Ionic Aggregates Research Articles

Simulation of the Cation Solvation Structure of the Electrolyte in Separator Nanopores of a Lithium Ion Battery.

The solvation structure of Li+ plays a critical role in ion transport and electrochemical reactions in lithium-ion battery (LIB) electrolytes. To investigate the solvation structure and coordination number of Li+, we examined the impact of force field parameters using molecular dynamics simulations. In the system with mixed carbonates and lithium hexafluorophosphate (LiPF6), the total coordination number of Li+ is found to be primarily determined by nonbonded parameters of Li+. The polarity of carbonate partial charges significantly affects the Li+ solvation structure, and scaling down the partial charges promotes ion association. By simulating the solvation structure of carbonate electrolyte between two layers of polyethylene (PE) short chains as a model of separator nanopore, it is intriguingly found that linear carbonates tend to accumulate on the PE surface, increasing ion concentration and enhancing ion aggregation. Experimental measurements confirm that the nanoporous structure on the surface of the separator tends to shrink and close during battery cycling, and further influence the Li+ solvation structure as simulation exhibits and further impact the service performance of LIBs. This provides a new insight into the electrolyte-separator interaction on ion transport and electrochemical reactions.

Hydrogen Bonds Mediating the Structural and Dynamic Behaviors in Choline-Phenolic Acid Ionic Liquids: A Computational Investigation.

The impact of hydrogen bonds (HBs) on the structural and dynamic behaviors of choline-phenolic acid ionic liquids ([Cho][PA] ILs) was explored by using density functional theory (DFT) calculations and molecular dynamics (MD) simulations. The most stable conformation of individual [Cho][PA] ion pairs was determined, and the interactions between charged entities were characterized, indicating the existence of robust HBs between [Cho]+ and [PA]-. The bulk phase MD simulations of [Cho][PA] ILs showed that ion aggregation becomes more pronounced as more phenolic hydroxyl groups are present on [PA]-. The results further indicated that the carboxylate oxygen of [PA]- forms strong HBs with both the hydroxyl hydrogen of [Cho]+ and the phenolic hydroxyl hydrogen of [PA]-. The former type of HBs remains robust even with more phenolic hydroxyl groups attached to [PA]-, whereas the latter type increases in quantity with more phenolic hydroxyl groups, potentially driving ion aggregation and reducing the self-diffusion coefficients of both [Cho]+ and [PA]-. Our findings are expected to contribute to a fundamental understanding of how HBs affect the structural and dynamic properties of [Cho][PA] ILs, thereby facilitating their broader applications.

Linear viscoelasticity of sulfonated polystyrene ionomers based on bivalent cations

Linear viscoelasticity is analyzed for unentangled sulfonated polystyrene ionomer samples, SPS-X, neutralized with transitional bivalent metal ions (with X = Zn2+, Mn2+, Co2+, and Ni2+). Two model systems, with the degree of gelation slightly above the gel point (1.0 mol. %) and close to the full gelation point (1.6 mol. %), are chosen. For either system, the amplitude of plateau is insensitive to, while the terminal relaxation time is highly dependent on, the degree of neutralization. The terminal relaxation time first increases, but then decreases with the increase in the degree of neutralization. This trend is discussed with respect to the difference in dissociation rates between the acidic, ionic associations and free salts that coexist in the ion aggregates. The transition point, where the terminal relaxation time achieves the highest value, occurs at the stoichiometric point for Zn2+, but is higher than the stoichiometric point for Mn2+, Co2+, and Ni2+. Both the ion content at the transition point and the terminal relaxation time follow the order of SPS-Ni > SPS-Co > SPS-Mn > SPS-Zn. This order contrasts with SPS-X with alkali counterions where the transition point is consistently the stoichiometric point and the terminal relaxation time increases with the decrease in the counterion size. We attribute this order to the different filling statuses of the electrons in the 3d orbital for these SPS-X samples.

