Sulfur Iodine Research Articles

Unlocking Interfacial Interactions of In Situ Grown Multidimensional Bismuth‐Based Perovskite Heterostructures for Photocatalytic Hydrogen Evolution

AbstractTo combat the energy crisis and environmental pollution, developing renewable energy technology such as hydrogen (H2) production is necessary. The sulfur–iodine thermochemical cycle has high commercial potential in conducting hydrogen iodide (HI) splitting for H2 generation, but it requires high‐temperature conditions. In comparison, photocatalytic HI splitting of halide perovskites is non‐polluted and low‐cost for H2 production at room temperature. Herein, an in situ constructed multidimensional bismuth (Bi)‐based 3D/2D EDABiI5/MA3Bi2I9 perovskite heterojunction is developed first by synergistically integrating dimensionality control with heterostructure engineering. Accordingly, the optimal EDABiI5/MA3Bi2I9 without any co‐catalysts exhibits the H2 evolution rate of 213.63 µmol h−1g−1 under irradiation. Equally importantly, interfacial dynamics of solid/solid and solid/liquid interfaces play a crucial role in photocatalytic performance. Therefore, using temperature‐dependent transient photoluminescence and electrochemical voltammetric techniques, it is confirmed that the exciton transportation of EDABiI5/MA3Bi2I9 is accelerated by stronger electronic coupling arising from an enhanced overlap of electronic wavefunctions. Moreover, the effective diffusion coefficient and electron transfer rate of EDABiI5/MA3Bi2I9 demonstrate efficient heterogeneous electron transfer, resulting in improved photocatalytic hydrogen production. Consequently, the in situ formation of perovskite heterostructures studied by a combination of photophysical and electrochemical techniques provides new insights into green hydrogen evolution and interfacial interaction dynamics for commercial applications of solar‐to‐fuel technology.

Experimental Study of the Characteristics of HI Distillation in the Thermochemical Iodine–Sulfur Cycle for Hydrogen Production

Experimental Study of the Characteristics of HI Distillation in the Thermochemical Iodine–Sulfur Cycle for Hydrogen Production

Integrated scheme analysis and thermodynamic performance study of advanced nuclear-driven hydrogen-electricity co-production systems with iodine-sulfur cycle and combined cycle

A promising method for massive clean hydrogen production is the Very High Temperature Reactor (VHTR)-driven Nuclear Hydrogen Production (NHP) system using the Iodine–Sulfur (IS) cycle. Research on integrated scheme and thermodynamic performance of the VHTR-driven NHP system using the IS cycle has, however, received little attention up to this point, particularly when the combined cycle is employed as the power generation cycle. In order to bridge this research gap, this work proposed and studied two distinct VHTR-driven hydrogen-electricity co-production systems with the IS cycle and combined cycle: the independent operating system and the coupled operating system. Thermodynamics was used to model these two systems, and system thermodynamic performance was examined under the baseline operating conditions. A parametric study was further conducted on how two important operating parameters affected system thermodynamic performance. The primary findings indicated that the coupled operating system outperformed the independent operating system in terms of thermodynamic performance. Additionally, both the independent and coupled operating systems could produce hydrogen at the same rate of 289.8 mol/s, with net electrical power outputs of 61.07 MW and 102.7 MW, respectively, under the baseline operating conditions. Furthermore, it was discovered that a rise in the mass flow ratio for both operating systems would result in a notable reduction in system efficiency.

Multi‐Point Collaborative Passivation of Surface Defects for Efficient and Stable Perovskite Solar Cells

AbstractThe inherent defects (lead iodide inversion and iodine vacancy) in perovskites cause non‐radiative recombination and there is also ion migration, decreasing the efficiency and stability of perovskite devices. Eliminating these inherent defects is critical for achieving high‐efficiency perovskite solar cells. Herein, an organic molecule with multiple active sites (4,7‐bromo‐5,6‐fluoro‐2,1,3‐phenylpropyl thiadiazole, M4) is introduced to modify the upper interface of perovskites. When M4 interacts with the perovskite surface, the active bromine (Br) site interacts with lead (Pb) at the surface to repair iodine atomic vacancy defects. The fluorine (F) site of M4 interacts with Pb to correct octahedral crystal lattice distortions and eliminate PbI defects. Additionally, sulfur–iodine (S–I) interactions reduce I–I dimerization and eliminate IPb defects. It is also calculated that the energy level of M4 aligns with the band gap, promoting charge transfer. As a result, the perovskite devices achieve an efficiency of 25.1%, a stabilized power output (SPO) of 25.0%, a voltage of 1.19 V, and a fill factor of 85.2%. The device retains 95% of its initial efficiency after 2000 h of ageing in a nitrogen atmosphere. Thus, multi‐point cooperative passivation of surface defects provides an effective method to improve the efficiency and stability of perovskite solar cells.

