Active Dissolution Research Articles

Clarifying the Relationship Between Chemical States of P in Fe–P Alloys and Pitting Corrosion Resistance

Fe–0.002 P, Fe–0.05 P, Fe–0.2 P, and Fe–2 P alloys (numbers indicate the mass%) were fabricated, and their pitting potentials, depassivation pH values, and active dissolution rates were measured. The order of pitting potentials was (high) Fe–0.002 P ≥ Fe–0.05 P ≥ Fe–0.2 P ≫ Fe–2 P (low), and that of depassivation pH values was (low) Fe–0.002 P ≤ Fe–0.05 P ≤ Fe–0.2 P ≪ Fe–2 P (high). Both parameters changed significantly between the Fe–0.2 P and Fe–2 P alloys. No evidence of grain boundary segregation of P was observed in the Fe–0.05 P alloy. In the Fe–0.2 P alloy, grain boundary segregation of P was observed, but no pitting occurred at the grain boundaries. In the Fe–2 P alloy, Fe3P precipitated at the grain boundaries and in grains, but pitting corrosion occurred in the alloy matrix and not in Fe3P. This indicated that P in the solid solution was the main cause of the decrease in pitting corrosion resistance. The P concentration in the surface oxide film on Fe–2 P was higher than that on Fe–0.2 P, and the P in the films was determined to be FePO4. The decrease in the pitting resistance with an increasing P concentration was due to FePO4.

Enhancement in clinker hydration degrees and later stage-ettringite stability of calcium sulfoaluminate cements by the incorporation of dolomite

The hydration degrees of clinkers and ettringite stability in calcium sulfoaluminate (C A) cements in the presence of externally supplied dolomite were investigated in this study. The mineralogical and microstructural characteristics of C A cements containing different dosages of dolomite were characterized using X-ray diffractometry, Rietveld refinement-based quantification analysis, thermogravimetry analysis, mercury intrusion porosimetry, scanning electron microscopy observation, and energy dispersive spectroscopy point analysis. Furthermore, the binder systems were simulated using thermodynamic modeling to observe the phase changes of hydration products and the underlying hydration kinetics. The incorporation of dolomite accelerated clinker consumption and enhanced the stability of ettringite throughout the testing period, due possibly to the nucleation seeding effect and provision of carbonate ions by dolomite. The modeling outcomes showed the stability of ettringite at later stage by the incorporation of dolomite in the simulated timeframe, yet the active dissolution of dolomite assumed in the modeling procedure overestimated the Mg-bearing hydrates in the samples.

Simultaneous Inhibition of Vanadium Dissolution and Zinc Dendrites by Mineral‐Derived Solid‐State Electrolyte for High‐Performance Zinc Metal Batteries

Designing solid electrolyte is deemed as an effective approach to suppress the side reaction of zinc anode and active material dissolution of cathodes in liquid electrolytes for zinc metal batteries (ZMBs). Herein, kaolin is comprehensively investigated as raw material to prepare solid electrolyte (KL‐Zn) for ZMBs. As demonstrated, KL‐Zn electrolyte is an excellent electronic insulator and zinc ionic conductor, which presents wide voltage window of 2.73 V, high ionic conductivity of 5.08 mS cm‐1, and high Zn2+ transference number of 0.79. For the Zn//Zn cells, superior cyclic stability lasting for 2200 h can be achieved at 0.2 mA cm‐2. For the Zn//NH4V4O10 batteries, stable capacity of 245.8 mAh g‐1 can be maintained at 0.2 A g‐1 after 200 cycles along with high retention ratio of 81%, manifesting KL‐Zn electrolyte contributes to stabilize the crystal structure of NH4V4O10 cathode. These satisfying performances can be attributed to the enlarged interlayer spacing, zinc (de)solvation‐free mechanism and fast diffusion kinetics of KL‐Zn electrolyte, availably guaranteeing uniform zinc deposition for zinc anode and reversible zinc (de)intercalation for NH4V4O10 cathode. Additionally, this work also verifies the application possibility of KL‐Zn electrolyte for Zn//MnO2 batteries and Zn//I2 batteries, suggesting the universality of mineral‐based solid electrolyte.