Design and Characterization of Gel Polymer Electrolytes Incorporating Highly Concentrated Electrolytes: Impact of Solidification on Bulk and Electrochemical Properties

Gel polymer electrolytes (GPEs) are considered promising candidates for next-generation lithium batteries (LIBs) due to their high ionic conductivity, shape flexibility, wide electrochemical stability window, and compatibility with electrodes. In this study, chemically cross-linked poly(ethylene oxide-co-propylene oxide)-based GPEs incorporating highly concentrated lithium bis(fluorosulfonyl)amide (LiFSA) electrolytes in ethylene carbonate (EC) were systematically investigated. The thermal properties, solvation structure, ionic transport properties, and electrochemical performance of the GPEs were evaluated by thermal analysis, Raman spectroscopy, ionic conductivity measurements, pulsed-field gradient nuclear magnetic resonance, interfacial stability tests and deposition/dissolution reversibility with metallic lithium electrode, direct-current polarization for the Li+-transference number measurements, and charge-discharge cycling with a graphite electrode. The results revealed that at high salt concentrations, Li⁺-ion transport becomes faster than FSA- and EC transport, predominantly involving contact ion pairs and aggregates. Electrochemical evaluations confirmed the formation of stable interfacial layers and good compatibility with metallic lithium. Also, high capacity and high Coulombic efficiency was demonstrated for the charge/discharge of a graphite electrode. All the revealed properties show the potential of this GPE system for safer, high-performance lithium batteries.

Polarization-Induced Breaching of the Liquid/Liquid Interface Formed with Water-in-Salt Electrolytes.

The solvation properties of water-in-salt electrolytes (WiSEs) have been extensively studied by spectroscopic and computational means and were shown to impart them with unique chemical and physical properties when compared to more classical superconcentrated aqueous solutions. More specifically, the formation of ionic aggregates in solutions containing a large concentration of TFSI anions was shown to alter the water and anion reactivity at electrochemical interfaces, often improving the performance of aqueous rechargeable batteries. However, insights into the role of the WiSE solvation structure on ion transfer at electrochemical interfaces are scarce. Herein, interfaces between two immiscible electrolytes (ITIESs) are used to study the energetics for ion transfer between aqueous LiCl and LiTFSI solutions and dichloroethane. Combining electrochemical measurements at microinterfaces with metadynamics molecular dynamics (MD) simulations, the effect of solvation properties on the energy for transferring Li+ and Cl-/TFSI- ions across the liquid/liquid interface was studied. While increasing the LiCl concentration increases the amount of ion pairs, it only marginally impacts the ion transfer energy. Instead, using large LiTFSI concentrations at which ionic aggregates are formed, ion transfer across the liquid/liquid interface shows a unique behavior that departs from that observed for polarizable or nonpolarizable interfaces. Ions do not freely cross the interface, with a transfer energy found to be ≈8-10 kcal/mol. However, upon polarization, ionic aggregates are found to breach the liquid/liquid interface, locally mixing both solutions. We believe that such a finding calls for reevaluating our current understanding of ion transfer across chemical interfaces in superconcentrated electrolytes, including liquid/liquid interfaces used in membrane-less electrochemical systems.

Ionic Associations and Hydration in the Electrical Double Layer of Water-in-Salt Electrolytes.

Water-in-Salt-Electrolytes (WiSEs) are an exciting class of concentrated electrolytes finding applications in energy storage devices because of their expanded electrochemical stability window, good conductivity and cation transference number, and fire-extinguishing properties. These distinct properties are thought to originate from the presence of an anion-dominated ionic network and interpenetrating water channels for cation transport, which indicates that associations in WiSEs are crucial to understanding their properties. Currently, associations have mainly been investigated in the bulk, while little attention has been given to the electrolyte structure near electrified interfaces. Here, we develop a theory for the electrical double layer (EDL) of WiSEs, where we consistently account for the thermoreversible associations of species into Cayley tree aggregates. The theory predicts an asymmetric structure of the EDL. At negative voltages, hydrated Li+ dominates, and cluster aggregation is initially slightly enhanced before disintegration at larger voltages. At positive voltages, when compared to the bulk, clusters are strictly diminished. Performing atomistic molecular dynamics (MD) simulations of the EDL of WiSE provides EDL data for validation and bulk data for parametrization of our theory. Validating the predictions of our theory against MD showed good qualitative agreement. Furthermore, we performed electrochemical impedance measurements to determine the differential capacitance of the studied LiTFSI WiSE and also found reasonable agreement with our theory. Overall, the developed approach can be used to investigate ionic aggregation and solvation effects in the EDL, which, among other properties, can be used to understand the precursors for solid-electrolyte interphase formation.

