Ammonia (NH₃) is a versatile chemical, critical to agriculture and various industries. Today, ammonia is further regarded as one of the most promising carbon-free energy carriers in the net-zero hydrogen economy. Traditionally, the energy-intensive Haber Bosch process has been mainly used for producing ammonia by the thermocatalytic conversion of high-purity nitrogen and hydrogen, while also contributing to major greenhouse gas emissions due to dependence on fossil fuels. The electrochemical nitrogen reduction reaction (e-NRR) is a highly promising and attractive alternative roadmap to achieving clean and sustainable ammonia production under conditions that are sufficiently mild to be fully powered by renewable energy sources. However, the industrial adoption of e-NRR is currently hindered by its low ammonia yields, and poor selectivity resulting from the limited reactivity of nitrogen molecules and the competitive hydrogen evolution reaction (HER) in aqueous electrolyte, respectively. To overcome these barriers, the development of efficient electrocatalysts for e-NRR is essential to the actual realization of this emerging ammonia production technology. Among various types of promising materials, earth-abundant Fe element presents a competitive edge for developing high-performance electrocatalytic N₂ reduction systems owing to its intrinsic activity, low cost, and ease of modification with other elements to form compounds with distinguished catalytic activity. Therefore, this review focuses on recent developments in Fe-based nanomaterials for ammonia synthesis through e-NRR. A detailed overview of the chemistry of e-NRR, its fundamentals, mechanisms, and experimental procedures is given along with ammonia detection methods and catalyst evaluation metrics. The main part of this review explored various kinds of Fe-based catalysts encompassing the oxides, hydroxides, bimetallic catalysts, single atom catalysts (SACs), metal organic frameworks (MOFs), and chalcogenides. The analysis and discussion revolved around key traits of the catalysts including synthesis protocol, structural features, surface properties and their correlation to catalytic activity based on experimental data and theoretical insights. Additionally, prevailing challenges and opportunities for further advancement of Fe-based e-NRR catalysts are provided.

Aqueous aluminum batteries (AABs) have emerged as promising next generation batteries owing to their sustainability and high theoretical capacity. However, conventional aqueous electrolytes bring challenges, such as low voltage windows, and corrosion. Therefore, the new subclass of aqueous electrolytes, water-in-salt (WIS) electrolytes, are lately being considered. This study explores in detail aluminum/graphite (Al/G) cells utilizing WIS electrolytes. Parameters such as interelectrode distance, voltage range, and current density were investigated. The results revealed that cells with a 6 mm interelectrode distance, operating in the voltage range of 0.1–1.6 V at a current density of 0.5 Ag −1 , demonstrate the highest capacity (80 mAhg −1 ) in the stabilized cycle stage, compared with other configurations. • Al/graphite cell operation in a water-in-salt electrolyte was investigated and optimized. • The interelectrode distance significantly influenced the performance of the Al/graphite cell. • The cell within the voltage range of 0.1–1.6 V and a current density of 0.5 Ag −1 revealed the best cycling stability.

Stabilizing the zinc anode interface in aqueous electrolytes via multifunctional additive engineering for long-lifespan zinc-ion batteries

Electrolyte solutions are central to many industrial, geochemical, and biological processes, yet their thermodynamic modeling remains challenging. This work assesses the predictive performance of the eSAFT–VR Mie equation of state by focusing on two key modeling parameters: (i) the distance of closest approach, comparing the ion segment diameter ( σ ) with the effective hard–sphere diameter ( d ), and (ii) the choice of ion–ion combining rules, both dispersion–energy–based formulations, namely the Hudson–McCoubrey (CR1) and the modified Lennard–Jones (CR2) rules. Predictions of mean ionic activity coefficients (MIAC) and liquid densities were evaluated for 57 aqueous salts without additional parameter fitting. Results show that density is relatively insensitive to the choice of parameters, whereas MIAC exhibits salt– and concentration–dependent sensitivity, particularly for multivalent systems. The comparison of CR1 and CR2 highlights that no single combining rule performs universally best, with accuracy depending on the ion type and charge density. These findings provide guidance for selecting the parameters and improving predictive electrolyte models.

