllable; for example, when x is 0.3 in Figure 1B, the degree of sulfonation is considered to be 30% for this controlled degree of sulfonation. The degree of sulfonation has also been tuned to ranges of 10% and 50%, but is not limited to these values. The degree of sulfonation can be measured by nuclear magnetic resonance (NMR) and correlated with the ion exchange capacity (IEC). The size and distribution of ion transport channels can be characterized by small-angle X-ray scattering (SAXS) and atomic force microscopy (AFM). The membrane can be readily prepared using (but not limited to) solution casting methods.

[0089] In embodiments, the hydrophilic sulfonic acid and / or sulfonate groups and sulfone groups are bonded to the rigid aromatic backbone, causing the sulfone-based membrane to exhibit high water absorption and high ionic conductivity, for example, but not limited to, a water absorption rate of 7% to 36% and an ionic conductivity of 0.1 mS cm⁻¹ to 20 mS cm⁻¹ in a 1 M KOH aqueous solution. In exemplary membrane compositions, a water absorption rate of 10% to 15% and an ionic conductivity of 4 mS cm⁻¹ to 10 mS cm⁻¹ are observed.A high ionic conductivity of mS cm⁻¹ is advantageous for polysulfide-based redox flow batteries. As shown in Figure 1D, using the comonomers of Figure 1C, the following exemplary membranes exhibit advantageous water absorption and ionic conductivity, including: SPES (sulfonation degree = 30%), water absorption: 14.2%, ionic conductivity: 6.3 mS cm⁻¹; SPSF (sulfonation degree = 30%), water absorption: 12.4%, ionic conductivity: 5.3 mS cm⁻¹; SPPSU (sulfonation degree = 30%), water absorption: 10.7%, ionic conductivity: 5.2 mS cm⁻¹; SPSS (sulfonation degree = 25%), water absorption: 9.4%, ionic conductivity: 4.9 mS cm⁻¹; and SPAES (sulfonation degree = 35%), water absorption: 15.6%, ionic conductivity: 6.7 mS cm⁻¹. These membranes exhibit strong structural stability and low swelling rates of 3% to 40%, with 12% to 22% being advantageous in some embodiments. For example, SPES (sulfonation degree = 30%) has a swelling rate of 22.9% in pure water, 19.4% in 1 M KOH aqueous solution, and 18.7% in 1 M KCl aqueous solution; SPSF (sulfonation degree = 30%) has a swelling rate of 21.6% in pure water, 19.4% in 1 M KOH aqueous solution, and 18.1% in 1 M KCl aqueous solution; and SPES (sulfonation degree = 10%) has a swelling rate of 13.1% in pure water, 10.3% in 1 M KOH aqueous solution, and 9.7% in 1 M KCl aqueous solution.

[0090] Small-angle X-ray scattering (SAXS) and atomic force microscopy (AFM) of these exemplary membranes showed water cluster diameters of 1.20 nm to 1.70 nm. For example: SPPSU (sulfonation degree = 30%): 1.57 nm; SPSF (sulfonation degree = 30%): 1.62 nm; SPES (sulfonation degree = 30%): 1.65 nm; SPSS (sulfonation degree = 25%): 1.42 nm; and SPAES (sulfonation degree = 35%): 1.70 nm. These exemplary membranes show a distribution of 1 to 5 hydrophilic regions per 1 nm² in their AFM images. For example, SPES (sulfonation degree = 30%) has 3 hydrophilic regions per 1 nm²; SPSF (sulfonation degree = 30%) has 2 hydrophilic regions per 1 nm²; and SPPSU (sulfonation degree = 30%) has 1 hydrophilic region per 1 nm². These ion transport channels in these membranes provide favorable high ionic conductivity and low cross-permeability of reactive substances.

[0091] These sulfone-based films are inexpensive, costing approximately $12 per square meter, compared to costs ranging from $800 to $3,500 per square meter.Compared to commercially available fluorinated Nafion membranes, these membranes exhibit superior flow battery performance. According to the implementation scheme, these membranes enable fully polysulfide-ferrocyanide (S-Fe) redox flow batteries (RFBs) to cycle stably for over 1600 cycles (e.g., >6 months) at 20 mA cm⁻², with high coulombic efficiency (e.g., >99.9%) and low capacity decay rate (e.g., 0.0034% / day). Their cost and performance, and a comparison with state-of-the-art N117 membranes, are shown in Tables 1 and 2 below, respectively. Instruction manual 7 / 21 pages 10 CN 122207122 A

[0092] These membranes can be included in other applications, including but not limited to: iron-chromium RFB systems; basic zinc-iron RFB systems; zinc-manganese RFB systems; tin-based RFB systems; lead-based RFB systems; basic quinone-based RFB systems; non-aqueous RFB systems (where the redox active material is non-oxidizing and non-corrosive); proton exchange membrane fuel cells (PEMFC); nitrate reduction processes; water electrolysis; and gas separation. Table 1: Cost Comparison Table 2: Performance Comparison

[0093] Figures 1A to 1D illustrate different phase separation behaviors for forming ion transport channels. Figure 1A illustrates a polymer self-assembly centralized ion transport channel of Nafion membranes. Commercial Nafion membranes have a hydrophobic backbone (-CF2-) and hydrophilic sulfonic acid groups (-SO3H). Microphase separation can lead to the formation of centralized ion transport channels between polymer chains. Figures 1B to 1D illustrate dispersed ion transport channels regulated by the sulfonate or sulfonic acid portion of a sulfone-based hydrocarbon membrane according to some embodiments of the present invention. The hydrophilic sulfone group (-SO2-) reduces the degree of microphase separation, thereby forming dispersed ion transport channels.

[0094] Figures 2A to 2H illustrate some properties and characterizations of ion-selective membranes according to embodiments. Figure 2A shows a comparison of water / electrolyte absorption rates in three different aqueous solutions (pure water, 1 M KOH aqueous solution, and 1 M KCl aqueous solution) according to the specification, page 8 / 21, 11 CN 122207122 A (e.g., SPES30 has a water absorption rate of 14.2%, while the commercial Nafion N117 has a water absorption rate of 10.7%). Figure 2B shows the swelling rates of the membranes in pure water, 1 M KOH aqueous solution, and 1 M KCl aqueous solution. Embodiments containing sulfone-based hydrocarbon membranes show lower swelling rates than N117. Figure 2C shows the water channel density of the polymer matrix (e.g., SPES30, SPSF30, and SPPSU30 have water channel densities of 0.85 g cm⁻³, 0.76 g cm⁻³, and 0.73 g cm⁻³, respectively, while N117 has 0.70 g cm⁻³). Figure 2D shows the small...Angular X-ray scattering spectra, where the measured values ​​d represent the Bragg spacing for each corresponding case. Figure 2E shows AFM tap-mode phase images of N117 and S30, with the dark areas representing the hydrophilic regions of the polymer matrix. Figure 2F shows the areal resistivity (ASR) of the membranes measured in two different electrolyte solutions (1 M KOH aqueous solution and 1 M KCl aqueous solution) (e.g., the ASR of S30 in 1 M KOH (2.39 cm2) is comparable to that of N117 (2.33 cm2)). Figure 2G shows the permeability of polysulfide ions through each corresponding membrane, with diffusion rates tested at room temperature. Figure 2H shows the mechanical properties of each corresponding membrane, including tensile strength and elongation at break. Embodiments containing sulfone hydrocarbon membranes have higher tensile strengths than Nafion N117 (e.g., tensile strengths of N117 and S30 are 18.8 MPa and 32.2 MPa, respectively).