Development of poly(vinyl alcohol) (PVA)/magnesium salt-based solid polymer electrolytes and its electrical double layer capacitor application

Solid polymer electrolytes (SPEs) comprising poly(vinyl alcohol) (PVA)/magnesium trifluromethanesulfonate [Mg(OTf)2] were prepared by the solution casting technique. The resulting PVA/Mg(OTf)2-based SPE exhibits the maximum ionic conductivity of (3.03 ± 0.01) × 10[Formula: see text]S/cm upon addition of 40 wt.% of Mg(OTf)2. The PVA/Mg(OTf)2-based SPEs follow the Vogel–Tamman–Fulcher (VTF) theory for ionic conduction, indicating that the conduction arises from the free volume within PVA polymer chain. Besides, differential scanning calorimetry (DSC) shows a lower glass transition temperature at 55.85[Formula: see text]C after the inclusion of 40 wt.% of Mg(OTf)2. Furthermore, FTIR analysis proves the complexation between PVA and Mg(OTf)2 in the SPEs. Deconvolution studies of FTIR data are also carried out to determine the percentage of free ions, ion pairs, and ion aggregates. Moreover, the electrochemical potential window improves from 3.80 to 4.77 V with the inclusion of 40 wt.% of Mg(OTf)2. Transference number studies show that magnesium ion is the main contributor in conduction. An electrical double-layer capacitor (EDLC) was fabricated using the most conductive PVA/Mg(OTf)2-based SPE and two identical carbon-based electrodes to evaluate its electrochemical performance through cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) analysis. The resulting EDLC exhibits a specific capacitance of 305 mF/g and shows electrochemical stability up to 500 cycles of charging and discharging.

Astragenol alleviates neuroinflammation and improves Parkinson's symptoms through amino acid metabolism pathway and inhibition of ferroptosis.

Astragenol alleviates neuroinflammation and improves Parkinson's symptoms through amino acid metabolism pathway and inhibition of ferroptosis.

Green synthesis of silver-modified bacterial cellulose with enhanced antimicrobial activity for advanced biomedical application.

Green synthesis of silver-modified bacterial cellulose with enhanced antimicrobial activity for advanced biomedical application.

Directional control of the formation rate, and structural and mechanical properties of yuba films via disulfide bond- or ionic interaction-mediated soy protein aggregation.

Yuba is a worldwide popular soybean product, but its development is currently challenged by the time-consuming fabrication process. In this study, we proposed a simple yet effective strategy to enhance the formation rate and tensile strength of yuba films by introducing calcium ions and sodium metabisulfite (SM). Results show that calcium ion increased the density and continuity of the yuba films, while SM led to the formation of larger protein particles. Moreover, dynamic light scattering indicated that the size of the largest protein particles increased from 112.8 to 408.6 nm as the concentration of SM rose from 0 to 20 mmol L-1. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis results revealed a strong correlation between the formation of large protein particles and the release of basic polypeptides from glycinin (11S) during SM treatment. Furthermore, the blue shift of the maximum emission wavelengths of fluorescence intensity suggested that the exposed hydrophobic residues of the basic polypeptides became trapped inside the protein particles upon heating. The results demonstrated that the structure and functional properties of protein particles significantly impacted the formation rate and tensile strength of yuba films. These findings offer valuable and fundamental insights for the advancement of industrial production of yuba films. © 2025 Society of Chemical Industry.

Single-Ion Polymer-in-Salt Electrolytes Enabling Percolating Ionic Nanoaggregates for Ambient-Temperature Solid-State Batteries.

