The relentless challenges of uncontrolled zinc dendrite growth and severe interfacial side reactions pose a significant threat to the operation and reliability of aqueous zinc-ion batteries (AZIBs). To counter these challenges, this work introduces a novel multifunctional interfacial layer engineered from diatomite (DIA) on the zinc anode. The hierarchically ordered porous architecture and enhanced surface area of modified diatomite (M-DIA) serve as an ion transport channel to homogenize the Zn2+ ion flux, further suppressing dendrite formation. Meanwhile, the hydrophobic layer acts as a robust physical barrier, effectively shielding the zinc surface from the aqueous electrolyte. This concerted mechanism yields a dendrite-free morphology and exceptional corrosion resistance. Consequently, the M-DIA@Zn anode enables remarkably stable symmetric cell cycling stability over 1200 h at 2 mA cm-2 and 1500 h at 5 mA cm-2, respectively, and achieves an average Coulombic efficiency of 98.6% in asymmetric cells. When paired with a MnO2 cathode, the full cell exhibits superior capacity retention (260 mAh g-1 after 100 cycles) and outstanding rate performance. This work underscores the potential of natural diatomite as a multifunctional interface for stabilizing metal anodes, offering a promising pathway toward high-performance and durable zinc-based energy storage.

Highly concentrated aqueous electrolytes (HCAEs) offer superior energy density and stability in energy conversion and storage than their diluted counterparts, attributed to enhanced ion transport and correlated ion structures. However, their underlying structure-transport relationships remain poorly understood in wide-temperature and nanoconfinement environments. This study captures electrolyte structure and transport fingerprints shaped by environmental factors, by combining experimental characterization with first-principles molecular simulations at sub-nanometer resolution. It is revealed that ultrahigh concentration changes electrolyte electronic states and forms ion correlation networks with extensive aggregates. These alterations reduce free water content and hydrogen bond network connectivity, resulting in notable deviation from the Nernst-Einstein (NE)-predicted conductivity. This deviation is thermal-alleviated by weakening ion correlations. Nanoconfined interfaces create oscillatory-decaying distribution and heterogeneous orientation in HCAE constituents, resulting in redrawn ion correlation networks and localized NE deviations. Such transport behaviors are further modulated by synergistic thermal-interfacial constraints. Taking NE deviations as descriptors, HCAE transport, mediated by environment-reconstructed ion correlation networks, is then summarized to present threefold-hierarchical variations due to ion concentration, thermal effect, and confinement extent. This threefold-hierarchical framework is transferable among diverse electrolytes, offering a localized insight for electrolyte evaluation in electrochemical energy devices.

Practical research on the electrochemical nitrogen reduction reaction (eNRR) requires quantitative ammonia trace analysis because production rates are on the order of µg h−1 in aqueous electrolyte. This challenge is further aggravated by complex sample matrices. Ion chromatography is a powerful analytical technique for the quantitative determination of ammonium down to ppb‐concentrations, but requires matrix elimination (ME) for these kinds of sample. We developed a suppressed cation chromatography method using automated matrix neutralization and ME to quantitatively determine ammonium in 0.2 M sulfuric acid electrolyte at µg L−1 concentrations for use in NRR research. Although direct conductivity detection of cations is less sensitive than unsuppressed indirect conductivity detection, baseline noise requires suppression at these concentrations. Nonlinearity of the calibration curve became noticeable below ≈ 1 ng ammonium. A method limit of detection of 2 µg L−1 (ppbmol) for ammonium was achieved at 100 µL injection volume. Direct coupling of the electrochemical cell and IC enabled online quantification. This online measurement of ammonium in 0.2 M sulfuric acid electrolyte revealed ammonium contamination rapidly liberated from the hitherto judged negligible Nafion ionomer of the gas diffusion electrode at open circuit voltage, showing prior production rates to be likely false positives.