The Zn anode in aqueous zinc-ion batteries (AZIBs) suffers from hydrogen evolution reaction (HER), by-product accumulation, and dendrite growth, severely restricting practical viability. To address these challenges concurrently, we propose a dynamic Zn2+-conductive protective layer strategy, which involves constructing an in situ ZnOHF layer on the Zn anode and incorporating F- into the electrolyte. Zn2+-conductivity and reducibility of ZnOHF layer guide uniform Zn nucleation and deposition, thereby inhibiting dendrite formation. Crucially, the addition of F- to the electrolyte enables the dynamic regeneration of the ZnOHF layer during cycling and the conversion of detrimental by-products into favorable ZnOHF. Additionally, HER is effectively suppressed by isolating the Zn anode from the aqueous electrolyte via ZnOHF interfacial layer, and decreasing water activity through F--induced elevation of electrolyte pH from 4.1 to 5. As a result, the protected Zn anode enables the symmetrical cell to operate stably for 3100h at 0.5 mA cm-2, and a full cell to retain 85% capacity after 4000 cycles at 10 A g-1. Moreover, a 90 cm2 pouch cell delivers an initial capacity of 240 mAh and maintains 70% capacity after 200 cycles, highlighting its practical viability. This work presents an effective and scalable interface engineering approach to realize durable Zn anodes for practical AZIBs.

Sustainable aqueous zinc-ion batteries (AZIBs) have emerged as promising next-generation energy storage solutions, aligning with global initiatives to mitigate climate change and promote low-carbon transitions. Their appeal stems from the utilization of earth-abundant materials and aqueous electrolytes, which minimize reliance on scarce metals and alleviate the safety and environmental risks associated with organic-solvent-based systems. This review systematically evaluates the sustainability of AZIBs throughout their entire life cycle, encompassing material selection, cell manufacturing, operational use, and end-of-life recycling, while providing a forward-looking perspective on their advancement. However, critical hurdles to industrialization persist, including zinc dendrite growth, cathode dissolution, and restricted cycle life. To realize genuine sustainability, future research must prioritize green material innovations, such as bio-based binders, functional separators, and eco-friendly electrolytes, while implementing dry electrode fabrication and other low-impact manufacturing techniques. Adopting a comprehensive life-cycle approach guided by circular economy principles is vital for fostering synergistic optimization across design, production, use, and recycling, ultimately achieving a "cradle-to-cradle" system. Furthermore, supportive policies, cross-sector collaboration, and international standardization are essential to bridge the gap between laboratory research and large-scale application. Through systematic, multi-faceted innovation, sustainable AZIBs are well-positioned to drive the global energy transition.

Electrode materials play a crucial role in improving supercapacitor performance. In this work, MnS nanoparticles were incorporated into MoO3 to form a MoO3/MnS nanocomposite via hydrothermal synthesis, and the capacitive performance of the resulting supercapacitor electrodes was evaluated. Their electrochemical performances were studied in conjunction with KCl and Na2SO4 electrolytes. The generation of MoO3/MnS nanocomposite was confirmed by XRD analysis and HR-TEM imaging. It is found that the MnS nanoparticles altered the morphology of MoO3 from nanobelts to nanofibers and produced a defective, rough surface. The defective surface expanded the interlayer distance from 0.396 nm to 0.421 nm. In both ionic electrolytes, the MoO3/MnS composite demonstrated higher capacitive performance than the pristine MoO3. At 0.3 A g-1 current density, the estimated specific capacitance of MoO3/MnS was 387 F g-1 and 335 F g-1 in KCl and Na2SO4 electrolytes, respectively. In the symmetric two-electrode system, the MoO3/MnS shows a specific capacitance of 297 F g−1 at 1 A g−1, with an energy density of 33.37 Wh kg−1 and a power density of 450 W kg−1. The MoO3/MnS nanocomposite provides excellent 90% retention after 1000 continuous charging-discharging cyclic. The enhancement of electrochemical performance is attributed to the large surface area, defective morphology, and broader interlayer distance. This system bridges the gap between traditional batteries and capacitors, offering a unique approach to producing supercapacitor electrodes.