Solid polymer electrolytes (SPEs) with high ion conduction and interfacial stability are crucial for advancing high-performance solid-state batteries. While tuning electrolytes with weak solvation structures shows promise in enhancing interfacial stability, it remains challenging to concurrently achieve high Li+ conductivity. Herein, we introduce a single-ion polymer-in-salt (SIP-in-salt) electrolyte, which not only provides additional charge carriers and enhanced salt compatibility via an ionic polymer backbone but also forms nanometric percolating ionic aggregates (p-AGGs) at high salt concentrations. Unlike state-of-the-art weak solvation structures, p-AGGs are found to be homogeneous, interconnected, and possess enhanced Li+-anion dissociation, allowing structural diffusion over reduced distances and continuous Li+ transport pathways. The SIP-in-salt electrolyte enables a 100-fold improvement in Li+ conductivity compared to traditional polymer-in-salt electrolytes, lowering the operational temperature of SPE-based solid-state batteries to 25 °C. This work demonstrates a promising strategy for advancing SPEs by tuning ionic solvation structures, paving the way for next-generation high-performance batteries.

Electron Beam Irradiation’s Effect on Polyaniline/LiClO4/CuO Nanocomposite: A Study of Dielectric, Conductivity and Electrochemical Properties

A straightforward chemical polymerization process was used to create the polyaniline/LiClO4/CuO nanoparticle (PLC) nanocomposite, which was then exposed to varying doses of electron beam (EB) radiation and studied. The FESEM, XRD, FTIR, DSC, TG/DTA, and electrochemical measurements with higher EB doses showed clear changes. The FTIR spectra of the PLC nanocomposite showed variations in the C-N and carbonyl groups at 1341 cm−1 and 1621 cm−1, respectively. After a 120 kGy EB dose, the shape changed from a smooth, uneven surface to a well-connected, nanofiber-like structure, creating pathways for electricity to flow through the polymer matrix. The EB irradiation improved the thermal stability by decreasing the melting temperature, and the XRD and DSC studies reveal that the decrease in crystallinity is attributed to the dominant chain scission mechanism. The enhanced absorption and red shift in the wavelength (from 374 nm to 400 nm) observed in the UV-Visible spectroscopy were caused by electrons transitioning from a lower to a higher energy state, with a progressive drop in the band gaps (Eg) from 2.15 to 1.77 eV following irradiation. The dielectric parameters increased with the temperature and electron beam doses because of the dissociation of the ion aggregates and the emergence of defects and/or disorders in the polymer band gaps. This was triggered by chain scission, discontinuity, and bond breaking in the molecular chains at elevated levels of radiation energy, leading to an augmented charge carrier density and, subsequently, enhanced conductivity. The cyclic voltammetry study revealed an enhanced electrochemical stability at a high scan rate of about 600 mV/s for the PLC nanocomposite with the increase in the EB doses. The I-V characteristics measured at room temperature exhibited nonohmic behavior with an expanded current range, and the electrical conductivity was estimated, using the I-V curve, to be around 1.05 × 10−4 S/cm post 20 kGy EB irradiation.

Unveiling the structure of aqueous calcium nitrate solutions by x-ray scattering

Abstract This study investigates Ca(NO3)2 solutions across varying concentrations, revealing that Ca2+ maintains a coordination number of ∼8 whereas NO3⁻ hydration decreases with concentration. At high concentrations, NO3⁻ partially replaces water molecules in the first coordination shell of Ca2+, forming ion pairs and clusters via bidentate and monodentate coordination modes. Ion aggregation disrupts and restructures the hydrogen-bond network. These findings offer essential insights into ion–solvent interactions in concentrated electrolytes.

Fluorescence tracking of inter- and intramolecular motion in zwitterionic aggregate.

Ionic aggregates are among the most common forms of matter, yet the investigation of their molecular motion is often constrained by the instability of isolated anions and cations, as well as the lack of real-time monitoring techniques. This study presents a zwitterionic strategy that integrates both cations and anions into one fluorescent organic framework, forming a zwitterionic molecule. The zwitterionic strategy simplifies the intricate cation-anion systems that are typically found in conventional inorganic salts and imparts them with fluorescent properties, facilitating real-time tracking of ionic-interaction-induced molecular motion within ionic aggregates. Specifically, a blue shift in the fluorescence wavelength signified changes in aggregate states due to intermolecular motion, whereas a decrease in intensity was linked to intramolecular-motion-caused conformational changes. This spontaneous molecular motion enabled dynamic switching of the excited state energy-decay pathway, leading to switchable color-light responses. Overall, the zwitterionic strategy offers a novel framework for exploring the properties and behaviors of molecules in ionic aggregates.