Simultaneous Inhibition of Vanadium Dissolution and Zinc Dendrites by Mineral-Derived Solid-State Electrolyte for High-Performance Zinc Metal Batteries.

Designing solid electrolyte is deemed as an effective approach to suppress the side reaction of zinc anode and active material dissolution of cathodes in liquid electrolytes for zinc metal batteries (ZMBs). Herein, kaolin is comprehensively investigated as raw material to prepare solid electrolyte (KL-Zn) for ZMBs. As demonstrated, KL-Zn electrolyte is an excellent electronic insulator and zinc ionic conductor, which presents wide voltage window of 2.73 V, high ionic conductivity of 5.08 mS cm-1, and high Zn2+ transference number of 0.79. For the Zn//Zn cells, superior cyclic stability lasting for 2200 h can be achieved at 0.2 mA cm-2. For the Zn//NH4V4O10 batteries, stable capacity of 245.8 mAh g-1 can be maintained at 0.2 A g-1 after 200 cycles along with high retention ratio of 81%, manifesting KL-Zn electrolyte contributes to stabilize the crystal structure of NH4V4O10 cathode. These satisfying performances can be attributed to the enlarged interlayer spacing, zinc (de)solvation-free mechanism and fast diffusion kinetics of KL-Zn electrolyte, availably guaranteeing uniform zinc deposition for zinc anode and reversible zinc (de)intercalation for NH4V4O10 cathode. Additionally, this work also verifies the application possibility of KL-Zn electrolyte for Zn//MnO2 batteries and Zn//I2 batteries, suggesting the universality of mineral-based solid electrolyte.

Reactivation of dissolved polysulfides with nitrogen doped graphene decorated carbon cloth as an effective interlayer for magnesium-sulfur battery

The theoretically high energy densities and wide availability of active materials have led to great interest in the development of magnesium‑sulfur (MgS) batteries. However, poor electronic conductivity of sulfur, active material dissolution, polysulfide shuttling, and poor cycling stability are major challenges that need to be tackled. Herein we observed the pristine MgS cell faces significant overcharging issues and cell failure is common within 30 cycles with significant capacity decay. With the help of XRD and elemental mapping realized that the dissolved liquid polysulfides are metastable in nature. Due to the high sulfophilic nature of the separator, polysulfide absorption leads to slow crystal growth inside the separator. This active material trapping might be the reason for quick capacity decay. We attempted to revive the dissolved polysulfides by introducing conductive nitrogen-doped graphene (N-gpn)@Carbon cloth(CC) interlayer between the electrodes and separator. This interlayer has a high polysulfide absorption nature, which allows the battery to demonstrate an initial capacity of 1075 mAh g−1 and increased cycling stability to 100 cycles. However, this stability was further enhanced to 300 cycles by protecting the anode. Theoretical considerations suggest that among all polysulfides, MgS8, has the strongest interaction with N-gpn and can be trapped most favorably in a defective N-gpn. This leads to enhanced utilization of the active material and improved cycling stability.

Planar Disk μ-Aptasensors by Monolayer Assembly in a Dissolving Microdroplet.

Electrochemical aptamer-based sensors provide a highly modular platform for real-time monitoring of small molecules. Their ability to selectively recognize target molecules in complex environments like biological fluids makes them an attractive technology for the analysis of micro- and nanoscale systems. The signal-to-noise of the measurement depends on the electroactive surface (i.e., how many aptamers one can place), which has previously precluded miniaturization of aptamer-based sensors to planar disk ultramicroelectrodes (r ∼ 5-10 μm). Here, we employ a concentration enrichment strategy based on the active dissolution of an aqueous, aptamer-containing microdroplet on an ultramicroelectrode submerged in an organic continuous phase (1,2-dichloroethane). We show consistent voltammetric signal increase as a function of droplet lifetime, indicating the successful immobalization of the thiol-terminated aminoglycoside aptamers to the electrode surface. We observe a diagnostic methylene blue peak and 10-fold increase in current magnitude as compared to bare microelectrodes. We report robust sensor behavior with a linear dynamic range extending from milli- to micromolar concentrations of kanamycin in buffer. This research offers a successful method for optimized electrochemical aptamer-based sensor fabrication and miniaturization on ultramicroelectrodes without the need for electrode surface area enhancement.