Developing an online composition prediction for an HI–I2–H2O system using deep neural network

We developed a deep neural network (DNN) method to predict the composition of the HI–I2–H2O system in the iodine–sulfur (IS) process of thermochemical water-splitting hydrogen production using measurable properties. Unlike conventional titration analysis, this approach allows for a quick understanding of fluid composition, providing essential information for controlling operating conditions. This study focused on the HI–I2–H2O three-component system within the IS process. Gibbs’ phase rule was used to construct the DNN model using online measurement parameters, such as temperature, pressure, and density, as input conditions. The model was trained with experimental data, and the structural parameters were tuned. Composition prediction using actual trend data correlated well with titration analysis measurements. The local interpretable model-agnostic explanations method was incorporated to acquire insights into the significance of input parameters for compositions from the DNN model, providing valuable information on crucial parameters for effective composition control.

Ta–W metal alloy membrane reactor for HI decomposition in I–S thermochemical cycle for hydrogen production

HIx processing section of Iodine-Sulfur (IS) thermochemical cycle suffers from the drawbacks of highly corrosive environment and a low thermodynamic conversion of HI decomposition (∼22% at 450 °C). This study investigates, for the first time, the potential of tantalum-tungsten (Ta–W) metal alloy membrane reactor for the decomposition of HI. A thin film of Ta–W alloy was deposited on clay-alumina support by DC magnetron sputtering under optimized set of parameters. The corrosion resistance of the Ta–W membrane was evaluated through electrochemical corrosion studies and immersion coupon tests in azeotropic HI (57 wt % in water) environment. The results confirmed that Ta–W had a higher corrosion resistance than Ta. HI decomposition was carried out in Ta–W membrane reactor and suitable operating parameters were finalized. An enhanced conversion of ∼98% was obtained at 450 °C and 105 Pa, while no permeation of HI, water and iodine was observed across the membrane.

Experimental investigations of hydrogen iodide (HI) decomposition process for different catalysts and various temperature conditions

This article presents the results of experimental work carried out at the Institute of Power Engineering on the process of thermal decomposition of hydrogen iodide. This process is one of the three key steps taking place in sulfur-iodine (S-I) thermochemical hydrogen production technology. For this purpose, a laboratory test rig equipped with an electrically heated chemical reactor was constructed, enabling the study of hydrogen iodide decomposition under controlled conditions. The research was carried out using various catalytic substances, as well as different temperature conditions. The process of hydrogen iodide decomposition required keeping the temperature of the reactor above 300°C and continuous analysis of the concentration of hydrogen formed over time. The results of the study will make it possible to determine the kinetics of the hydrogen iodide decomposition reaction under selected conditions of the process, allowing for future optimization of the process with the use of numerical methods.

Techno-Economic Analysis of Heat-Assisted Hydrogen Production from Nuclear Power

To play a full role in decarbonisation, hydrogen must be produced economically at scale; the role of nuclear power is interesting to national governments as it is capable of supplying both low-carbon electricity and high-quality heat. Depending on the hydrogen production technology choice, a plant may require electricity and/or heat input. This techno-economic evaluation considers not only the costs of the hydrogen plant itself but also the costs of the power supply it requires. This paper calculates cost estimates for HTSE (High Temperature Steam Electrolysis) coupled with nuclear heat and electricity, and a thermochemical SI (Sulphur Iodine) cycle coupled with nuclear heat, based on the predictions of technical process models. These estimates are then compared to estimates made elsewhere for the costs of using wind with low temperature liquid water electrolysis, and steam methane reformation with carbon capture. This analysis led to the identification of the conditions under which nuclear-heat-coupled hydrogen production would be competitively priced. Estimates for nuclear-coupled LCOH2 (levelised cost of hydrogen) in 2050 range from 2.14 to 1.24 £/kg for HTSE, and from 2.88 to 0.89 £/kg for the SI cycle. There is still a great deal of uncertainty around the efficiency of SI and how it may improve over time, and this limits the accuracy to which the LCOH2 can be predicted.