[0095] Figures 3A to 3D show the electrochemical measurements and cell performance of the membranes according to the embodiments. Figure 3A shows the open-circuit voltage versus time curves for the S30 and N117 films. Figures 3B to 3C show the voltage curves of the S30 and N117 films during charge-discharge cycle tests at a current density of 20 mA cm⁻², respectively. The N117 film exhibited an increase in overpotential and rapid capacity decay within less than 100 cycles, while the S30 film showed high cycle stability with negligible voltage curve changes. Figure 3D shows the battery performance of the S30 film for 1100 hours in a long-term cycle test, and the battery performance of the N117 film before degradation at 250 hours.

[0096] Figures 4A to 4F show how surface modification enhances cycle stability according to embodiments. Figure 4A schematically shows an aqueous polysulfide-ferrocyanide redox flow battery according to one embodiment. Figures 4B to 4D show the voltage curves of the modified films at different current densities from 10 mA cm⁻² to 50 mA cm⁻². Figure 4B shows the galvanostatic voltage curve of the modified Nafion base film. Figure 4C shows the galvanostatic voltage curve of the modified SPES base membrane. Figure 4D shows a comparison of the voltage curves of the modified Nafion base membrane (N117-C) and the SPES base membrane (S30-C) at current densities of 20 mA cm⁻² (solid line) and 50 mA cm⁻² (dashed line). Figure 4E shows an optical photograph of an aqueous polysulfide-ferrocyanide redox flow battery organized according to the schematic structure of Figure 4A according to one embodiment. Figure 4F shows the battery performance curve of the modified SPES base membrane with an energy efficiency recovery program according to one embodiment at a current density of 20 mA cm⁻² for 180 days.

[0097] Figure 5 compares the ion exchange capacity (IEC) of Nafion resin and various sulfonated sulfone hydrocarbon polymers according to the embodiment.

[0098] Figures 6A to 6D are bar graphs of the water / electrolyte absorption rate and swelling rate of the membrane relative to N117 according to some embodiments of the present invention. Figure 6A shows the water / electrolyte absorption rate as a function of membrane composition, while Figure 6B gives the swelling rates of Nafion 117 and sulfonated polyether sulfone (SPES) with different degrees of sulfonation. Figure 6C compares the water / electrolyte absorption rates of Nafion 117, S30, and surface-modified membranes, and Figure 6D compares the swelling rates of Nafion 117, S30, and surface-modified membranes.

[0099] Figures 7A and 7B show digital photographic images of the battery assembly used for EIS testing and the resulting assembled battery, as well as the battery equivalent circuit model used to fit the Nyquist plot of the S10 membrane (Figure 7D).

[0100] Figures 8A to 8F are bar graphs of the area resistivity (ASR) and ionic conductivity of the films according to the embodiments, wherein: 8A shows the ASR of films with different comonomers; 8B shows the ASR of films with different degrees of sulfonation (DS); 8C shows the modified film; 8D shows the ionic conductivity of films with different comonomers; 8E shows the film with different DS; and 8F shows the ionic conductivity of the surface-modified film.

[0101] Figure 9A shows a composite graph of the standard UV-Vis spectra of K2S2 in 1.0 M KOH aqueous solution prepared according to the embodiments for RFB, with increasing K2S2 concentrations, as per specification page 9 / 21, 12 CN 122207122 A, where these spectra show a linear fit between absorbance at 300 nm and concentration. Similarly, Figures 9C to 9D show the UV-Vis absorption spectra of different concentrations of K2S4 in 1.0 M KOH aqueous solution and the linear fit curves of absorbance at 300 nm, respectively. Similarly, Figures 10A to 10D show the spectra and graphs of K4[Fe(CN)6] and K3[Fe(CN)6] in 1.0 M KCl aqueous solution at 323.4 nm and 420.9 nm, respectively, according to some embodiments of the present invention. Figure 10A is the UV-Vis absorption spectrum of K4[Fe(CN)6], and Figure 10C is the UV-Vis absorption spectrum of K3[Fe(CN)6].

[0102] Figures 11A to 11B are graphs showing the difference in S2 2− ion permeability of sulfone-based films with different degrees of sulfonation and similar films with / without surface modification.

[0103] Figures 12A to 12F show SEM images of the S30 membrane surface, where Figure 12A is the SEM image of the S30 membrane surface before immersion, Figure 12B is the SEM image of the S30 membrane surface after immersion in 1 M K2S2-1 M KOH for 40 days, Figure 12C is the SEM image of the S30 membrane surface after immersion in 1 M K2S4-1 M KOH for 40 days, and Figure 12D is the SEM image of the S30 membrane surface after immersion in 0.5 M K4[Fe(CN)6]-1 M KOH for 40 days.Figure 12E shows the SEM image of the S30 membrane surface after soaking in KCl for 40 days. Figure 12F shows the SEM image of the S30 membrane surface after soaking in 0.5 M K3[Fe(CN)6]-1 M KCl for 40 days.

[0104] Figure 13 shows the FTIR spectra of the S30 membrane alone and in the negative and positive electrolytes.

[0105] Figures 14A to 14C are SEM images of the S30-C membrane surface at different magnifications, and Figures 14D to 14F are SEM images of the N117-C membrane surface at different magnifications. Similarly, Figures 15A to 15C are SEM images of the S30-C membrane cross-section at different magnifications, and Figures 15D to 15F are SEM images of the N117-C membrane cross-section at different magnifications. Figures 16A to 16B show SEM images and energy dispersive spectroscopy (EDS) images of the cross-section of the S30-C membrane at one magnification and a higher magnification, respectively.

[0106] Figure 17A is a composite plot of coulombic efficiency (CE) and energy efficiency (EE) of membranes with different comonomers. Figure 17B shows the voltage curves of N117 and various sulfone-based membranes at a current density of 20 mA cm⁻², with the inset being a magnified view of the curves. Figure 17C is a comparison of Nyquist plots of batteries assembled from N117, S30, F30, and P30 from left to right.

[0107] Figures 18A to 18B are battery performance plots of coulombic efficiency (CE) and energy efficiency (EE) as a function of current density for N117 and membranes with different degrees of sulfonation according to embodiments, as well as surface-modified membranes.

[0108] Figure 19 shows an SEM of a polymer matrix membrane structure with a wrinkled or folded structure associated with low Ra (below 7) according to an embodiment of the present invention. The S2 2- ion permeability of the low Ra membrane is greater than 2 × 10-8 cm2 min-1.

[0109] Figures 20A to 20B are digital photographs of coated membranes according to the embodiments, respectively having defects associated with high Ra (greater than 17) and without defects associated with high Ra (greater than 17). The toner loading after water rinsing is less than 0.1 g cm-2.

[0110] Materials and Methods

[0111] All patents, patent applications, provisional applications and publications (including all figures and tables) cited or referenced herein are incorporated herein by reference in their entirety, provided that they do not contradict the express teachings of this specification.

[0112] The following are examples illustrating procedures for carrying out the implementation of the invention. These examples should not be construed as limiting. Unless otherwise stated, all percentages are by weight and all solvent mixing ratios are by volume.