Hydrogen Absorption and Self-Corrosion of Mg Anode: Influence of Aqueous Electrolyte Species

This review examines the impact of various aqueous electrolytes on hydrogen absorption and self-corrosion in magnesium (Mg) anodes. The discussion integrates both historical and recent studies to explore the mechanisms behind self-corrosion and anomalous hydrogen evolution (HE) under conditions of the Negative Difference Effect (NDE) and Positive Difference Effect (PDE). The focus is on the formation and oxidation of magnesium hydride in regions of active dissolution under NDE conditions. In the case of PDE, anodic dissolution occurs through the passive MgO-Mg(OH)₂ film, which shields the metal from aqueous electrolytes, thereby reducing hydrogen absorption and abnormal HE. The NDE conditions showed delayed reduction activity at the surface, attributed to a hydride phase within the corrosion product layer. Hydride ions were quantified through their anodic oxidation in an alkaline electrolyte, measured by the electric charge passed. The review also considers the role of de-passivating halide ions, electrolyte acidity buffering, and the addition of ligands that form stable complexes with Mg2⁺ ions, on the rates of hydride formation, self-corrosion, and anodic dissolution of Mg. The study evaluates species that either inhibit or promote hydrogen absorption and self-corrosion.

A 2-D Reaction-Transport Model for Investigating Pit Morphology Under the Influence of a Salt Film

A 2-D reaction transport model with the phase field method was employed here to simulate the propagation stage of corrosion pitting in stainless steels in a chloride environment. The influence of the salt film on pitting dissolution kinetics was incorporated into the model to study its effect on the pit morphology under various settings. In potentiostatic conditions, the pit morphology tends toward a dish-like shape due to the presence of the salt film inside a corrosion pit. This leads to diffusion-controlled dissolution at the pit bottom and active dissolution near the pit mouth. On the contrary, in galvanostatic conditions and at a high applied current, although the salt film was initially present, its effect diminished as the chemistry inside the pit became diluted and the pit growth transitioned into active dissolution near the repassivation current. This effect is attributed to the limited resources to support the enlargement of a corrosion pit under constant applied current. As a result, the pit morphology in galvanostatic conditions is likely to be hemispherical and can transition into complex morphology, as discussed in a previous paper.

Stress Corrosion Cracking of 304 Austenitic Stainless Steel in H2SO4/NaCl Media at Room Temperature

The effects of Cl− ion concentration, H2SO4 concentration, the applied potential, and the strain rate on the stress corrosion cracking (SCC) of 304 stainless steel were investigated. The postfracture scanning electron microscope micrographs of the fractured surfaces revealed that solutions of high H2SO4 concentration combined with low Cl− ion concentration resulted in corrosion (active dissolution), while solutions of very low H2SO4 concentration combined with a relatively moderate Cl− ion concentration resulted in ductile failure. Solutions with moderate concentrations of H2SO4 and Cl− ions resulted in transgranular SCC. The susceptibility to SCC and the fracture surface morphology were found to depend on the [H2SO4]/[Cl−] ratio, the strain rate, and the applied potential. The average crack-growth rate (ACGR) was found to depend on the strain rate and the applied potential. For specimens undergoing SCC at the open-circuit potential, the ACGR increased with increasing the strain rate. For specimens undergoing SCC under applied potential in the active range, the ACGR increased with increasing the applied potential. The specimen eventually failed in a ductile manner when tested under an applied anodic potential in the passive range. The increase in the ACGR with increasing strain rate and the applied anodic potential is attributed to the enhanced dissolution at the crack tip. Moreover, secondary cracks formed when relatively high strain rates were used. The secondary cracks are believed to propagate mainly along the slip planes. The fracture surface morphology shows the {110} planes are the preferred fracture planes, with the fracture surface consisting of parallel facets separated by steps. Finally, the results indicate that hydrogen may play an indirect role in SCC.