A safer, high performance LiMn2O4/LiTi2(PO4)3 cell enabled by aqueous electrolyte

In this research, aluminum/cobalt oxy-hydroxide (CoAl) thin films were successfully deposited using the layer-by-layer (LbL) method at RT. CoAl nanocomposites were grown on a stainless-steel substrate for 10, 20, and 30 LbL cycles. The structural analysis of CoAl was performed using X-ray diffraction and Fourier transform infrared spectroscopy analyses. The FESEM analysis revealed a three-dimensional flower-like porous nanostructure of the composite. A three-electrode system was employed for electrochemical testing, with the produced AlOOH/CoO(OH) binary composite acting as the working electrode. The electrochemical characteristics of the CoAl samples were analysed in a 1M KOH aqueous electrolyte. Among 10, 20, and 30 LbL cycles, the 20 LbL cycles nanocomposite exhibited the outstanding specific capacity of 2421 C g-1@ 5mVs-1 within a potential range of 1.4V. The nanocomposite exhibits pseudocapacitive battery-type behaviour. The remarkable electrochemical activity of the 20 LbL nanocomposite can be ascribed to the lower resistances identified in the sample through EIS analysis and the high surface area of the interconnected nanosheets that form a porous, nano flower-like structure. The combination of AlOOH with CoO(OH) contributes to an improvement in its charge storage capability.

The stability of cathode materials is a crucial factor that influence the overall performance of aqueous batteries. Electrolyte greatly influences on the stability of cathode material due to the complexed electrochemical-chemical reactions at the interfaces. Therefore, electrolyte engineering is a direct and powerful way to solve various problems at aqueous electrolyte interfaces. In this review article, we firstly summarized the fading mechanisms of different kinds of state-of-the-art aqueous battery cathodes including manganese/vanadium-based material, chalcogen and halogen materials, Prussian blue analogues, and Ni(OH)2 cathodes. Afterward, we reviewed recent progresses on electrolyte engineering on the stability of cathode materials such as bulk electrolyte modification, electrolyte additives, water-in-salt electrolytes, and hydrogel electrolytes. Finally, we proposed the issues that should be concerned in future electrolyte design for highly state aqueous battery cathodes.

HighlightsWolframite-type ZnWO4 particles were synthesized via facile co-precipitation synthesis with high purity and crystalline.The electrochemical studies were conducted in electrolyte concoction of KI + KOH and the KI percentage varied in 5, 10, 15 and 20 for optimizing the KI concentration.The results reveal that the ZnWO4 is a pseudocapacitor and at higher concentration of KI have negative effect on the electrode leading decrease in the capacitance value

Aqueous zinc (Zn) metal batteries (AZMBs) are a promising candidate for large-scale energy storage, but the issues of Zn anodes involving nonuniform Zn plating/stripping, H2 evolution, and low Zn utilization rate (ZUR) in aqueous electrolytes hinder their practical application. Herein, we report an in situ colloidal electrolyte via SO42--polycation electrostatic interaction to circumvent these challenges. Mechanistic studies reveal that the polycation-confined SO42- diffusion significantly elevates the Zn2+ transference number to 0.82, which can suppress anion-induced side reactions and minimize interfacial concentration gradients. Moreover, the polycations can form dynamic adsorption on Zn, disrupt the water's original H-bond network, and create an H2O-poor electrical double layer, which homogenizes the electric field distribution and suppresses H2 evolution on Zn. Consequently, the optimized electrolyte (Colloid-6) enables highly compact and (100)-plane-oriented Zn electrodeposits and uniform Zn stripping behavior even at 25 mAh cm-2, corresponding to 85.4% ZUR. The Zn electrodes in Colloid-6 achieve a long-term cycling life over 4200 h under 2 mAh cm-2, deep-cycling stability over 300 h under 25 mAh cm-2, and high-temperature adaptability (80 °C). Moreover, Colloid-6 with low water reactivity can inhibit the vanadium oxide cathode dissolution, thus supporting the stable operation of Zn//V2O5·nH2O full batteries under harsh conditions.