[0113] Example 1 - Design of Dispersed Ion Transport Channels

[0114] To systematically elucidate the key role of polymer structural units and how they affect the connectivity of hydrophilic regions in sulfone-based films, three different comonomers, including bisphenol, hexafluorobisphenol A, and diphenyl sulfone, were investigated. Sulfonated polyphenyl sulfone (SPPSU) exhibits a tight molecular chain arrangement (e.g., the density of dry SPPSU is 1.42 g cm⁻³) due to π-π stacking¹⁹ or the formation of charge-transfer complexes²⁰, resulting in minimal hydrophilic regions within the polymer (e.g., the water cluster diameter of SPPSU (P30), denoted as “d”, is 1.57 nm, as shown in the SAXS of Figure 2D). The hexafluorobisphenol A (“-C(CH3)-”) in sulfonated polysulfone (SPSF) and the diphenyl sulfone (“-SO2-”) in sulfonated polyether sulfone (SPES) have additional electron-rich comonomers (the group solubility parameters (Fdi) of the dispersed components of hexafluorobisphenol A and diphenyl sulfone are 770 J1 / 2cm2 / 3mol-1 and 590 J1 / 2cm2 / 3mol-1, respectively) and undergo active π-flipping motion of the benzene ring (increasing free volume)21, resulting in a relatively loose structure and confining water molecules22. It is worth noting that SPES contains two sulfone groups in one monomer, which enhances the possibility of interaction between the polymer backbone and sulfonic acid groups, thereby promoting more ion transport channels in the polymer matrix (the water channel density of the SPES (sulfonation degree = 30%) membrane is 0.85 g cm⁻³, while the water channel densities of SPSF (sulfonation degree = 30%) and SPPSU (sulfonation degree = 30%) are 0.76 g cm⁻³ and 0.73 g cm⁻³, respectively). As shown in Figure 1C, the comonomer of SPPSU (Figure 1C-1) is bisphenol, while the comonomers of SPSF and SPES are bisphenol A (Figure 1C-2) and diphenyl sulfone (Figure 1C-3), respectively. Among them, -C(CH₃)₂- of SPSF and -SO₂- of SPES provide electron-rich comonomers.

[0115] As shown in Figure 1D, due to the greater number of sulfone groups, SPES has two ion transport channels between two molecules, while SPSF and SPPSU have only one. For membranes of similar size, the water channel density of the membrane is shown in Figure 2C. Water channel density is the increase in water absorption per unit volume, with S30, which has more ion transport channels in the polymer matrix, showing the highest value.

[0116] In addition to the comonomer composition in the main chain, the number of sulfonate groups on the chain, i.e., the degree of sulfonation, is also crucial for the formation of ion transport channels. When the degree of sulfonation of sulfonated hydrocarbon polymers is low (below 10%), their ion exchange capacity (IEC) is shown in Figure 5 for the polymers. The hydrophilic regions in the polymer matrix are independent of each other and form dead-end water channels or water islands 15.It is unlikely to contribute to the transport of ions through an ion-selective membrane. Instead, when there are a large number of sulfonic acid groups (e.g., sulfonation degree > 50%), many small channels form a large channel, which enhances ion transport but weakens ion selectivity.

[0117] A large number of sulfonic acid groups means a high degree of sulfonation, which in this embodiment is, for example, above 50%, as shown in Figure 5, where S50 has the highest IEC. Many small channels mean dispersed ion transport channels in the polymer matrix. The small channels connect and form a large channel, thereby increasing ion transport (ionic conductivity), as shown in Figure 8E. When the ion transport channel is large, polysulfide ions are more likely to cross-permeate, as shown in Figure 11A, where S50 with the highest sulfonation degree has a large ion transport channel, resulting in severe ion permeability.

[0118] To optimize the channel size and distribution, small-angle X-ray scattering (SAXS) showed that the water cluster diameter was less than 1.65 nm, water channel density testing showed a water channel density of 0.7 g cm⁻³ to 0.9 g cm⁻³, and AFM images showed that there were 1 to 3 ion transport channels within a 1 nm² image. The size and distribution of the dispersed ion transport channels were characterized by SAXS and AFM, and the structure-performance-behavior relationships of various sulfonated sulfone-based hydrocarbon polymers with different comonomers and degrees of sulfonation were established. Detailed information and abbreviations for membrane preparation are provided in the Methods section and Table 3. Table 3 Abbreviations and corresponding compositions of membrane samples Specification 11 / 21 pages 14 CN 122207122 A

[0119] Table 3 notes: Thickness represents the thickness of the K+ type wet membrane sample. aSPES: Sulfonated polyether sulfone. bSPSF: Sulfonated polysulfone. cSPPSU: Sulfonated polyphenylene sulfone. dDS: Degree of sulfonation. eDMAC: N,N-dimethylacetamide.

[0120] Example 2 – Evaluation and Characterization of the Membrane

[0121] Ion-selective membranes swell by absorbing water to form narrow, interconnected channels for ion transport. As shown in Figure 2A, sulfone-based membranes exhibit higher water / electrolyte absorption rates than N117 membranes, but as shown in Figure 2B, their swelling rates are lower than those of N117 membranes. In pure water, the water absorption rates of S30 and N117 are 14.2% and 10.7%, respectively. However, the swelling rate of S30 (22.8%) is lower than that of N117 (33.3%). According to some embodiments, sulfone-based membranes reduce phase separation by forming hydrogen bonds with water molecules, resulting in smaller volume expansion, while the rigid phenyl groups restrict the free volume of the molecular chains, improving the dimensional stability of the membrane. Furthermore, the different properties of water / electrolyte absorption rate and swelling ratio (water > 1 M KOH > 1 M KCl) depend on the degree of phase separation of the polymer membrane in the electrolyte aqueous solution.24. Water activity in the electrolyte solution is suppressed, and water molecules need to overcome an energy barrier to enter the interior of the polymer membrane.18 Therefore, as shown in Figure 2C, the sulfone-based membrane has a higher water channel density than N117, which increases the possibility of constructing ion transport channels.

[0122] The size and distribution of the ion transport channels in the membrane were investigated by small-angle X-ray scattering (SAXS) and tapping-mode atomic force microscopy (AFM). According to Bragg's equation 25, the hydrophilic cluster size of N117 is 3.00 nm, while that of the S30 membrane is 1.65 nm, as shown in Figure 2D. In particular, the F30 and P30 membranes exhibit smaller hydrophilic cluster diameters than the S30 membrane. This is because S30 has more hydrophilic regions in the polymer matrix. These regions interconnect to form a larger area, resulting in larger diameter hydrophilic clusters in the membrane. As shown in Figure 2E, the tapping-mode AFM phase image shows the distribution of the ion transport channels in the membrane.26 N117 exhibits a large and concentrated hydrophilic region, while in the S30 membrane, the hydrophilic region is dispersed and small.

[0123] The ion selectivity of the membrane is affected by the performance of the ion transport channels and the overall morphology.27 The S30 membrane has an area resistivity (ASR) comparable to that of N117, for example, in 1 M KOH solution, the ASRs of S30 and N117 are 2.39 cm2 and 2.33 cm2, respectively, as shown in Figure 2F. Due to the lower water channel density, the F30 and P30 membranes exhibit higher ASRs. Thanks to the dispersed ion transport channels, the permeability of the S30 membrane is much lower than that of N117, as shown in Figure 2G, where the permeability of S4 2− ions through N117 is 2.14 × 10−8 cm2 min−1, while this permeability is not detected in the sulfone-based membrane. Although S30 and N117 are comparable in their ability to conduct K+ ions across the membrane, S30 exhibits a much higher ion selectivity than N117 due to its more numerous but smaller ion transport channels.