Mullite Mineral-Derived Robust Solid Electrolyte Enables Polyiodide Shuttle-Free Zinc-Iodine Batteries.

Zinc dendrite, active iodine dissolution, and polyiodide shuttle caused by the strong interaction between liquid electrolyte and solid electrode are the chief culprits for the capacity attenuation of aqueous zinc-iodine batteries (ZIBs). Herein, mullite is adopted as raw material to prepare Zn-based solid-state electrolyte (Zn-ML) for ZIBs through zinc ion exchange strategy. Owing to the merits of low electronic conductivity, low zinc diffusion energy barrier, and strong polyiodide adsorption capability, Zn-ML electrolyte can effectively isolate the redox reactions of zinc anode and AC@I2 cathode, guide the reversible zinc deposition behavior, and inhibit the active iodine dissolution as well as polyiodide shuttle during cycling process. As expected, wide operating voltage window of 2.7V (vs Zn2+/Zn), high Zn2+ transference number of 0.51, and low activation energy barrier of 29.7kJ mol-1 can be achieved for the solid-state Zn//Zn cells. Meanwhile, high reversible capacity of 127.4 and 107.6 mAh g-1 can be maintained at 0.5 and 1 A g-1 after 3000 and 2100 cycles for the solid-state Zn//AC@I2 batteries, corresponding to high-capacity retention ratio of 85.2% and 80.7%, respectively. This study will inspire the development of mineral-derived solid electrolyte, and facilitate its application in Zn-based secondary batteries.

Syndepositional and diagenetic processes in the pigmentation of Middle Ordovician carbonate red beds in South China

Marine red beds (MRBs) are often attributed to specific redox environments during syndepositional and early diagenetic phases. During the Middle Ordovician, a succession of reddish, deeper-water nodular argillaceous limestones (i.e., Zitai and Kuniutan formations) were deposited along the margin of Yangtze Platform in South China. However, the origin of their color remains enigmatic. In this study, we investigated the Middle Ordovician MRBs from a borehole core newly drilled in the Lower Yangtze area of South China whose stratigraphy frameworks are constrained by carbon isotope and biostratigraphy. This study investigates the pigmentation of these MRBs by integrating petrographic observations, elemental geochemistry, diffusive reflectance spectrometry (DRS), and scanning electron microscope (SEM) coupled with energy dispersive X-ray spectrometry (EDS). DRS results show that the red pigment is caused by hematite particles in submicron- to micron-level size. SEM demonstrates that the hematite grains are either detrital grains with traces of physical transport from terrestrial source, or flaky amorphous hematite aggregates situated within the calcite crystal interstices, implicating both syndepositional and early diagenetic origins, respectively. In terms of the geochemical result of the bulk rocks, the close positive correlation between Al2O3 and Fe2O3 indicates that the iron pigment materials may mainly originate from terrestrial Fe-bearing phyllosilicates. These observations are also consistent with the distribution patterns of rare earth elements (REEs) in carbonate leachates. The MRB limestones are characterized by MREE-bulged patterns and close to ~1 Ce anomalies, suggesting active reductive dissolution and subsequent reprecipitation of iron oxides during diagenesis in pore systems. This study proposes that the coloration of Middle Ordovician MRBs in Lower Yangtze Platform was linked to the enhanced input of terrestrial clay minerals rich in iron. The reductive dissolution released iron ions from terrestrial detrital and allowed subsequent reprecipitation of iron-oxides in pore water system during the fluid-buffered diagenesis. In this light, hematites formed during both the syndepositional and diagenetic processes thus could have involved the coloration of the Middle Ordovician carbonate red beds in this case.