Research on activated carbon generated from biomass as a possible supercapacitor electrode material has increased in response to the growing need for sustainable energy storage solutions. Recent advancements in the synthesis, activation, and electrochemical performance of activated carbon derived from biomass are covered in this review. Carbonization and chemical activation employing agents like KOH, H₃PO₄, ZnCl₂, and CaCl₂ which have a major impact on pore structure and surface area are the usual steps in biomass activation. CaCl₂ activation creates mesoporous structures that facilitate rapid ion diffusion and enhanced capacitance, whereas KOH and ZnCl₂ activation often yield the largest surface area with dominant micropores. Electrochemical stability and electrical conductivity are further improved by nitrogen doping. The selection of electrolyte is also crucial; ionic liquid electrolytes, such EMIM-BF₄, offer greater thermal stability and broader voltage windows, while aqueous electrolytes, including H₂SO₄ and KOH, offer high capacitance because of their high ionic conductivity. Depending on the pore shape and activation technique, biomass-based carbons have been reported to have specific capacitances ranging from 250 to 450 F/g. All things considered, a successful method for creating high-performance, sustainable electrode materials for next-generation supercapacitors involves combining appropriate activation agents, heteroatom doping, and optimal electrolytes.

The development of high-performance pseudocapacitors based on conducting polymers has been severely constrained by fundamental challenges, including poor cycling stability, limited ionic accessibility, and complex multistep synthesis procedures. Here, we demonstrate a revolutionary one-pot electrodeposition approach utilizing lithium nanographenide (LNG) as a multifunctional electrolyte that simultaneously serves as supporting electrolyte, anionic dopant, and structural modifier for the electrochemical synthesis of the poly(3,4-ethylenedioxythiophene) (PEDOT) nanoarchitecture. Unlike conventional approaches requiring postsynthesis doping or complex composite fabrication, our method enables direct formation of the optimized PEDOT-nanographenide (PEDOT-NG) nanoarchitecture through a single electrochemical step. The nanographenide polyanions (NGn-) facilitate real-time polymer backbone modification through π-π stacking interactions and electrostatic doping, transitioning PEDOT from benzenoid to quinoidal structures while creating interconnected three-dimensional porous networks. The resulting PEDOT-NG nanoarchitecture achieves an exceptional specific capacitance of 259 F g-1 at 1.0 A g-1 with an outstanding cycling stability of 80.2% retention after 5,000 cycles in aqueous electrolyte─representing a significant advancement beyond current state-of-the-art PEDOT-based pseudocapacitors. This multifunctional electrolyte strategy represents a paradigm shift in pseudocapacitor electrode design, offering a scalable pathway toward high-performance energy storage devices with potential applications in electric vehicles and grid-scale energy storage.

Na3V2(PO4)3(NVP) is a promising cathode candidate for aqueous sodium-ion batteries (ASIBs), while the practical application of NVP is severely hindered by vanadium dissolution in aqueous electrolytes and electrochemical performance degradation. Herein, a high-entropy strategy was innovatively employed to synthesize Na3V1.0(Ti,Cr,Mn,Fe,Nb)1.0(PO4)3 (HE-NVP-1.0) cathode material via a facile sol-gel method. In situ X-ray diffraction confirms that high-entropy doping markedly alters the Na+ (de)intercalation mechanism, transforming the typical two-phase reaction between Na3V2(PO4)3 and Na1V2(PO4)3 into a continuous solid-solution reaction involving a series of stable intermediate phases, which effectively mitigates lattice strain and structural deterioration and results in a minimal unit cell volume change of merely 0.34% during cycling. Ex situ X-ray photoelectron spectroscopy elucidates the reversible valence transitions of V3+/V4+/V5+ and Mn2+/Mn3+ during charge/discharge, while Cr3+, Ti4+, and Nb5+ remain electrochemically inactive, constituting a stable lattice skeleton. Consequently, HE-NVP-1.0 delivers a reversible specific capacity of 56.2 mA h g-1 at 0.1 A g-1, exhibits an excellent rate capability of 80.7% at 5.0 A g-1, and retains 91.4% of its capacity after 5000 cycles. This work not only provides a novel high-entropy modification strategy to address vanadium dissolution in NVP but also opens new avenues for performance optimization of polyanion-type energy storage materials.