The synergistic effect induced by "Z-bond" between cations and anions achieving a highly reversible zinc anode.

The synergistic effect induced by "Z-bond" between cations and anions achieving a highly reversible zinc anode.

Unveiling the Formation and Electrochemical Properties of Nano‐Clusters in Lithium Battery Electrolyte Induced by Nitrate Ion

LiNO3 is known to significantly enhance the reversibility of lithium metal batteries; however, the modification of solvation structures in various solvents and its further impact on the interface have not been fully revealed. Herein, we systematically studied the evolution of solvation structures with increasing LiNO3 concentration in both carbonate and ether electrolytes. The results from molecular dynamics simulations unveil that the Li+ solvation structure is less affected in carbonate electrolytes, while in ether electrolytes, there is a significant decrease of solvent molecules in Li+ coordination, and a larger average size of Li+ solvation structure emerges as LiNO3 concentration increases. Notably, the formation of large ion aggregates with size of several nanometers (nano‐clusters), is observed in ether‐based electrolytes at conventional Li+ concentration (1 m) with higher ratio, which is further proved by infrared spectroscopy and small‐angle X‐ray scattering experiments. The nano‐clusters with abundant anions are endowed with a narrow energy gap of molecular orbitals, contributing to the formation of an inorganic rich electrode/electrolyte interphase that enhances the reversibility of lithium stripping/plating with Coulombic efficiency up to 99.71%. The discovery of nano‐clusters elucidates the underlying mechanism linking ions/solvent aggregation states of electrolytes to interfacial stability in advanced battery systems.

The influence of solvent cage structure on ionic aggregate structure, and structural morphology in polyether-ester-sulfonate copolymer ionomers

All-atom molecular dynamics simulations are carried out to understand the solvation cage structure, ionic aggregate structure, and structural morphology of polyether-ester [poly(ethylene oxide), PEO, and poly(tetramethylene oxide), PTMO] sulfonate sodium copolymer ionomers. The pure PEO-Na ionomer shows weak ionic aggregates compared with pure PTMO-Na ionomer, which arises from the formation of a solvation cage structure that ethers oxygen atoms within PEO backbone chains encase ions to shield the coulombic interaction of ionic pairs. By analyzing the difference of solvation cage structure in pure PEO and PTMO-Na ionomers, the changes of ionic aggregate structure and structural morphology of copolymer ionomers upon the content of PEO and temperature are clarified. Specifically, the separated microdomains show a thermally driven mixing tendency as temperature is raised, which is attributed to thermally driven enhancing the ionic aggregates near the interface between PEO and PTMO microdomains, thereby promoting the effective compatibility of interface between PEO and PTMO microdomains. These findings provide a direct link between previous experiments about x-ray scattering [Macromolecules 45, 3962 (2012)] and rheology [Macromolecules 47, 3635 (2014)], which has significant implications for the design and optimization of single-ion conductor material properties.

Constructing Anion Solvation Microenvironment Toward Durable High-Voltage Sodium-Based Batteries.

Sodium-based rechargeable batteries are some of the most promising candidates for electric energy storage with abundant sodium reserves, particularly, sodium-based dual-ion batteries (SDIBs) perform advantages in high work voltage (≈5.0V), high-power density, and potentially low cost. However, irreversible electrolyte decomposition and co-intercalation of solvent molecules at the electrode interface under a high charge state are blocking their development. Herein, a high-salt concentration microenvironment is created and proposed by tailoring the solvation structures of charge carriers including both cations and anions, which maintains highly oxidation-resistant contact ion pairs and ion aggregates and provides a high ion conductivity. The tailored solvation structure makes a great contribution to protecting the graphite cathode from electrolyte oxidation, solvent co-intercalation, and structural degradation by constructing a robust cathode-electrolyte interphase with standout electrochemical stability. Based on this, the SDIBs achieved an excellent high-voltage cycling stability with 81% capacity retention after 10000 cycles and the battery showed an improved rate performance with 97.4 mAh g-1 maintained at 100C. It is identified that regulating anion solvation structure is responsible for the stable interface chemistry and enhanced reaction kinetics, which provides deep insight into the compatibility design between the electrolyte and specialized charge storage in electrodes.