Microstructure, mechanical properties and corrosion behavior of W-B-Ni-Fe shielding cermets synthesized by reactive boride sintering

In this work, a novel type of nuclear shielding material capable of shielding γ rays and neutrons, W-B-Ni-Fe cermets, was synthesized using W, NiB, and Fe powders by reactive boride sintering. The cermets possessed a constant (Ni + Fe)/B atomic ratio of 1.50 and various W/B atomic ratio (ARWB) of 8.26, 3.25, 1.88 and 1.24, respectively. Microstructure and mechanical properties were characterized and analyzed, and corrosion behavior was discussed using electrochemical method in 1.0 M H2SO4 aqueous solution. After sintering, the cermets were composed of orthorhombic W2(Ni,Fe)B2 hard phase, W phase and Ni based binder phase. The homogeneous microstructure with both fine W2(Ni,Fe)B2 and W particles was obtained when ARWB was 3.25. At room temperature (RT), the hardness increased monotonically with ARWB decreasing, while the compressive and bending strengths peaked when ARWB was 3.25 due to the cooperativeeffect of hard-phase and grain-refinement strengthening. At high temperature (500 ℃), the presence of ductile W phase enabled an increase of bending strength compared to that at RT. The corrosion of cermets in 1.0 M H2SO4 solution began with active dissolution of Ni based binder phase, and then the passivation process occurred with the formation of blue WO3-x phase. With ARWB decreasing, Icorr was first sharply decreased and then sharply increased. The impedance value of cermet was lowest when ARWB was 3.25 which is due to the relatively lower forming ability of passive film.

Inhibiting Dissolution of Active Sites in 80 °C Alkaline Water Electrolysis by Oxyanion Engineering

AbstractCommercial alkaline water electrolysers typically operate at 80 °C to minimize energy consumption. However, NiFe‐based catalysts, considered as one of the most promising candidates for anode, encounter the bottleneck of high solubility at such temperatures. Herein, we discover that the dissolution of NiFe layered double hydroxides (NiFe‐LDH) during operation not only leads to degradation of anode itself, but also deactivates cathode for water splitting, resulting in decay of overall electrocatalytic performance. Aiming to suppress the dissolution, we employed oxyanions as inhibitors in electrolyte. The added phosphates to the electrolyte inhibit the loss of NiFe‐LDH active sites at 400 mA cm−2 to 1/3 of the original amount, thus reducing the rate of performance decay by 25‐fold. Furthermore, the usage of borates, sulfates, and carbonates yields similar results, demonstrating the reliability and universality of the active site dissolution inhibitor, and its role in elevated water electrolysis.

Inhibiting Dissolution of Active Sites in 80 °C Alkaline Water Electrolysis by Oxyanion Engineering.

Commercial alkaline water electrolysers typically operate at 80 °C to minimize energy consumption. However, NiFe-based catalysts, considered as one of the most promising candidates for anode, encounter the bottleneck of high solubility at such temperatures. Herein, we discover that the dissolution of NiFe layered double hydroxides (NiFe-LDH) during operation not only leads to degradation of anode itself, but also deactivates cathode for water splitting, resulting in decay of overall electrocatalytic performance. Aiming to suppress the dissolution, we employed oxyanions as inhibitors in electrolyte. The added phosphates to the electrolyte inhibit the loss of NiFe-LDH active sites at 400 mA cm-2 to 1/3 of the original amount, thus reducing the rate of performance decay by 25-fold. Furthermore, the usage of borates, sulfates, and carbonates yields similar results, demonstrating the reliability and universality of the active site dissolution inhibitor, and its role in elevated water electrolysis.