Inorganic salt electrolytes have been explored for developing cold-resistant aqueous energy storage devices. Current research on anti-freezing inorganic salt solutions mainly focuses on the H-bond regulation effects of individual cations or anions. The overall ionic effects (e.g., ion type, concentrations, cation hydration numbers, ion interactions, and ionic associations, etc.) on the anti-freezing properties lack a comprehensive understanding. In addition, crystallization of the salt electrolyte below the solidification point can lead to an abrupt performance failure of the energy storage device. In this work, we study the overall ionic effects of glass-forming aqueous electrolytes for enhancing their anti-freezing properties. It is found that ion pairs with more positive cationic potentials and less negative anionic potentials, cations with large coordination numbers, and anions with large ionic size and multiple H-bond sites are crucial for achieving glass-forming aqueous electrolytes with exceptional anti-freezing performance. Notably, the Ca(ClO4)2 eutectic electrolyte exhibits a pure glass transition at -122°C and maintains a visible liquid state at -85°C. A supercapacitor cell with a Ca(ClO4)2 electrolyte is operational at temperatures as low as -80°C. This study provides insightful understandings for designing glass-forming anti-freezing electrolytes with improved adaptability of aqueous energy storage devices under extremely cold conditions.

Corrosion protection with polymer composites in aqueous versus organic electrolytes

Enhanced π-conjugation and multi-electron transfer organic cathodes enabled high-performance zinc-ion storage.

ABSTRACT Substrate engineering offers a promising pathway to mitigate metal plating/stripping behaviors, among which carbon‐based architectures are particularly attractive. While over a thousand studies document carbon's efficacy in stabilizing non‐aqueous alkali metal anodes, only 14 focus on carbon substrates for Zn in static aqueous zinc metal batteries. This striking disparity arising from carbon's catalytic activity toward water splitting casts doubt on its utility. Here, by controlling surface hydrophilicity, nanostructural penetrability and interfacial affinity, we not only clarify carbon's viability for dense Zn plating via asynchronous homotopic competing hydrogen evolution reactions and a secondary micro‐sized interface, but also establish three foundational design principles for governing Zn deposition: 1) nanoscale water penetration dictates growth geometry; 2) interfacial affinity chemistry determines gas dynamics and byproduct formation; 3) temporal decoupling of HER and plating creates evolving active zones. These insights further endow unprecedented Zn reversibility under ultra‐demanding conditions on carbon substrates without suppressing HER (10 mA /10 mAh cm −2 , 99.9% CE, >3.5 Ah cm −2 cumulative capacity) and superior full‐cell cyclability under industrial conditions (2 mAh cm −2 , 14 mA cm −2 ). Our work provides a new conceptual framework for the use of carbon substrates in aqueous metal batteries, transforming a long‐perceived limitation into a design opportunity.

ABSTRACT Magnesium(Mg) metal anodes are attractive for next‐generation rechargeable cells due to their high volumetric capacity, low redox potential, elemental abundance, and intrinsic safety. Yet their reversibility is fundamentally constrained by mechanistic challenges distinct from monovalent metal anode counterparts. The divalent charge of Mg 2+ induces strong solvation, leading to large desolvation barriers, while its strong reducibility drives parasitic electrolyte decomposition. These coupled effects yield ion‐blocking passivation layers, hydrogen evolution, self‐corrosion, and morphological instability of Mg metal anodes. Building on these mechanistic insights, this review provides a mechanism‐driven perspective on Mg metal anodes: we delineate interfacial challenges in organic and aqueous electrolyte systems by dissecting the coupled roles of Mg 2+ solvation–desolvation, parasitic interfacial reactions, Mg plating/stripping kinetics, and mechanical evolution; on this basis, we articulate cross‐cutting design principles—encompassing electrolyte formulation, artificial interfacial layers, alloying strategies, and 3D host architectures—that balance suppression of parasitic pathways with efficient Mg 2+ transport. Special attention is given to contrasting kinetic bottlenecks of organic electrolyte systems with thermodynamic constraints of aqueous media, and extracting unified design principles bridging these two regimes. Finally, we outline a co‐design strategy across electrolytes, interfacial layers, and electrode architectures as a pathway toward reversible, scalable, and safe Mg metal cells.