[0124] Data for K2S2 and K2S4 were collected from two different tests in different solutions. The concentration of polysulfide ions was fixed at 1 mol / L, such as 1 M K2S2 in 1 M KOH and 1 M K2S4 in 1 M KOH. The other side of the membrane was a 1 M KOH aqueous solution, with a solution volume of 7 mL on each side. Concentrations were measured using a UV-Vis spectrophotometer. At low concentrations, ion absorption was linearly related to concentration. Since ion permeation is related to osmotic pressure caused by the concentration gradient, the concentration of S2 ions on the receiving side is expected to remain stable or slow as osmotic pressure decreases.

[0125] The mechanical properties of the membrane in flow battery applications have been evaluated, as shown in Figure 2H. The tensile strength of N117 is 18.8 MPa, while the S30 membrane exhibits superior tensile strength, reaching 32.2 MPa.MPa, and has higher tensile strength than F30 and P30. In addition, Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) confirmed the chemical and thermal stability of the sulfone-based hydrocarbon polymer, as shown in Figure 13. Considering the performance index 28 of the ion-selective membrane for RFB applications, the sulfone-based ion-selective membrane has the high ion selectivity, stability and mechanical strength required for polysulfide-based RFB.

[0126] Example 3 - Battery Performance Evaluation in Flow Batteries

[0127] The application of sulfone-based hydrocarbon membranes with dispersed ion transport channels is illustrated using polysulfide-ferrocyanide (S-Fe) RFB. As shown in Figure 3A, the battery voltage of the S-Fe RFB using the N117 membrane, which forms a centralized ion transport channel through phase separation, rapidly dropped to 0.2 V in 150.2 hours. The S30 membrane exhibited an ultra-low self-discharge rate by suppressing ion cross-permeability through dispersed ion transport channels. Furthermore, as shown in Figures 17A to 17C, the performance of the membrane battery under charge-discharge tests at various current densities shows that the coulombic efficiency (CE > 99.5%) of the sulfone-based membrane is much higher than that of the N117 membrane (CE: 97.1% to 99.2%). Specifically, the energy efficiency of the S30 membrane is better than that of F30 and P30, and comparable to that of N117.

[0128] The long-term cycle stability of the flow battery was measured by charge-discharge tests at a current density of 20 mA cm⁻². As shown in Figure 3C, the N117 membrane showed increasing overpotential and rapid capacity decay with increasing cycle number. In contrast, as shown in Figure 3B, the S30 membrane exhibited excellent cycle stability, with no change in the voltage curve observed. The results show that the CE of the S30 membrane is as high as 99.6%, which is better than that of the N117 membrane (98.8%). Furthermore, as shown in Figure 3D, the cycle life of the flow battery was extended by using the S30 membrane. The battery assembled with the S30 membrane exhibited extremely low capacity decay rate after 1100 hours of long-term cycling operation, at 0.0004% / cycle and 0.0034% / day.

[0129] Example 4 - Applying a membrane to extend the cycle life of a polysulfide-based redox flow battery

[0130] Long-term cycle stability is the most critical bottleneck in the practical application of polysulfide-based RFB systems. This is related to the cross-permeation of polysulfide ions. On the one hand, redox active materials permeate the membrane, leading to irreversible capacity decay29; on the other hand, polysulfide ions are oxidized to elemental sulfur in the positive electrode electrolyte. These insoluble substances deposit inside the ion-selective membrane or on the electrode, resulting in an increase in the battery's internal resistance. The S30 membrane exhibits low polysulfide ion permeability due to its dispersed ion transport channels. However, ion diffusion still exists, and energy efficiency loss gradually accumulates. Surface modification enhances the cycle stability of the membrane. In these embodiments, surface modification that controls swelling alters the morphology of the ion transport channels inside the membrane.The distribution is as described in Example 5 below. As a result, as shown in Figures 4B to 4C, the overpotential of the S30-C membrane is much lower than that of the N117-C membrane. At a current density of 20 mA cm⁻², the overpotential of the flow battery assembled with the S30-C membrane is 171.8 mV, while the overpotential of the flow battery assembled with the N117-C membrane is 248 mV.

[0131] Performance recovery procedures have been extensively studied to extend the lifespan of RFB systems. For example, vanadium redox flow batteries (VRFB) recover capacity loss and energy efficiency decay by electrolyte rebalancing. This energy efficiency (EE) recovery procedure has been introduced into polysulfide-based RFB systems. The battery's energy efficiency decreased from 80.2% to 72.9% after 90 days and was recovered to 78.2% by using an energy efficiency recovery procedure with the original electrolyte. Therefore, the S-Fe flow battery assembled using the S30-C membrane exhibits an ultra-long cycle life (over 180 days) and an average energy efficiency of up to 75.2%.

[0132] Example 5 - Design Specification of Surface Swelling Control Method 13 / 21 pages 16 CN 122207122 A

[0133] Solvents dropped onto the membrane surface cause the polymer to swell and damage the surface structure of the membrane. In addition, the binder (hydrophobic substance) will penetrate into the polymer matrix along with the solvent. When the solvent evaporates, the hydrophobic binder will inhibit the formation of water channels in the polymer matrix, resulting in shrinkage of the ion transport channel size. This not only damages the surface structure of the membrane, but also changes the morphology of the ion transport channels, resulting in differences in ion selectivity and lower ion conductivity.

[0134] A swelling control method for surface modification optimizes solvent treatment by using a solvent with appropriate polarity to ensure that the toner is uniformly distributed in the slurry without severely swelling the polymer and damaging the membrane structure. The coating thickness on one side is approximately 5 μm to 10 μm, and the total thickness is approximately 10 μm to 20 μm. This swelling control method is based on the Hansen solubility parameter (HSP), which takes into account the energy of the solvent to cause the polymer to swell. Both the polymer (SPES30) and the solvent (DMF, DMAC, NMP, acetone, IPA, ethanol, and water, or combinations thereof in a 2 / 3 ratio, one of the advantageous ratios being IPA:water = 7:3) have cohesive energy that can be decomposed into three components: dispersibility, polarity, and hydrogen bonding. The HSP-derived value (Ra) between the polymer and the solvent is determined by using HSP and the following formula: Ra2 = 4(δD1-δD2) 2+(δP1-δP2) 2+(δH1-δH2) 2

[0135] where δD, δP, and δH represent the dispersibility, polarity, and hydrogen bonding parameters of the molecules, respectively. The smaller the Ra value between the polymer and the solvent, the more likely the polymer is to swell.

[0136] The range of Ra should be 7-17. If Ra is too small (e.g., less than 7), it will promote membrane / polymer swelling and damage the membrane structure. If Ra is too large (e.g., greater than 17), the coating may be uneven and may be washed away by water.

[0137] High-performance, low-cost sulfone-based hydrocarbon membranes with dispersed ion transport channels and carbon coatings have resulted in polysulfide-based redox flow batteries. The construction of ion transport channels can be finely controlled through the design of polymer molecules. As confirmed by small-angle X-ray scattering and atomic force microscopy, the water channel density determines the formation and size of ion transport channels. The use of sulfone-based membranes in polysulfide-ferrocyanide redox flow batteries can achieve stable cycling performance with high coulombic efficiency (> 99.6%) and low capacity decay rate (0.0034% / day). Energy efficiency recovery programs can boost the performance of flow batteries to more than 1600 cycles for 180 days.