An Investigation of Corrosion Behaviors of Thermally Sprayed Aluminum (TSA) at Elevated Temperatures Under Thermal Insulations and Autoclave Immersion Conditions

ABSTRACT Thermally Sprayed Aluminum (TSA) protects against internal and external corrosion in many industrial applications. Even though TSA coating has been the subject of many studies, there is still a need to gain better insights into the degradation mechanisms of the TSA especially under immersion conditions and moisture-saturated thermal insulations. This study addresses the corrosion behavior of TSA in a CUI simulation setup (per ASTM G189-07) and autoclave immersion. The corrosion tests were conducted for three and four days under isothermal wet (IW) and cyclic wet (CW) conditions. Linear polarization resistance (LPR) scans were conducted during both (i.e., CUI simulation and autoclave immersion tests) to better understand the corrosion behaviors of TSA coating. Following corrosion testing, thorough microstructural examinations were conducted employing confocal laser microscopy, 3D topography, scanning electron microscopy (SEM), and Energy dispersive spectroscopy (EDS) to understand the microstructural and tribological changes resulting from corrosion testing. TSA coating under the insulation showed significant degradation via flashing moisture and active dissolution of iron at the insulation-metal interface. Unlike immersion conditions, the wear of TSA due to flashing moisture under thermal insulation created the crevices that caused the active corrosion of the steel substrate.

Recovery of neodymium and iron from NdFeB waste by combined electrochemical–hydrometallurgical process

The recovery of rare-earth elements and Fe from NdFeB waste has significant potential. However, conventional hydrometallurgical and pyrometallurgical processes are energy intensive, chemical consuming, and accompanied by waste emissions, resulting in low-value iron products. This study introduced a combined electrochemical–hydrometallurgical process for NdFeB waste recovery. Electrochemical analysis revealed the active dissolution of NdFeB waste under 370 mA/cm2, enabling Fe2+ reduction to Fe even in the presence of Nd3+. Electrolysis at 60 °C using Nd2(SO4)3 and FeSO4 as electrolytes, along with H3BO3 as a pH buffer, resulted in the uniform dissolution of waste, releasing Nd3+ and Fe2+ into the electrolyte, whereas Fe2+ underwent electrodeposition onto Fe at the cathode. Investigation of FeSO4 concentration revealed its influence on current efficiency, cathode-product properties, and energy consumption. When the concentration of FeSO4 was 0.5 M, a cathode product with 87.94 wt% Fe and 0.03 wt% Nd was obtained. Finally, Nd was recovered by hydrometallurgical high-temperature crystallization at 90 °C under N2 atmosphere, yielding Nd2(SO4)3·nH2O mixed crystals with 0.1 wt% Fe. The process formed a closed loop, consuming only FeSO4 and a minimal amount of H2SO4, with an energy consumption of 0.73–1.53 kW·h/kg NdFeB.

Revealing the Mechanism of O<sub>2</sub> and Pressure Effects on the Corrosion of X80 Carbon Steel Under Supercritical CO<sub>2</sub> Conditions

Pipeline transportation is widely used due to its ability to improve the efficiency of CO<sub>2</sub> transportation in Carbon Capture, Utilization, and Storage (CCUS). Within the transport pipelines, CO<sub>2</sub> fluid exists in a supercritical state and often contains various impurity gases such as O<sub>2</sub> and H<sub>2</sub>O, which can easily cause steel corrosion, affecting the safety of pipeline operations. In this investigation, we examine the corrosion behavior of X80 carbon steel within a water-saturated supercritical CO<sub>2</sub> environment utilizing weight loss experiments, electrochemical tests, and surface analysis techniques. Furthermore, we explore the impact of pressure and oxygen on the corrosion process of X80 steel. The results indicated that X80 steel underwent severe corrosion under the experimental conditions, with FeCO<sub>3</sub> as the primary corrosion product. Both the introduction of oxygen and an increase in pressure accelerated the steel's corrosion, and the addition of oxygen led to the formation of a new corrosion product, Fe<sub>2</sub>O<sub>3</sub>. Electrochemical test results showed that changes in pressure did not significantly alter the electrochemical corrosion characteristics of the steel, but the introduction of oxygen decreased the electrochemical reaction resistance of X80 steel. Combined with surface analysis, the following conclusions were drawn: In a 50°C supercritical CO<sub>2</sub> environment, the anode reaction of X80 steel corrosion is the active dissolution of iron, while the cathode reaction involves the dissolution and ionization of CO<sub>2</sub>. Changes in pressure do not alter the corrosion mechanism, but the introduction of oxygen leads to oxygen corrosion reactions in the system, accelerating the anode reaction rate and thus increasing the degree of corrosion.