This study examined cast AZ31 magnesium alloy and its variant containing micro-alloying elements of Y and Ca (AZXW alloy), evaluating their potential as anode materials in magnesium–air batteries. The AZXW alloy was fabricated via two manufacturing techniques: casting and extrusion. The synergistic influence of Y and Ca, in conjunction with the production procedure, on the microstructure, electrochemical characteristics, and anodic discharge behavior of the examined alloys was investigated. The addition of Y and Ca results in the formation of secondary phases that affect grain size, particle size, and distribution, as well as the electrochemical performance and discharge properties of the Mg–air battery constructed for this study, over 24 h or until fully discharged. This work demonstrates the potential to enhance discharge performance and electrochemical behavior by adjusting the aqueous electrolyte solution in the battery through the incorporation of Citric Acid (C.A) at varying concentrations. The incorporation of citric acid into the aqueous electrolyte improves battery stability and specific energy as long as citric acid is present in the solution. Magnesium hydroxide (Mg(OH)2) begins to form on the anode surface as its concentration progressively decreases due to complexation with dissolved magnesium ions. This diminishes the effective anode area over time, ultimately resulting in the distinctive “knee-type” collapse characteristic of electrolytes containing citric acid.

The advancement of aqueous zinc metal batteries (ZMBs) is constrained by intrinsic interfacial issues in aqueous electrolyte systems. Here, using numerical simulation, we decipher the multi-scale causes of interfacial instability, elucidating the synergistic effect of macroscopic ineffective regions and microscopic passivation. Based on the analysis, we develop an electrolyte-triggered interphase construction strategy to resolve the interfacial failure. This strategy couples the in situ formation of hydrogel interphase on both the anode and cathode with the electrolyte filling process, thereby (1) facilitating contact between electrodes and the separator; (2) promoting anode reversibility through inducing a bilayer SEI that enhances Zn2+ desolvation kinetics and blocks electron tunneling; (3) ensuring long-term cathode cycling stability via restricting the irreversible dissolution of MnO2 and side-reactions. The resultant Zn metal anode exhibited a near-unity Coulombic efficiency (99.5%) for Zn plating/stripping at an extremely low current density of 0.1mAcm-2 and the Zn/MnO2 full cell sustained 2000 full-duty-cycles with an exceptionally low decay rate of 0.0051% per-cycle. This work unlocks an alternative anglefor promoting practical ZMBs toward more sustainable energy storage systems.

Uncontrolled proton activity in aqueous electrolytes triggers detrimental side reactions that compromise the stability of zinc (Zn) metal anodes. To address this challenge, we propose a full-process proton regulation strategy enabled by the unique β-1,4-glycosidic framework of chitosan oligosaccharide (COS). The rigid COS backbone effectively constrains proton generation and transport in the electrolyte, while its preferential interfacial adsorption constructs an ultrathin molecular barrier that inhibits proton consumption at the Zn surface. This dual-function molecular architecture synergistically realizes "generation-transport-consumption" proton regulation, thereby delivering exceptional electrochemical performance: long-term cycling stability over 8,000 h in Zn||Zn symmetric cells, an average Coulombic efficiency of 99.84% over 2,300 cycles in Zn||Cu cells, and superior cycling stability for more than 2,000 cycles at 2 A g-1 in Zn||MnO2 full cells. This work reveals glycosidic frameworks as a universal and transferable design principle for aqueous batteries, shifting electrolyte design from functional group-centric optimization to framework-enabled regulation toward sustainable, high-performance energy storage.

The development of reversible metal anodes is a key challenge for advancing aqueous battery technologies, particularly for scalable and safe stationary energy storage applications. Here we demonstrate a strategy to realize epitaxial electrodeposition of iron (Fe) on single-crystal copper (Cu) substrates in aqueous electrolytes. We compare the electrodeposition behavior of Fe on polycrystalline and single-crystalline Cu substrates, revealing that the latter enables highly uniform, dense, and crystallographically aligned Fe growth. Comprehensive electron backscatter diffraction and X-ray diffraction analyses confirm the formation of Fe with specific out-of-plane and in-plane orientations, including well-defined rotational variants. Our findings highlight that epitaxial electrodeposition of Fe can suppress dendritic growth and significantly enhance the Coulombic efficiency during plating/stripping cycles. This approach bridges fundamental crystallography with practical electrochemical performance, providing a pathway toward high-efficiency aqueous batteries utilizing Earth-abundant materials.