Redox-targeting flow batteries (RTFBs) present an attractive strategy for enhancing the energy density of conventional redox flow batteries (RFBs) by integrating heterogeneous energy storage materials as capacity boosters. However, nearly all RTFB systems have been developed with nonaqueous redox chemistries, while capacity boosters in aqueous storage systems are limited to anthraquinone chemistries. In this work, we expand the chemistry of aqueous RTFBs to viologen-based compounds by translating a nonaqueous RTFB into an aqueous platform. All redox chemistries of the prior nonaqueous RTFB-redox shuttles and solids-required a synthetic redesign to address challenges associated with promoting fast redox targeting reactions of organic solids and shuttles in aqueous media. The effects of molecular structure, ion pairing, and supporting electrolytes on RTFB performance are detailed in this report to provide a case study for developing future aqueous organic RTFBs. The redesigned RTFBs achieve 50% utilization of the aqueous capacity booster for charge storage.

The solvation properties of electrolytes are one of the primary drivers of the performance of concentrated aqueous-based batteries. In this study, we provide an understanding of the lithium solvation and its dynamics in an electrolyte derived from a deep eutectic solvent (comprising LiClO4, urea and water) by effectively correlating multinuclear (1H, 17O, 35Cl, and 7Li) diffusion nuclear magnetic resonance (NMR) spectroscopy with molecular dynamics (MD) simulations. The freely accessible static field gradient from a commercial NMR magnet was used to determine diffusion coefficients for all population-averaged constituents─Li+, ClO4-, urea, and water─at various concentrations. The diffusion ratios DLi+/Durea ≈ 1 and DLi+/DClO4- ≈ 1 for the concentrated 1:3:2 electrolyte suggest correlated ionic motion and transport dominated by a vehicular character rather than hopping mechanisms. Ab initio MD simulations reveal mixed Li solvation shell configurations, with substantial urea coordination (∼66% of Li+ with one or two urea molecules in the 1:3:2 system) and an increasing occurrence of contact ion pairs with concentration. This results in relatively slow ionic mobility with a cation transference number around 0.5. Ion cluster analysis reveals a systematic increase in the occurrence of contact ion pairs with concentration, yet cluster sizes remain far below percolation thresholds, consistent with vehicular transport. Residence time analysis further quantifies this picture: the characteristic diffusional length exceeds the inner-sphere solvation shell radius (Lc/Ls > 1) across all concentrations, providing evidence for vehicular-dominated transport. 17O diffusion NMR measurements (D17O/D1H > 1.2 in a concentrated system) provide insights into water dynamics despite significant experimental challenges from quadrupolar relaxation. These findings provide molecular-level insights into aqueous electrolytes based on deep eutectic solvents to further guide the rational design of aqueous battery systems.

Water-based electrolytes with wide electrochemical stable windows (ESW) are crucial for high-energy-density supercapacitors. Herein, an interfacial engineering strategy to broaden the ESW of water-based electrolytes is proposed. It is found that although introducing dimethyl sulfone (MSM) to aqueous electrolytes reduces water activity through hydrogen bonding, at high salt concentrations, MSM enters the ionic solvation layer and weakens its hydrogen bonding, which results in an ESW approximately 0.2 V higher than at low salt concentrations. Further mechanistic studies have revealed that the barrier layer formed by the enrichment of MSM at the electrode/electrolyte interface increases the overpotential of the water splitting reaction. Simultaneously, MSM contributes significantly to the high ESW by binding to and stabilizing the active intermediates generated during the water splitting process. Subsequently, a scalable solvent exchange-ion cross-linking phase separation strategy is developed. The synergistic effects of NaClO4, MSM, water, and the hydrogel framework enable an ESW of 5.2 V. The supercapacitor assembled with laser-induced graphene (LIG) electrodes exhibits an operating voltage up to 2.4 V, with a capacitance retention rate of 98% after 10 000 charge/discharge cycles. In addition, the device demonstrates excellent adaptability at various folding angles and across a wide temperature range of -40°C to 45°C.