[0138] Example 6 - Chemicals

[0139] All chemicals were used as received. Potassium polysulfide (K2Sx, ≥42% as K2S, x determined to be approximately 2.0), sulfur powder (sublimed and purified, approximately 100 mesh particle size), N,N-dimethylacetamide (DMAC, ≥99%), 2-propanol (IPA, anhydrous, ≥99.5%), 1-methyl-2-pyrrolidone (NMP, anhydrous, 99.5%), sulfuric acid (H2SO4, 95% to 98%), and hydrogen peroxide (H2O2, 30 wt% aqueous solution) were all purchased from Sigma-Aldrich. Potassium ferrocyanide (K4[Fe(CN)6]·3H2O, ≥99.5%), potassium ferricyanide (K3[Fe(CN)6], ≥99.5%), potassium hydroxide (KOH, 95%), sodium hydroxide (NaOH, 99.7%), potassium chloride (KCl, 99.8%), sodium chloride (NaCl, 99.9%), riboflavin sodium phosphate (FMN-Na, 93%), polytetrafluoroethylene formulation (PTFE, 60 wt% aqueous dispersion), and phenolphthalein (pH indicator) were all purchased from Dieckmann. Sulfonated sulfonate polymers of different degrees of sulfonation, including sulfonated polyethersulfone (SPES), sulfonated polysulfone (SPSF), and sulfonated polyphenylene sulfone (SPPSU), were all purchased from Dech Technology. Polyvinylidene fluoride (PVDF, HSV900) was purchased from Arkema. Nafion membrane (N117, DuPont) was purchased from H2FLOW (Shanghai) Advanced Materials International Trading Co., Ltd. Carbon felt (GFD 4.6EA) was purchased from SGL Carbon SE. Ketjen Black (KB, ECP-600JD) was purchased from Lion Corporation (Japan).

[0140] Example 7 - Membrane Preparation

[0141] All polymer powders were stored in a drying oven. The membrane was prepared by thermally induced phase separation. First, the polymer solution was dissolved in water...The polymer solution was dissolved in DMAC to form a homogeneous solution, and then degassed overnight. The concentration of the casting solution was 30 wt%. The polymer solution was poured onto a clean glass plate and cast with a doctor blade at a speed of 0.12 m min⁻¹, and then dried in a casting coater at 80°C for 8 hours. After that, the membrane was peeled off from the plate and converted to the K-type by immersion in a 1 M KOH aqueous solution. Finally, the membrane was rinsed with deionized water and stored in deionized water. The thickness of the wet membrane was about 150 µm. The Nafion membrane was treated sequentially with 5.0% H₂O₂, 5.0% H₂SO₄ and 1 M KOH for 32 minutes.

[0142] The surface-modified membrane was prepared by drop coating. For sulfonated hydrocarbon membranes, toner, binder (mass ratio of toner to binder was fixed at 8:1) and solvent (4 mL) were mixed and ultrasonically treated for 20 minutes to form a homogeneous slurry. The mass loading of carbon powder on each side of the membrane was approximately 0.23 mg cm⁻². The membrane was dried in an oven at 80°C for 12 hours and then soaked in deionized water for later use. The Nafion-based modified membrane was prepared using methods known in the art and disclosed in previous work.

[0143] Example 8 – Characterization of Polymer and Membrane

[0144] Example 8.1 – Ion Exchange Capacity

[0145] The ion exchange capacity (IEC) was determined by titration. First, the H-type dry membrane was suspended in a saturated NaCl aqueous solution for 24 hours to release H⁺ ions. The solution was titrated with 0.1 M NaOH solution, using phenolphthalein as a pH indicator. The IEC of the polymer was calculated using the following formula:

[0146] Wherein, VNaOH is the volume of NaOH solution (µL) when phenolphthalein turns red; W_dry is the weight of the dry membrane (mg).

[0147] Example 8.2 – Water / Electrolyte Absorption Rate and Swelling Rate

[0148] The K-type sample membrane was completely dried in a vacuum oven at 80°C for 24 hours to form a dehydrated membrane. The dehydrated membrane was then immersed in deionized water or a salt solution at room temperature for 24 hours to form a hydrated membrane. The water / electrolyte absorption rate (ω) was determined by the ratio of the mass change to the weight of the dehydrated membrane:

[0149] where mh and md are the weights of the hydrated membrane and the dehydrated membrane, respectively.

[0150] The swelling rate (ω) was calculated by the ratio of the volume change to the volume of the dehydrated membrane:

[0151] where Vh and Vd are the volumes of the hydrated membrane and the dehydrated membrane, respectively. The length, width, and thickness of the membrane were measured using a micrometer.

[0152] The water channel density (ρ) is defined as the ratio of the change in mass to the change in volume of the membrane in pure water:

[0153] Example 8.3—Mechanical Properties

[0154] The mechanical properties of the K-type wet membrane were tested on an electronic universal testing machine (INSTRON 3367). The sample membrane size was 1 cm × 3 cm.cm. The tensile strength and elongation of the membrane were obtained by stress-strain curves.

[0155] Example 8.4 - Morphology

[0156] Scanning electron microscopy (SEM) images were observed using a Quanta 400F. Cross-sections were observed after the membrane was frozen and fractured in liquid nitrogen. The sample was pre-sprayed with platinum powder for 60 seconds. Tapping mode atomic force microscopy (AFM) images were obtained using a Bruker Dimension Icon. The scanning range was 400 × 400 nm.

[0157] Example 8.5 - SAXS and Contact Angle

[0158] Small angle X-ray scattering was tested on a Xenocs Xeuss 2.0 using a detector (Pilatus 3R specification 15 / 21 pages 18 CN 122207122 A 300K) with an X-ray wavelength λ = 1.54 Å. The distance between the sample and the detector was fixed at 538 mm. The water cluster size was calculated according to Bragg's Law 24. Water contact angle was measured by Dataphysics OCA to analyze the hydrophilicity of the membrane surface.

[0159] Example 8.6 - Area resistivity and permeability

[0160] Resistance was measured by electrochemical impedance spectroscopy (EIS) of a static cell with the sample membrane assembled. The frequency range was 0.2 MHz to 0.1 Hz. Area resistivity (ASR) was calculated by the following formula: ASR = A × (Rw - Ro), where A is the effective area of ​​the membrane, and Rw and Ro are the resistances of the cell with or without the membrane, respectively. The membrane sample was pre-soaked in the test solution for 24 hours.

[0161] Ion permeability was tested by clamping the membrane sample in an H-type cell. For polysulfide ions, the feed side was 1 M K2S2 or 1 M K2S4 dissolved in 1 M KOH solution, while the permeate side was filled with 1 M KOH. For ferrocyanide and ferricyanide ions, the feed side and the permeate side were respectively 0.5 M K4 [Fe(CN)6] dissolved in 1 M KCl or 0.5 M K3 [Fe(CN)6] dissolved in 1 M KCl. The solution volumes on both sides of the half-cell were fixed at 8 mL. The absorbance of different ions was collected at room temperature using a UV-Vis spectrophotometer (ASL SEC2020). The permeation coefficient (D) was calculated using the following formula:

[0162] where cf and cp(t) are the ion concentrations on the feed side and the permeate side, respectively; Vp is the solution volume on the permeate side; A and L are the effective area and thickness of the membrane sample.

[0163] Example 8.7 - Chemical Stability

[0164] The K-type membrane sample was stored in an electrolyte solution at room temperature for 40 days 34, 35, after which the electrolyte was washed away with deionized water and dried at 80°C for 24 hours. Fourier transform infrared spectroscopy (FTIR, ThermoFisher) was used in the range of 500 cm⁻¹ to 4000 cm⁻¹.The chemical stability of the membrane was evaluated within the cm⁻¹ range.