Investigating Capacity Fade Mechanisms in Dual-Ion Mg-MCl x Batteries

Mg batteries are a promising alternative to Li-based chemistries due to the high abundance, low cost, and high volumetric capacity of Mg relative to Li. Mg is also less prone to dendritic plating morphologies, promising safer operation. Mg plating and stripping is highly efficient in chloride-containing electrolytes; however, chloride is incompatible with many candidate cathode materials. In this work, we capitalize on the positive effect of chloride by using transition metal chloride cathodes with a focus on low cost, Earth-abundant metals. Both soluble and sparingly soluble chlorides show capacity fade upon cycling. Active material dissolution and subsequent crossover to the Mg anode are the primary drivers of capacity fade in highly soluble metal chloride cathodes. We hypothesize that incomplete conversion and chemical reduction by the Grignard-based electrolyte are major promoters of capacity fade in sparingly soluble metal chlorides. Modifications to the electrolyte can improve capacity retention, suggesting that future work in this system may yield low cost, high retention Mg-MClx batteries.

Rocking-Chair Aqueous Fluoride-Ion Batteries Enabled by Hydrogen Bonding Competition.

Aqueous fluoride ion batteries (FIBs) have garnered attention for their high theoretical energy density, yet they are challenged by sluggish fluorination kinetics, active material dissolution, and electrolyte instability. Here, we present a room temperature rocking-chair aqueous FIBs featuring KOAc-KF binary salt electrolytes, enabling concurrent fluorination and defluorination reactions at both cathode and anode electrodes. Experimental and theoretical results reveal that acetate ions in the electrolyte compete with fluoride ions in hydrogen bonding formation, weakening the excessively strong solvation between H2O and F- ions. This results in the suppression of detrimental HF formation and a reduced desolvation energy of F- ions, enhancing the electrochemical reaction kinetics. The bismuth-based cathode exhibits direct conversion in the optimized electrolyte, effectively suppressing the detrimental disproportionation reactions from Bi2+ intermediates. Additionally, zinc anode undergoes a typical fluorination process, forming solid KZnF3 as the electrode product, minimizing the risks of hydrogen evolution. The proposed aqueous FIBs with the optimized electrolyte demonstrate high discharge capacity, long-term cycling stability and excellent rate capabilities.

Rocking‐Chair Aqueous Fluoride‐Ion Batteries Enabled by Hydrogen Bonding Competition

AbstractAqueous fluoride ion batteries (FIBs) have garnered attention for their high theoretical energy density, yet they are challenged by sluggish fluorination kinetics, active material dissolution, and electrolyte instability. Here, we present a room temperature rocking‐chair aqueous FIBs featuring KOAc‐KF binary salt electrolytes, enabling concurrent fluorination and defluorination reactions at both cathode and anode electrodes. Experimental and theoretical results reveal that acetate ions in the electrolyte compete with fluoride ions in hydrogen bonding formation, weakening the excessively strong solvation between H2O and F− ions. This results in the suppression of detrimental HF formation and a reduced desolvation energy of F− ions, enhancing the electrochemical reaction kinetics. The bismuth‐based cathode exhibits direct conversion in the optimized electrolyte, effectively suppressing the detrimental disproportionation reactions from Bi2+ intermediates. Additionally, zinc anode undergoes a typical fluorination process, forming solid KZnF3 as the electrode product, minimizing the risks of hydrogen evolution. The proposed aqueous FIBs with the optimized electrolyte demonstrate high discharge capacity, long‐term cycling stability and excellent rate capabilities.