Continuous multiphase Bunsen reactor of iodine-sulfur thermochemical water splitting cycles for hydrogen production: Experimental, Modelling and Design Insights

Thermochemical water splitting cycles (TWSCs) hold promise for sustainable H2 production in future energy systems, with Iodine-Sulfur (IS) and Nickel-Iodine-Sulfur (NIS) processes standing out as efficient options. The core of both these processes lies in the Bunsen reaction, underscoring the need to identify optimal operational conditions and plant solutions for this crucial reaction section. Thus, in this study, a continuous counter-current flow Bunsen reactor fed with 5 NL h−1 of SO2 was constructed and tested. An inventive aspect was the introduction of solid I2 pellets from the top to enhance saturation at the liquid-liquid interface between sulfuric and hydriodic product phases, promoting segregation. This ingenious design achieved nearly complete SO2 conversion and optimal H2SO4 and HI concentrations in the respective product phases, while avoiding undesirable byproduct formation. The study further advanced the modelling of the experimental reactor by employing innovative kinetic and liquid-liquid equilibrium description approaches, and demonstrating exceptional validation accuracy of R2 = 0.9988. Additionally, with the aim of obtaining design charts as a potential tool for Bunsen reactor design, a microscopic model describing the gas phase trend along bubble or packed Bunsen-type reactors was developed. The model’s dimensionless analysis revealed a characteristic times ratio (Bu) comprehensively describing all the phenomena occurring to the gas phase within the Bunsen reaction section, and identified an optimal Bu value of 0.4 for pure SO2 gas inlet. Overall, the study's innovative strategies and models contribute significantly to the advancement of Bunsen reactor engineering.

HI decomposition over the HI-100 test apparatus at a hydrogen production rate over 100 L/h

Studies on the iodine-sulfur (IS) thermochemical cycle for hydrogen production has been carried out since about 2005 by the Institute of Nuclear and New Energy Technology, Tsinghua University, China. The HI decomposition occupies the important position of hydrogen generation in the IS cycle. In this paper, the HI-100 test apparatus with a H2 production rate of 100 L/h was constructed and the HI decomposition was tested. First, the process and components for HI decomposition were designed. Then, the key components, including the feed tank, evaporator, gas heater, adiabatic reactor, condenser, and gas-liquid separator were made of industrial materials. After building this apparatus, the sealing test, heating water test, and HI decomposition have been conducted. The stable hydrogen production operation of more than 100 L/h had been achieved for 5 h, the maximum hydrogen production reached approximately 130 L/h, and the hydroiodic acid decomposition rate maintained about 22 %. The test results provide the design and experimental guidance for further amplification of HI decomposition for hydrogen production by the IS cycle.

Process modelling and assessment of thermochemical sulfur-iodine cycle for hydrogen production considering Bunsen reaction kinetics

Thermochemical sulfur-iodine (SI) cycle is one of the large-scale, clean, and efficient hydrogen production routes. The Bunsen reaction process is always simulated by a stoichiometric reaction, without considering the realistic Bunsen reaction kinetic process. Herein, a user-defined Fortran module concerning Bunsen reaction kinetics was developed and embedded into a continuous stirred tank reactor (RCSTR), and then a SI flowsheet with 100 L/h hydrogen production was modeled. The key parameter optimization, mass and energy balance were analyzed, the internal heat exchange network was created using the pinch point temperature difference analysis and the principle of energy cascade utilization, along with thermal efficiency evaluation. Bunsen reaction process reaches equilibrium after a period, which is consistent with experiments. The increase of H2SO4 decomposition ratio is beneficial to reduce the energy consumption of system. Increase in temperature has less effect on increasing the equilibrium decomposition ratio of HI. The theoretical thermal efficiency of system reaches 14.0–57.4 % considering the recovery of exothermic heat. This work provides a theoretical basis for the optimization of SI cycle.