[0165] Example 8.8 – Battery Assembly and Testing

[0166] The flow battery consisted of a membrane, a pretreated graphite felt (geometric area 2 × 2 cm²) 36, a polyether ether ketone (PEEK) frame, a graphite plate with a flow field, and a current collector. For the base membrane, porous glass fiber was sandwiched between the positive electrode and the membrane. The positive electrode electrolyte was prepared by 0.5 M K₄[Fe(CN)₆] and 1 M KCl as a supporting electrolyte, while the negative electrode electrolyte was prepared by 1 M K₂S₄ dissolved in 1 M KOH solution and 50 mM FMN-Na as a molecular catalyst. All electrolytes were dissolved in deoxygenated deionized water under argon protection, with a solution volume of 10 mL. The flow battery was tested at a flow rate of 50 mL min⁻¹ in an atmospheric environment.

[0167] Charge and discharge measurement data were collected using the LAND battery testing system. The charging program's cutoff voltage was set to 1.3 V (10 mA cm⁻² to 30 mA cm⁻²), 1.4 V (40 mA cm⁻²), or 1.5 V (50 mA cm⁻²), and the discharging program's cutoff voltage was set to 0.2 V. Long-cycle testing was conducted at a current density of 20 mA cm⁻² and a cutoff voltage of 1.3 V to 0.2 V (1.2 V to 0.2 V after 3000 hours).

[0168] For the energy efficiency (EE) recovery program 37, the positive and negative electrolytes were collected and stored in a glove box. The positive electrolyte reservoir was replaced with 10 mL of a 1 M K₂S₂ solution dissolved in 1 M KOH and circulated for 3 hours using a peristaltic pump. Afterward, the positive electrode was rinsed with 50 mL of deionized water to remove the electrolyte. The battery was not disassembled during this process. After the recovery program, cycle testing was performed using the original electrolyte.

[0169] It should be understood that the embodiments and implementations described herein are for illustrative purposes only, and those skilled in the art will conceive of various modifications or alterations based thereon, which should be included within the spirit and scope of this application and the scope of the appended claims. Furthermore, any element or limitation of any invention or implementation thereof disclosed herein may be combined with any and / or all other elements or limitations (alone or in any combination) of the specification disclosed herein (pages 16 / 21, CN 122207122 A) or any other invention or implementation thereof, and all such combinations are considered within the scope of this invention without limitation.

[0170] The transitional terms “comprising,” “comprises,” or “comprise” are inclusive or open-ended and do not exclude additional, unlisted elements or method steps. In contrast, the transitional phrase “consisting” is more appropriate.The phrase “consisting essentially of” excludes any element, step, or component not specified in the claim. The phrase “consisting essentially of” or “consists essentially of” indicates that the claim covers embodiments that include the specified material or step, as well as those embodiments that do not materially affect the essential and novel features of the claim. The use of the term “comprising / including” considers other embodiments that are “composed of” or “essentially composed of” the components.

[0171] When ranges are used herein, such as dose ranges, combinations of ranges, and sub-combinations (e.g., sub-ranges within the disclosed ranges), they are intended to specify the particular embodiments included therein. When the term “about” is used herein in conjunction with a numerical value, it should be understood that the numerical value may be in the range of 95% to 105% of the numerical value, i.e., the numerical value may be in the range of ±5% of the numerical value. For example, “about 1 kg” means 0.95 kg to 1.05 kg.

[0172] Exemplary Embodiments

[0173] Embodiment 1. A polysulfide-based redox flow battery includes: a sulfonated sulfone-based hydrocarbon membrane having a plurality of dispersed ion transport channels.

[0174] Embodiment 2. The battery according to Embodiment 1, wherein the sulfonated sulfone-based hydrocarbon membrane comprises at least one polysulfone selected from: sulfonated polyether sulfone (SPES), sulfonated polysulfone (SPSF), sulfonated polyphenylene sulfone (SPPSU), sulfonated polyarylene sulfide sulfone (SPSS), and sulfonated polyarylene ether sulfone (SPAES).

[0175] Embodiment 3. The battery according to Embodiment 2, wherein the polysulfone has a rigid hydrophobic aromatic polymer backbone comprising a plurality of aromatic rings, each ring comprising a plurality of hydrogen atoms.

[0176] Embodiment 4. The battery according to Embodiment 3, wherein at least one sulfonate or sulfonic acid group replaces any hydrogen atom on any aromatic ring in the rigid hydrophobic aromatic polymer backbone.

[0177] Embodiment 5. The battery according to Embodiment 2, wherein the degree of sulfonation of at least one polysulfone is at least about 10%.

[0178] Embodiment 6. The battery according to Embodiment 2, wherein the degree of sulfonation of at least one polysulfone is at least about 30%.

[0179] Embodiment 7. The battery according to Embodiment 2, wherein the degree of sulfonation of at least one polysulfone is at least about 50%.

[0180] Embodiment 8. The battery according to Embodiment 1, wherein the sulfonated sulfone-based hydrocarbon film includes a surface modification that effectively controls the swelling of the sulfone-based hydrocarbon film.

[0181] Embodiment 9. The battery according to Embodiment 8, wherein the surface modification includes a carbon coating.

[0182] Embodiment 10. The battery according to Embodiment 1, wherein the thickness of the sulfone-based hydrocarbon film is less than 190 μm.

[0183] Embodiment 11.A sulfonated sulfone-based hydrocarbon membrane for redox flow batteries includes:

[0184] sulfonated polyether sulfone (SPES) having a sulfonation degree of about 30% and a thickness of about 150 μm, wherein the sulfonated hydrocarbon membrane has multiple dispersed ion transport channels with a water channel density of about 0.85 g cm⁻³, an average of about 3 hydrophilic ion transport channels per square nanometer, and a water cluster diameter of about 1.65 nm. Thus, the sulfonated sulfone-based hydrocarbon membrane exhibits the following characteristics: a water / electrolyte absorption rate of about 14% in water, a water / electrolyte absorption rate of about 13% in 1 M KOH, and a water / electrolyte absorption rate of about 12% in KCl aqueous solution; a swelling rate of about 23% in water, a swelling rate of about 19% in KOH, and a swelling rate of about 19% in 1 M KCl aqueous solution; a tensile strength of about 32 MPa and an elongation at break of about 200%.

[0185] Embodiment 12. The sulfonated sulfone hydrocarbon membrane according to Embodiment 11 further includes a carbon coating having a thickness of about 10 μm on each side of the membrane specification page 17 / 21, 20 CN 122207122 A, and a carbon loading of about 0.23 mg cm⁻². The carbon coating is formed from a slurry containing about 50 mg carbon (KB), about 6 mg PTFE, and isopropanol (IPA):water in a volume ratio of about 7:3.

[0186] Embodiment 13. A polysulfide-ferrocyanide redox flow battery, comprising:

[0187] a sulfonated polyethersulfone (SPES) membrane as defined in Embodiment 11;

[0188] a positive electrode electrolyte comprising 0.5 M K4[Fe(CN)6] and 1 M KCl as a supporting electrolyte; and

[0189] a negative electrode electrolyte comprising 1 M K2S4 dissolved in 1 M KOH solution and 50 mM FMN-Na as a molecular catalyst;

[0190] thereby the polysulfide-ferrocyanide redox flow battery exhibits:

[0191] a coulombic efficiency (CE) of at least about 99.4%,

[0192] an energy efficiency (EE) of at least about 83.1% at a current density of about 20 mA cm⁻²;

[0193] a cycle life of more than 1000 hours; and

[0194] Below approximately 0.0004% / cycle or below approximately 0.0034% / day capacity decay rate.