Aqueous Zn-ion batteries (ZIBs), characterized by intrinsic safety, biocompatibility, and competitive energy density, represent an exceptionally compelling technology for grid-scale energy storage. However, the uncontrollable hydrogen evolution reaction, corrosion, and undesirable dendrite growth triggered by the aqueous electrolytes hamper the further development of ZIBs. In recent years, polysaccharide materials such as cellulose, chitosan, alginates, and cyclodextrins have been widely adopted as electrolyte components in the construction of advanced ZIBs, because of their intrinsically excellent hydrophilicity, environmental friendliness, renewable and abundant production, sufficient active groups, and strong mechanical stability. This review presents a comprehensive summary of the fundamental structures, preparation methods, and comprehensive properties of polysaccharide-based electrolytes. Aqueous ZIBs featuring polysaccharide-based hydrogels are highlighted for their versatile flexibility, high ionic conductivity, and strong adaptability to harsh temperature conditions. To address the active water-derived issues, polysaccharide additives are used to regulate the solvation structures of Zn2+ ions and stabilize the anode/electrolyte interface chemistry. Finally, the performance metrics of these strategies are summarized, and the challenges and future perspectives are discussed.

We investigate ion pairing dynamics in electrolytes driven far from equilibrium using molecular simulations and nonequilibrium rate theory. Focusing on 0.5M LiPF6 in water and acetonitrile under uniform electric fields, we compute transition path theory observables, including reactive fluxes and mean first-passage times of ion pairing. Moreover, we introduce a dynamical proxy of free-ion population, where its field-induced change is strongly correlated with the nonlinear enhancement of conductivity, yielding an increase of 40% at 50mV/Å in acetonitrile, compared to that of less than 10% in aqueous electrolytes. Further kinetic analysis elucidates that Onsager's classical theory substantially overestimates field-induced enhancement of ion pair dissociation in molecular electrolytes. This discrepancy arises from solvent-mediated dynamical pathways and field-induced dielectric decrement that suppress ion pair dissociation within explicit solvents, highlighting that a faithful description of molecular details is essential. Our results provide a molecular interpretation of nonlinear electrolyte transport beyond continuum theories and establish a general framework for quantifying nonequilibrium reaction kinetics in condensed phase systems.

Abstract Dilute-solution models based on the Nernst–Planck equations are commonly used for describing ion transport in flow-battery electrolytes, yet they fail to accurately capture the behaviour at the high ion concentrations typical of these systems. To overcome this limitation, we develop a concentrated-solution theory model for a multispecies electrolyte using the Stefan–Maxwell framework. Our focus is the ternary aqueous electrolyte employed in soluble-lead flow batteries, consisting of a solution of lead methanesulfonate, Pb(CH3SO3)2, in methanesulfonic acid, CH3SO3H. Molecular dynamics simulations and laboratory experiments are combined to fully parametrise this model. A Green–Kubo approach is used to compute Stefan–Maxwell diffusivities from MD data (see [D. R. Wheeler and J. Newman, J. Phys. Chem. B, 108, 18353 (2004)]). In combination with experiment, this leads to analytic expressions for density, kinematic viscosity, and the six independent Stefan-Maxwell diffusivities describing the system. Agreement between the molecular dynamics simulations and experiments is achieved using only three physically justified fitting parameters. The methodology provides a rigorous framework for parametrising continuum-physics models of multispecies electrolytes derived from concentrated solution theory and is readily adaptable to other electrochemical sys-
tems.