Corrosion behavior of SiC coated HX with MoSi2 interlayer to be utilized in iodine–sulfur cycle for hydrogen production

In this era, renewable energy technologies are suitable to meet the challenges of fossil fuel depletion and global warming. Thus, hydrogen is gaining attention as an alternative clean energy carrier that can be produced from various methods, one of them is the iodine-sulfur (I–S) cycle which is a thermochemical process. The I–S cycle requires a material that can withstand an extremely corrosive environment at high temperatures. Immersion tests were conducted on bare superalloy Hastelloy X (HX), MoSi2, and SiC–MoSi2 coated HX, deposited in physical vapor deposition (PVD) to evaluate their corrosion resistance. Bare HX exhibited a high corrosion rate of 208.1 mm yr−1 when exposed to 98 wt% sulfuric acid at 300 °C. In contrast, HX with MoSi2 coating showed a much lower corrosion rate of 23.5 mm yr−1, and HX with SiC–MoSi2 coating demonstrated the lowest corrosion rate at 6.5 mm yr−1 under the same conditions. The coated samples were analyzed via FESEM before and after corrosion testing. The FESEM images reveal the formation of coalescent particles on the surface of the coating. The elemental analysis illustrates an increased concentration of silicon and oxygen in the corroded samples. Elemental mapping of these samples show a uniform distribution of elements over the sample. These findings contribute not only to materials science understanding but also to practical applications in hydrogen production via the I–S cycle, where corrosion-resistant materials are critical.

Economic evaluation of hydrogen production in second and third units of Bushehr nuclear power plant regarding future need of nuclear fission technology

Today, the most important challenge for hydrogen production is the use of suitable energy source for sustainable production. The dual use of nuclear power plants allows them to expand into other markets by eliminating greenhouse gas emissions from processes such as hydrogen production. The significance of this matter especially in countries with ongoing new nuclear power plants is high and shows the future need for nuclear fission technology. In this paper, an economic assessment of hydrogen production in the second and third units of the Bushehr nuclear power plant (BNPP) with the Hydrogen Economy Evaluation Program (HEEP) is carried out and a comparison of CO2 emission in nuclear and non-nuclear methods of hydrogen production is presented. Most nuclear reactors, including Advanced Pressurized WaterReactor (APWR), High Temperature Gas Reactor (HTGR), and Water-Water EnergeticReactor (WWER), can be used as a source of thermal and electrical energy for the process of hydrogen production. In this research, hydrogen production processes based on the Conventional Electrolysis (CE), High Temperature Steam Electrolysis (HTSE), and Sulfur-Iodine (SI) Process using different storage and transportation options are compared to choose the cost-effective method for coupling with the WWER1000 reactor. Hydrogen production, thermal energy, and electricity costs have been calculated and explained in detail. The results showed that the cost-effective option for hydrogen production is using the High Temperature Steam Electrolysis (HTSE) method, Compressed Gas (CG) storage, and pipeline transportation, by 2.88 $/kg. Also, applying this method to produce hydrogen, the nuclear power plant thermal efficiency, and the hydrogen plant efficiency are kept in the best possible conditions by 51.98% and 58.21%, respectively.

Design and evaluation of a novel process for green hydrogen production in the iodine–sulfur cycle via pressure-swing distillation of HIx (HI-I2-H2O)

In striving for carbon neutrality, hydrogen energy serves as a sustainable solution, and the iodine–sulfur (IS) cycle stands out as the most promising method for hydrogen production. The separation and purification of HI from the HIx (HI-I2-H2O) mixture holds significant research value, as they constitute the crucial aspect of the iodine–sulfur cycle in hydrogen production. Due to the azeotropic behavior of HI and H2O, the HIx system poses a considerable challenge. In this research, a technique for purifying HI via pressure-swing distillation was developed, exploiting the changes in azeotropic points under varying pressure conditions. The most effective method for HI purification was determined to be a three-column pressure-swing distillation configuration, as revealed by Aspen Plus phase diagrams and process topology mapping. It yielded H2O and I2 at the top of the first column, I2 at the bottom of the second column, and HI at the top of the third column with an HI recovery rate of 97 %. By analyzing the Bunsen reaction kinetics of the core reaction in the IS system, a comprehensive method for evaluating the separation and reaction coupling quality network of HIx cycle system using Bunsen-factor (B-factor) was proposed. The B-factor elucidates the correlation between the Bunsen reaction rate and the concentrations of [H+], [I-], [I3-], as well as the pH level. A comprehensive analysis of the B-factor was conducted for the pressure-swing distillation topologies of the HIx system, and the results were contrasted with those of alternative separation processes. The findings indicated that the three-column pressure-swing distallation is the most suitable option for both separation and reaction quality in a recycled network. The total energy consumption of the newly designed HIx three-column process is 352 MJ/kmol, rendering it more economical and beneficial than other processes. This study presents a pressure-swing distillation method for HI separation and purification, which is broadly applicable in IS cycles and aids in achieving large-scale production of green H2. This method enables the achievement of the dual-carbon objective, which seeks to mitigate carbon emissions while safeguarding the environment.