Enhanced Charge Transport through Ion Networks in Highly Concentrated LiSCN-Polyethylene Carbonate Solid Polymer Electrolytes.

Challenging the preference for bulky anions due to low binding energy with Li+ ion, the lithium thiocyanate-polyethylene carbonate (LiSCN-PEC) solid polymer electrolyte (SPE) demonstrates higher ionic conductivities (3.16 × 10-5 S cm-1) at polymer-in-salt concentration (100 mol%) compared to those with lithium bis(fluorosulfonyl)imide (LiFSI, 1.01 × 10-5 S cm-1) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI, 1.72 × 10-7 S cm-1). Through the careful selection of PEC and LiSCN as components of SPE, the carbonyl stretching of PEC and the SCN- stretching band as vibrational reporters provide detailed structural insights into the Li+ ion transport channel. Spectroscopic investigations reveal that enhanced ion aggregation alters the solvation structure around the Li+ and diminishes the interaction between Li+ and polymer (PEC) with increasing LiSCN concentrations, promoting faster segmental motion as a major transport mechanism. However, the transition observed from subionic to superionic behavior in the Walden plot indicates the onset of segmental motion decoupled charge transport pathway. The SCN- vibrational spectrum elucidates the evolution from a Li-SCN-Li type chain-like structure to a Li2 > SCN < Li2 type extended ion network with increasing LiSCN concentration, revealing that the ion network provides an alternative channel for Li+ ion transfer at higher concentrations, enhancing conductivity.

Application of Elastomer Microsphere Particles as Water-Based Drilling Fluid Lost Circulation Material

Summary Lost circulation is a common issue during oil and gas well drilling, presenting significant safety hazards and resulting in substantial economic losses. Bridging materials typically exhibit limited deformation and poor adaptability to formation pores and fractures, primarily due to size mismatching. Polymer gel materials have the potential to address these issues effectively. While strength is a crucial factor affecting plugging performance, other properties—such as the toughness and elasticity of polymer gel particles—are often overlooked. In this research, we introduce a novel elastomer plugging material that exhibits high toughness and elasticity. The material is composed of polyampholytes, which are synthesized through the copolymerization of an acrylate monomer with long alkyl side groups and a pair of oppositely charged monomers. The acrylic monomer enhances the mobility of the polymer chain, while the oppositely charged monomer generates a gradient interaction, resulting in the formation of ionic aggregates with a broad range of sizes and stiffness. The multigradient strong interaction affords the elastomer remarkable strength and elasticity, which, in turn, safeguards the structural integrity of microsphere particles when subjected to elevated pressure and shear stress. Additionally, the presence of weak interactions, enabled by high mobility, promotes gradual energy dissipation, ultimately enhancing the toughness of the material. PABD [poly (AMPS-BXSZ-DMDAAC)] microsphere particles possess the ability to effectively plug leakage channels by infiltrating pore cracks that are smaller than their own size. Additionally, they can form an elastomer block layer to seal cracks that are larger than their own size, which is facilitated by self-healing through the accumulation of particles and the intermolecular forces between them. As the pressure increases, the plugging layer compresses and becomes more dense, thereby effectively preventing the leakage of drilling fluid into the formation. The experimental results demonstrate that PABD microsphere particles effectively obstruct 8-darcy and 180-darcy consolidated sand trays at temperatures as high as 150°C. Moreover, these particles can be used to seal unconsolidated sand beds of 40−60 mesh, and their plugging performance is significantly enhanced when combined with traditional rubber. This study emphasizes the considerable application potential of elastomer materials in drilling operations.