[0195] Embodiment 14. A polysulfide-ferrocyanide redox flow battery according to Embodiment 13, wherein the sulfonated polyethersulfone (SPES) membrane further comprises a carbon coating having a thickness of approximately 10 μm on each side of the membrane and a carbon loading of approximately 0.23 mg cm⁻², wherein the battery exhibits:

[0196] at least approximately 99.9% coulombic efficiency (CE);

[0197] at approximately 20 mAAt a current density of cm⁻², at least about 82.2% energy efficiency (EE);

[0198] a cycle life greater than about 6 months; and

[0199] a capacity decay rate less than about 0.0004% / cycle or less than about 0.0032% / day.

[0200] Embodiment 15. A method for preparing a sulfonated sulfone-based hydrocarbon membrane for a redox flow battery, comprising:

[0201] drying sulfonated polyether sulfone (SPES) polymer powder at about 50°C to prepare dried SPES powder;

[0202] dissolving the dried SPES polymer powder in N,N-dimethylacetamide to form a 30 wt.% SPES casting solution at a temperature of about 25°C;

[0203] degassing the SPES casting solution;

[0204] pouring the SPES casting solution onto a flat plate at a temperature of about 25°C and a relative humidity of less than 25%;

[0205] scraping the solution with a doctor blade at a speed of about 0.12 m min⁻¹ to form a wet film with a thickness of about 800 μm;

[0206] drying the wet film at about 80°C for at least about 8 hours to form a dried sulfonated sulfone-based hydrocarbon membrane with a thickness of about 150 μm;

[0207] The dried sulfonated sulfonated hydrocarbon membrane is peeled off from the plate; and

[0208] The dried sulfonated sulfonated hydrocarbon membrane is immersed in deionized water (DI) to form a wet sulfonated sulfonated hydrocarbon membrane.

[0209] Embodiment 16. The method according to Embodiment 15 further includes:

[0210] immersing a wet sulfonyl hydrocarbon membrane in a 5 wt.% aqueous solution of H2SO4 at about 80°C for at least 1 hour;

[0211] cooling the sulfonyl hydrocarbon membrane to about 25°C;

[0212] washing the sulfonyl hydrocarbon membrane with deionized water, and then immersing it in deionized water at about 25°C for at least 1 hour;

[0213] immersing the sulfonyl hydrocarbon membrane in a 1 M KOH aqueous solution at about 80°C for at least 2 hours;

[0214] cooling the sulfonyl hydrocarbon membrane a second time to about 25°C;

[0215] washing the sulfonyl hydrocarbon membrane again with deionized water, and then immersing it in deionized water at about 25°C for at least 1 hour to obtain a sulfonyl hydrocarbon membrane with a final thickness of about 150 μm to about 155 μm; and the specification, pages 18 / 21, 21 CN. 122207122 A

[0216] The sulfonated sulfone hydrocarbon membrane is soaked in deionized water before use.

[0217] Embodiment 17. The method according to Embodiment 19 further includes:

[0218] wiping the sulfonated sulfone hydrocarbon membrane to remove excess liquid;

[0219] sandwiching the sulfonated sulfone hydrocarbon membrane between two PTFE gaskets;

[0220] providing a carbon-containing slurry, wherein each 50 mg of carbon (KB) corresponds to 0.15 mL of 5% PTFE dispersion, 3.5

[0221] Mix the carbon-containing slurry with 1.5 mL of IPA and 1.5 mL of deionized water;

[0222] Mix the carbon-containing slurry and sonicate for at least about 20 minutes while cooling with ice water;

[0222] Coat each side of the sulfonated sulfone hydrocarbon membrane with the carbon-containing slurry;

[0223] Heat-dry the sulfonated sulfone hydrocarbon membrane, gasket and slurry in an oven at about 80°C for at least 12 hours; and

[0224] Immerse the sulfonated sulfone hydrocarbon membrane in deionized water for at least 24 hours.

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[0262] 37 Saraidaridis , J .&Yang , Z . Electrolyte Takeover Strategy for Performance Recovery in Polysulfide-Permanganate Flow Batteries. Journal of the Electrochemical Society 168, 110556 (2021). Specification 21 / 21 pages 24 CN 122207122 A Figure 1A Figure 1B Specification Figure 1 / 41 pages 25 CN 122207122 A Figure 1C Figure 1D Specification Figure 2 / 41 pages 26 CN 122207122 A Figure 2A Figure 2B Specification Figure 3 / 41 pages 27 CN 122207122 A Figure 2C Figure 2D Specification Figure 4 / 41 pages 28 CN 122207122 A Figure 2E Figure 2F Specification Figure 5 / 41 pages 29 CN 122207122 AFigure 2G Figure 2H Appendix 6 / 41 Page 30 CN 122207122 A Figure 3A Figure 3B Appendix 7 / 41 Page 31 CN 122207122 A Figure 3C Appendix 8 / 41 Page 32 CN 122207122 A Figure 3D Appendix 9 / 41 Page 33 CN 122207122 A Figure 4A Figure 4B Appendix 10 / 41 Page 34 CN 122207122 A Figure 4C Figure 4D Appendix 11 / 41 Page 35 CN 122207122 A Figure 4E Appendix 12 / 41 Page 36 CN 122207122 A Figure 4F Appendix 13 / 41 Page 37 CN 122207122 A Figure 5 Figure 6A Appendix 14 / 41 Page 38 CN 122207122 A Figure 6B Figure 6C Appendix to the Instruction Manual, Page 39, CN 122207122 A Figure 6D Figure 7A Appendix to the Instruction Manual, Page 40, CN 122207122 A Figure 7B Figure 7C Appendix to the Instruction Manual, Page 41, CN 122207122 A Figure 7D Figure 8A Appendix to the Instruction Manual, Page 42, CN 122207122 A Figure 8B Figure 8C Appendix to the Instruction Manual, Page 43, CN 122207122 A Figure 8D Figure 8E Appendix to the Instruction Manual, Page 44, CN 122207122 A Figure 8F Figure 9A Appendix to the Instruction Manual, Page 45, CN 122207122 A Figure 9B Figure 9C Appendix to the Instruction Manual, Page 46, CN 122207122 A Figure 9D Figure 10A Instruction manual figures 23 / 41, page 47, CN 122207122 A, Figure 10B, Figure 10C; Instruction manual figures 24 / 41, page 48, CN 122207122 A, Figure 10D, Figure 11A; Instruction manual figures 25 / 41, page 49, CN 122207122 A, Figure 11B, Figure 12A; Instruction manual figures 26 / 41, page 50, CN 122207122 A, Figure 12B, Figure 12C; Instruction manual figures 27 / 41, page 51, CN 122207122 A, Figure 12D, Figure 12E; Instruction manual figures 28 / 41, page 52, CN 122207122Figure 12F Figure 13 Instruction Manual Drawings 29 / 41 Page 53 CN 122207122 A Figure 14A Figure 14B Instruction Manual Drawings 30 / 41 Page 54 CN 122207122 A Figure 14C Figure 14D Instruction Manual Drawings 31 / 41 Page 55 CN 122207122 A Figure 14E Figure 14F Instruction Manual Drawings 32 / 41 Page 56 CN 122207122 A Figure 15A Figure 15B Instruction Manual Drawings 33 / 41 Page 57 CN 122207122 A Figure 15C Figure 15D Instruction Manual Drawings 34 / 41 Page 58 CN 122207122 A Figure 15E Figure 15F Instruction Manual Drawings 35 / 41 Page 59 CN 122207122 A Figure 16A Instruction Manual Drawings 36 / 41 Page 60 CN 122207122 A Figure 16B Figure 17A Appendix to the Instruction Manual, Page 37 / 41, 61 CN 122207122 A Figure 17B Figure 17C Appendix to the Instruction Manual, Page 38 / 41, 62 CN 122207122 A Figure 18A Figure 18B Appendix to the Instruction Manual, Page 39 / 41, 63 CN 122207122 A Figure 19 Figure 20A Appendix to the Instruction Manual, Page 40 / 41, 64 CN 122207122 A Figure 20B Appendix to the Instruction Manual, Page 41 / 41, 65 CN 122207122 A

Claims

1. A polysulfide-based redox flow battery, comprising: A sulfonated sulfone-based hydrocarbon membrane having multiple dispersed ion transport channels.