The lack of clear guidance for designing novel aqueous electrolytes with wide electrochemical stability window (ESW) and strong resistance to hydrogen evolution reactions (HER) has hindered the development of safe and energetic aqueous batteries (ABs). Despite advancing scientific discovery by uncovering complex patterns, machine learning remains challenging for electrolyte design, owing to intricate additive formulations, solvation interactions, and coupled performance metrics, demanding chemically interpretable workflows. Herein, a multilevel artificial intelligent (AI) framework is developed for accelerated electrolyte design for ABs. The multi-task neural network is first applied to establish the elemental features of aqueous electrolytes with wide ESW, followed by a classification-regression model to identify additives with strong HER inhibition effect. Unsupervised learning combined with molecular dynamics simulations further provides a chemical explanation. Particularly, the elaborated additives with large polar topological structures reduce HER activity and expand ESW by enhancing the water confinement effect. As a proof of concept, experimental analyses further validate the long lifespan, evidenced by symmetric-cell cycling beyond 1100h and more than 2500 cycles in Zn||VO2 full cells, along with the reliable operation of a 1.66Ah punch-type device. This multilevel AI framework integrated with experimental validations should accelerate and rationalize the development of ABs.

Activating four-electron iodine chemistry in zinc-iodine (Zn-I2) batteries promises higher energy density, yet remains challenged by polyiodide shuttling and the instability of high-valence I+ species. Here, we demonstrate that a customized NH4Cl-based aqueous electrolyte, coupled with an ion-replenishing Cl-functionalized covalent organic framework (COF-Cl) interlayer, enables long-lived four-electron Zn-I2 batteries. The optimized electrolyte promotes I+-Cl- complexation, while the COF-Cl interlayer immobilizes polyiodides and continuously releases Cl- to stabilize I+ against hydrolysis, collectively ensuring reversible I-/I0/I+ redox conversion. In situ spectroscopic and theoretical analyses reveal accelerated high-valence redox kinetics and strong I+/polyiodide interactions. As a result, the optimized cell delivers high energy density (278Wh kg- 1), fast kinetics (128 mAh g- 1 at 10 A g- 1), and remarkable cycling durability over 45000 cycles at -5°C with an ultralow decay rate of 0.00039% per cycle, with the strategy further validated in pouch cells under low-temperature conditions. This work establishes an effective ion-replenishing interlayer-electrolyte strategy for robust, high-energy aqueous Zn-I2 batteries.

A combined study of electrochemical characterization, scanning electron microscopy, gas sorption, and solid-state nuclear magnetic resonance spectroscopy was conducted to understand the effect of polymeric binder on the performance of supercapacitor electrodes. We show that increasing the quantity of PTFE binder in the carbon electrode decreases the gravimetric capacitance. The decrease in capacitance is caused by the decrease in porosity of the carbon electrode, as determined by gas sorption and NMR spectroscopy. Importantly, 19F NMR reveals the significant intrusion of the PTFE binder into the carbon micropores, evidenced through the observation of a nucleus-independent chemical shift. 23Na NMR of aqueous electrolyte adsorption further shows that increasing the quantity of the PTFE binder hinders the amount of Na+ ions adsorbed within the pores, affecting the charge storage mechanism. To mitigate this effect, an alternative dry electrode processing method was investigated, which revealed a substantial reduction in PTFE pore intrusion. The reduced pore intrusion leads to excess PTFE accumulating in the intergranular gaps, which diminishes electrochemical performance in aqueous electrolytes. Summarizing, our study reveals the significant intrusion of polymeric binder into the pores of carbon electrodes, which decreases porosity and the corresponding charge storage performance. These findings may guide the design of new electrode formulations, such as a dry process, with improved energy storage capacities.

The reversibility of Zn deposition/stripping in aqueous zinc metal batteries (ZMBs) is governed by the interfacial kinetics and unstable electrolyte-metal chemistry. Here we introduce a hybrid-entropy (HE) electrolyte that leverages entropy-driven solvation restructuring to tailor the Zn2+ coordination environment and interfacial thermodynamics. By amplifying the entropy contribution, quantified through Boltzmann's equation, HE electrolyte diminishes the Gibbs free energy of the system, thermodynamically minimizing chemical-potential gradients that promote interfacial heterogeneity. This entropic modulation triggers the spontaneous formation of an inorganic-organic composite interphase on the Zn surface, which homogenizes ion flux and shifts the Zn nucleation behavior from instantaneous to progressive modes, enabling dense and dendrite-free metal growth. These coupled mechanisms confer improved anode reversibility, delivering a cycling lifetime exceeding 3000h in Zn||Zn symmetric cells and high Coulombic efficiency of 99% over 1000 cycles in Zn||Cu cells. Consequently, practical NaV3O8||Zn pouch cells with a capacity of 1.38 Ah under high mass loading and low negative-to-positive capacity ratio (N/P) ≈ 4.2 demonstrate stable operation for over 30 days at 2.0 mA·cm-2 with negligible capacity decay. This work highlights controllable entropy engineering as an effective design principle for aqueous electrolytes and charts a viable route toward durable, high-performance ZMBs.