Decoupling the anodic and cathodic behavior in asymmetric electrochemical hydroiodic acid decomposition cell for hydrogen production in the iodine-sulfur thermochemical cycle.

The HI section of the iodine-sulfur (I-S) thermochemical cycle for hydrogen production is one of the most energy-intensive sections and with significant material handling challenges, primarily due to the azeotrope formation and the corrosive nature of the hydroiodic acid-iodine-water mixture (HIx). As an alternative, the single-step direct electrochemical decomposition of the hydroiodic acid (HI) to generate hydrogen can circumvent the challenges associated with the conventional multistep HI section in the I-S cycle. In this work, we present new insights into the electrochemical HI decomposition process by deconvoluting the contributions from the anodic and the cathodic sections in the electrochemical cell system, specifically, the redox reactions involved and the overpotential contribution of the individual sections (anolyte and catholyte) in the overall performance. The studies on the redox reactions indicate that the HIx solution output from the Bunsen reaction section should be used as the anolyte. In contrast, aqueous HI without any iodine (I2) should be used as the catholyte. In the anodic section, the oxidation proceeds with I2 as the final oxidized species at low bias potentials. Higher positive potentials result in iodate formation along with oxygen evolution. For the catholyte section, I2 and tri-iodide ion reduction precede the hydrogen evolution reaction when I2 is present along with HI. Furthermore, the potential required for hydrogen production becomes more negative with an increasing I2/HI ratio in the catholyte. Polarization studies were conducted with simultaneous deconvolution of the anodic and cathodic behavior in a two-compartment cell. Model fitting of the polarization data revealed that the anolyte section's activation overpotential is negligibly low. In contrast, the activation overpotential requirement of the catholyte section is higher and dictates the onset of hydrogen production in the cell. Furthermore, the catholyte section dominates the total overpotential losses in the cell system. Operation in the ohmic resistance-dominated zone resulted in close to 90% current efficiency for the electrochemical HI decomposition. The results highlight that the potential for process improvement lies in reducing the ohmic resistance of the anolyte section and in lowering the activation overpotential of hydrogen evolution in the catholyte section.

Insights into the stability of the iron oxide immobilized into mesoporous silica catalysts in iodine–sulfur cycle for hydrogen production

Insights into the stability of the iron oxide immobilized into mesoporous silica catalysts in iodine–sulfur cycle for hydrogen production

A comprehensive evaluation integrating thermodynamics and mechanism kinetics for the Bunsen reaction in a sustainable iodine–sulfur cycle

Carbon neutrality makes hydrogen a promising alternative source of energy. Iodine-sulfur cycle shows the greatest potential among hydrogen production methods. Bunsen reaction holds significant research value as the core reaction of the iodine-sulfur cycle. This paper presents an innovative method for evaluating Bunsen reactions, integrating equilibrium thermodynamics and kinetics to explore the influence of temperature, pressure, and reactant concentration on the Bunsen reaction. The thermodynamic results show that the influence of pressure on reaction balance is weak; with the gradual excess of I2, the amount of H2O required for Bunsen reaction decreases; the optimal operation ratio of H2O:I2:SO2 is 16:4:1 at 360K; the Bunsen reaction system should be carried out in an acidic system, while H2O promotes the spontaneous exothermic reaction of Bunsen. Additionally, we propose 8 reactions as Bunsen reaction mechanisms, and derive the rate equation. Bunsen reaction rates are promoted by [I2], [I3−], and [SO2] concentrations, inhibited by [I−] and [H+] concentrations, and the reaction rate of the whole solution system is sensitive to pH, [I−] and [H+] concentration changes. Added H2O improves pH, whereas acidic systems benefit from higher pH. Lastly, the interconnection of thermodynamic and kinetic results is discussed and compared with other literature. The method proposed in this study has universal application value for Bunsen reaction. It contributes to system process optimization and Bunsen reactor amplification, and facilitating carbon neutralization and hydrogen energy.