2. The battery according to claim 1, wherein the sulfonated sulfone-based hydrocarbon membrane comprises at least one polysulfone selected from the following: sulfonated polyether sulfone (SPES), sulfonated polysulfone (SPSF), sulfonated polyphenylene sulfone (SPPSU), sulfonated polyarylene sulfide sulfone (SPSS), and sulfonated polyarylene sulfone (SPAES).

3. The battery according to claim 2, wherein the polysulfone has a rigid hydrophobic aromatic polymer backbone, the backbone comprising a plurality of aromatic rings, each ring comprising a plurality of hydrogen atoms.

4. The battery according to claim 3, wherein at least one sulfonate group or sulfonic acid group replaces any hydrogen atom on any aromatic ring in the rigid hydrophobic aromatic polymer backbone.

5. The battery according to claim 2, wherein the degree of sulfonation of at least one polysulfone is at least about 10%.

6. The battery according to claim 2, wherein the degree of sulfonation of at least one polysulfone is at least about 30%.

7. The battery according to claim 2, wherein the degree of sulfonation of at least one polysulfone is at least about 50%.

8. The battery according to claim 1, wherein the sulfonated sulfone hydrocarbon film comprises a surface modification that effectively controls the swelling of the sulfone hydrocarbon film.

9. The battery of claim 8, wherein the surface modification comprises a carbon coating.

10. The battery according to claim 1, wherein the thickness of the sulfone-based hydrocarbon film is less than 190 μm.

11. A sulfonyl sulfone-based hydrocarbon membrane for use in a redox flow battery, comprising: Sulfonated polyether sulfone (SPES), wherein the degree of sulfonation of SPES is about 30% and the thickness is about 150 μm, wherein the sulfone-based hydrocarbon membrane has multiple dispersed ion transport channels, and the water channel density of the dispersed ion transport channels is about 0.85 g cm⁻¹. -3 The membrane has an average of about 3 hydrophilic ion transport channels per square nanometer, and the water cluster diameter is about 1.65 nm. As a result, the sulfonyl hydrocarbon membrane exhibits the following characteristics: water / electrolyte absorption rate of about 14% in water, about 13% in 1 M KOH, and about 12% in KCl aqueous solution; swelling rate of about 23% in water, about 19% in KOH, and about 19% in 1 M KCl aqueous solution; tensile strength of about 32 MPa; and elongation at break of about 200%.

12. The sulfonyl sulfone hydrocarbon membrane according to claim 11, further comprising a carbon coating having a thickness of about 10 μm on each side of the membrane and a carbon loading of about 0.23 mg cm⁻¹. -2 The carbon coating is formed from a slurry containing about 50 mg of carbon (KB), about 6 mg of PTFE, and isopropanol (IPA):water in a volume ratio of about 7:

3.

13. A polysulfide-ferrocyanide redox flow battery, comprising: The sulfonated polyether sulfone (SPES) film as defined in claim 11; The positive electrode electrolyte comprises 0.5 M K4[Fe(CN)6] and 1 M KCl as a supporting electrolyte; as well as The negative electrode electrolyte comprises 1 M K2S4 dissolved in 1 M KOH solution and 50 mM FMN-Na as a molecular catalyst. Therefore, the polysulfide-ferrocyanide redox flow cell exhibits the following characteristics: At least approximately 99.4% coulomb efficiency (CE). At approximately 20 mA cm -2 At current densities, the energy efficiency (EE) is at least approximately 83.1%. Cycle life greater than 1000 hours; and Below approximately 0.0004% per cycle or below approximately 0.0034% per day of capacity decay.

14. The polysulfide-ferrocyanide redox flow battery of claim 13, wherein the sulfonated polyethersulfone (SPES) membrane further comprises a carbon coating having a thickness of about 10 μm on each side of the membrane and a carbon loading of about 0.23 mg cm⁻¹. -2 The battery exhibits the following characteristics: At least approximately 99.9% coulombic efficiency (CE); At approximately 20 mA cm -2 At current densities, the energy efficiency (EE) is at least about 82.2%. A cycle life greater than approximately 6 months; and Below approximately 0.0004% per cycle or below approximately 0.0032% per day of capacity decay.

15. A method for preparing a sulfonyl sulfone-based hydrocarbon membrane for redox flow batteries, comprising: Sulfonated polyether sulfone (SPES) polymer powder was dried at about 50°C to prepare dried SPES powder. The dried SPES polymer powder was dissolved in N,N-dimethylacetamide to form a 30 wt.% SPES casting solution at a temperature of about 25°C. The SPES casting solution was degassed. Pour the SPES casting solution onto a plate at a temperature of approximately 25°C and a relative humidity of less than 25%. Use a scraper to apply approximately 0.12 mm of pressure. -1 The coating is applied at a speed of [speed] to form a wet film with a thickness of approximately 800 μm; The wet film is dried at about 80°C for at least about 8 hours to form a dry sulfonated sulfone hydrocarbon film with a thickness of about 150 μm; Peel the dried sulfonyl hydrocarbon film off the plate; and The dried sulfonated sulfonyl hydrocarbon membrane is immersed in deionized water (DI water) to form a wet sulfonated sulfonyl hydrocarbon membrane.

16. The method of claim 15, further comprising: The wet sulfonyl hydrocarbon membrane was immersed in a 5 wt.% H2SO4 aqueous solution at about 80°C for at least 1 hour. The sulfonated sulfone hydrocarbon film was cooled to approximately 25°C. Wash the sulfonyl hydrocarbon membrane with deionized water, and then soak it in deionized water at about 25°C for at least 1 hour; The sulfonated sulfone hydrocarbon membrane was immersed in a 1 M KOH aqueous solution at approximately 80°C for at least 2 hours. The sulfonated sulfone hydrocarbon membrane was cooled a second time to approximately 25°C; The sulfonated sulfone hydrocarbon membrane was washed again with deionized water and then soaked in deionized water at about 25°C for at least 1 hour to obtain a sulfonated sulfone hydrocarbon membrane with a final thickness of about 150 μm to about 155 μm. as well as Before use, soak the sulfonated sulfone hydrocarbon membrane in deionized water.

17. The method of claim 15, further comprising: Wipe the sulfonyl hydrocarbon membrane to remove excess liquid; Sulfonated sulfone hydrocarbon membrane is sandwiched between two PTFE gaskets; A carbon-containing slurry is provided, wherein for every 50 mg of carbon (KB), there is 0.15 mL of 5% PTFE dispersion, 3.5 mL of IPA, and 1.5 mL of deionized water. The carbon-containing slurry is mixed and ultrasonically treated for at least about 20 minutes, while being cooled with ice water; A carbon-containing slurry is coated on each side of a sulfonyl hydrocarbon membrane; Sulfonated sulfone hydrocarbon films, gaskets, and slurries are heated and dried in an oven at approximately 80°C for at least 12 hours. as well as Immerse the sulfonated sulfone hydrocarbon membrane in deionized water for at least 24 hours.

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