A novel approach for calculating the interaction energy and electrostatic force between charged spherical colloidal particles in aqueous electrolyte solutions is proposed. The formulation is based upon an integration of the McCartney-Levine force approach in an appropriately modified nonlinear Poisson-Boltzmann equation. The resulting analytical expression for the electrostatic force provides a framework capable of accurate predictions across a wide spectrum of ionic concentrations-from dilute to high ionic strength-without requiring empirical parameter adjustments. Compared to existing approaches, the present formulation demonstrates superior consistency with experimental data for monovalent salts (NaCl and KCl), successfully capturing interaction energies at both short and intermediate separation distances under high ionic strength conditions, thus providing a useful tool for handling colloidal interactions in fields such as materials science and colloid chemistry.

Gel polymer electrolytes (GPEs) are key components in electrochemical energy-storage devices, as they simultaneously serve as ion-conducting media and separators. However, their performance is often limited by the trade-off between mechanical robustness and ionic conductivity, which becomes particularly problematic in highly concentrated aqueous electrolytes due to electrolyte-induced dimensional instability. Here, we report a composite GPE based on a rigid aramid nanofiber (ANF) network coated with a hydrophilic poly(vinyl alcohol) (PVA) layer, designed for compatibility with water-in-salt electrolyte systems. The ANF scaffold provides a high-modulus framework for dimensional stability, while hydrogen-bonding interactions at the ANF-PVA interface enable effective stress redistribution without significantly impeding ion transport. The ANF-PVA composite hydrogel was impregnated with a lithium chloride-based water-in-salt electrolyte to form a GPE and subsequently coated onto activated-carbon-decorated carbon-fiber electrodes to fabricate supercapacitors. The resulting devices exhibit stable electric double-layer capacitive behavior, reliable rate capability, and excellent cycling stability over a wide temperature range from -20 to 50 °C, together with scalable electrochemical performance upon increasing device length. These results highlight the effectiveness of composite polymer-network engineering for mechanically robust and ionically efficient aqueous GPEs suitable for low-temperature energy-storage applications.

Fibrous energy-storage systems serve as a core component in the next-generation flexible and wearable electronics, yet their practical application is hindered by the limited temperature resilience of aqueous electrolytes and the mechanically fragile electrolyte-electrode interfaces. Herein, we design an in situ deep-eutectic hydrogel electrolyte based on a hydroxyl-rich glycerol-ethylene glycol-H2O system, in which the hydrogen-bond network is engineered to modulate the chemical potential of water and the free-energy landscape governing phase transitions. Strong H2O-H2O H-bonds are converted into a more uniformly distributed weak H-bond network in the electrolyte, thereby reducing the thermodynamic driving force for ice formation at low temperatures while suppressing H2O volatilization at elevated temperatures. Meanwhile, in situ photopolymerization enables the direct formation of a conformal hydrogel layer on the electrode surface, improving interfacial adhesion and mitigating parasitic reactions such as hydrogen evolution and Zn corrosion. Benefiting from the coupled thermodynamic and interfacial regulation, Zn||PANI coin cell exhibits stable operation over an ultrawide temperature range of -50°C-100°C and delivers a cycling life exceeding 10000 cycles with 86.71% capacity retention at 25°C. A fibrous Zn||PANI cell further maintains reliable cycling for over 500 cycles at -25°C, demonstrating the applicability of this strategy for temperature-resilient wearable energy-storage systems.