Evaluation and comparison of hydrogen production potential of the LIFE fusion reactor by using copper–chlorine (Cu–Cl), cobalt–chlorine (Co–Cl) and sulfur–iodine (S–I) cycles

In this paper, the hydrogen production and neutronic analysis of the Laser Inertial Confinement Fusion-Fission Engine (LIFE) fusion reactor have been analyzed. The potential of hydrogen production from unit integrated of the reactor with three different hydrogen production methods which has copper-chlorine (Cu–Cl) cycle, cobalt-chlorine (Co–Cl) cycle and sulfur-iodine (S–I) cycle have been investigated. Neutronic performance analysis for various parameters was calculated statically by using Monte Carlo N-Particle Nuclear Code and determined optimum reactor operation conditions. The hydrogen production potential for all conditions was investigated as statically. And also, the production potential with determining optimum conditions was performed over operation plant. Tristructural isotropic (TRISO) coated thorium carbide (ThC) was used as fuel of LIFE fusion reactor. Natural lithium and FLiNaBe (LiF + NaF + BeF2) were used first and second coolant, respectively. In the statistical analysis, effects of ThC fuel ratio, 1st and 2nd coolant zone thicknesses were examined. As a consequence of the neutronic analysis, tritium breeding values and energy multiplication values (M) was attained and according to M values, hydrogen production amount, required thermal power and thermal power ratios were acquired. Among the used hydrogen production methods, Cu–Cl cycle produced the highest hydrogen amount, while the Co–Cl cycle has the lowest H2 amount. At the end of the reactor operation time for determining optimum conditions, the produced hydrogen amounts are 9.00, 4.80 and 7.36 kg/s for Cu–Cl, Co–Cl and S–I cycles, respectively.

Experimental and numerical investigation of sulfuric acid decomposition for hydrogen production via iodine–sulfur cycle

In the context of global warming and the greenhouse effect, the iodine–sulfur cycle is an important method of producing hydrogen on a large scale with low carbon emissions using nuclear energy for future applications. The sulfuric acid decomposition reaction is a key step in this process. A sulfuric acid decomposer with good performance usually has the characteristics of high decomposition rate, small pressure drop loss and reasonable temperature distribution, which can ensure the efficient and stable process of sulfuric acid decomposition. Therefore, an accurate evaluation of the performance of the sulfuric acid decomposer unit and the reproducibility of the whole process is of utmost importance for designing and engineering an actual system for hydrogen generation. In this work, two sets of experimental systems were designed to measure the important kinetic parameters of sulfuric acid decomposition reaction and to determine the thermal hydraulics and chemical reaction performance indicators of the system. Then, a multi-field coupling model in which the phase change and chemical reactions were coupled by user-defined functions was developed based on the experimental kinetic parameters to account for the whole process. The thermal–hydraulic characteristics and the chemical reaction indexes predicted by the model are in good agreement with the experimental results. The maximum errors of the sulfuric acid decomposition fraction and pressure drop do not exceed 5% and 10%, respectively. Overall, this work provided a complete model for predicting the performance of the sulfuric acid decomposer.

A Universal Strategy Toward Low‐Cost Aqueous Sulfur–Iodine Batteries

AbstractRechargeable aqueous batteries with non‐toxic and non‐flammable features are promising candidates for large‐scale energy storage. However, their practical applications are impeded by the insufficient electrochemical stability windows of aqueous electrolytes and intrinsic drawbacks of current electrodes. Herein, an aqueous sulfur–iodine chemistry that can be deployed in aqueous battery systems by employing water‐in‐bisalt (WiBS) electrolyte, sulfur composite anode, and iodine composite cathode is demonstrated. The freestanding iodine/carbon cloth cathode and halide‐containing WiBS electrolyte can support the continuous I+/I0 reaction by forming interhalogen. Meanwhile, the highly‐concentrated electrolyte and inorganic‐based solid electrolyte interphase can effectively suppress the dissolution/diffusion of polysulfides, thus realizing S/Sx2− conversion reactions on the anode. Therefore, the as‐assembled aqueous sulfur–iodine batteries based on S/Sx2− and I+/I0 redox couples can deliver a high energy density of 158.7 Wh kg−1 with a considerable cycling performance and safety. Furthermore, this chemistry can be further extended to multivalent ion‐based battery systems. As demonstration models, Ca‐based and Al‐based aqueous sulfur–iodine batteries are also fabricated, which provide a new avenue towards the development of aqueous batteries for low‐cost and highly safe energy storage.