Formation Of Cluster Ions Research Articles

Effects of Hydrogen Dissociation During Gas Flooding on Formation of Metal Hydride Cluster Ions in Secondary Ion Mass Spectrometry.

The application of hydrogen flooding was recently shown to be a simple and effective approach for improved layer differentiation and interface determination during secondary ion mass spectrometry (SIMS) depth profiling of thin films, as well as an approach with potential in the field of quantitative SIMS analyses. To study the effects of hydrogen further, flooding of H2 molecules was compared to reactions with atomic H on samples of pure metals and their alloys. H2 was introduced into the analytical chamber via a capillary, which was heated to approximately 2200 K to achieve dissociation. Dissociation of H2 up to 30% resulted in a significant increase in the intensity of the metal hydride cluster secondary ions originating from the metallic samples. Comparison of the time scales of possible processes provided insight into the mechanism of hydride cluster secondary ion formation. Cluster ions presumably form during the recombination of the atoms and molecules from the sample and atoms and molecules adsorbed from the gas. This process occurs on the surface or just above it during the sputtering process. These findings coincide with those of previous mechanistic and computational studies.

Effect of succinonitrile on the structural, ion conductivity, and dielectric properties of PVDF‐HFP based solid polymer electrolytes

AbstractA detailed account of the poly(vinylidene difluoride‐co‐hexafluoropropylene) (PVDF‐HFP)/succinonitrile (SN)/lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) based solid polymer electrolytes (SPEs) of various compositions is reported. SN is incorporated as plasticizer, while LiTFSI is employed as the source of lithium ions. Fourier transfer infrared (FTIR) spectroscopy reveals the formation of polar and electroactive γ crystal phase by PVDF in pristine PVDF‐HFP and the prepared SPE films. FTIR further confirms the interaction between the host polymer and the salt and between the salt and the plasticizer. The interaction between the salt and plasticizer suggests that SN not only offers the plasticization effect but also facilitates salt dissociation. The ion conductivity increases with increasing salt content up to 20 wt% but beyond that concentration a decline in ion conductivity is observed, which could be attributed to the ion pair association or cluster formation due to the excess salt concentration that reduces the availability of free ions and ultimately leads to the reduction in ion conductivity. After including SN in the SPE formulation, electrochemical impedance spectroscopy reveals a substantial increase in room temperature ion conductivity of the SPE from ~1.08 × 10−5 S cm−1 for pristine SPE with 20 wt% salt to ~2.7 × 10−4 S cm−1 for plasticized SPE with 40 wt% SN and 20 wt% salt. This is attributed to the plasticizing effect of SN that enhances ion mobility through the matrix and to the increased charge carrier concentration (SN facilities salt dissociation). The fabricated SPEs exhibit a significant enhancement in ion conductivity with increasing temperature and the maximum ion conductivity of 1.1 × 10−3 S cm−1 is attained at 393 K by plasticized SPE with 40 wt% SN content. The ion conductivity of all the prepared SPEs follows the temperature dependent Arrhenius behavior, suggesting the thermally activated ion hopping mechanism of ionic conduction. Further, the plasticized SPEs display near unity ion transference number indicating the predominance of the ionic mode of conduction. The dielectric and electric modulus analysis reveal a faster relaxation phenomenon and hence higher ion conductivity of the prepared SPEs with increasing salt and plasticizer content.

Investigating the ions emitted by multiply charged ionic liquids from a porous electrospray ion source

A porous electrospray ion source was tested with three ionic liquids in order to investigate the effects of ionic liquid properties on the sizes of ion clusters emitted by purely ionic electrospray sources. Two of the ionic liquids, bis(1-ethyl-3-methylimidazolium) tetrathiocyanatocobaltate and 1,6-bis(3-methylimidazolium-1-yl)hexane bis(trifluoromethylsulfonyl)amide, were selected due to them having a dication or dianion, which were termed multiply charged ionic liquids due to them containing anions or cations with more than one charge within them. These were selected in order to investigate ionic clustering within electrospray ion emission and were compared against one of the most common ionic liquids, EMI-BF4. The current–voltage data showed that EMI-BF4 emitted similar levels of current to bis(1-ethyl-3-methylimidazolium) tetrathiocyanatocobaltate, even though the latter liquid had significantly lower conductivity and higher viscosity, suggesting an improvement in current speculated to be due to the extra charges contained by the ions. Time-of-flight and retarding potential analysis data are provided, showing all three liquids emitting ions comprising of monomers, dimers, trimers, and quadramers, with some of the 1,6-bis(3-methylimidazolium-1-yl)hexane bis(trifluoromethylsulfonyl)amide data showing heavier species emission. The data also suggested that the multiply charged ionic liquids produced ions that have two anions or cations attached, termed “double ions,” with these ions not been previously reported using porous electrospray sources. Furthermore, it was found that the dimers emitted by both of the multiply charged ionic liquids seemed to be more stable than EMI-BF4 dimers, providing insight into ion cluster formation.

Generation of seed electrons in guided ionization waves in He–O2 mixtures: The effect of negative ion cluster formation

The kinetics of electrons and negative ions was numerically studied under the conditions, which are typical for multi-pulsed guided ionization waves in He flows ejected into ambient air. It was shown that, in He with a small admixture of O2 or air, O2− ions formed due to three-body electron attachment in the discharge afterglow are rapidly converted to O4− cluster ions in pulse off time. We suggested that seed electrons are generated at the leading edge of a pulse in two steps, and these steps are dissociation of O4− ions to form O2− ions followed by electron detachment from the O2− ions. The rate of O4− dissociation was calculated in He–O2 mixtures for various reduced electric fields on the basis of a Monte Carlo simulation. This rate, as well as the rate of electron detachment from O2− ions calculated previously, was used to simulate seed electron generation in a high-voltage nanosecond pulse in He–O2 mixtures for different gas pressures. It was shown that the formation of O4− ions drastically hinders the generation of seed electrons in multi-pulsed guided ionization waves in He–O2 and He–air mixtures.

Effect of one- and two-dimensional nanomaterials on polysulfone-based anion exchange membranes for fuel cells

To investigate nanoparticle morphology's impact on the performance of composite anion exchange membrane (AEM), one-dimensional quaternized branched polyethyleneimine @multi-walled carbon nanotubes (QBPEI@MWCNTs) and two-dimensional quaternized branched polyethyleneimine @graphene oxide sheets (QBPEI@GO) were prepared and incorporated into quaternized polysulfone (QPSF) matrices to form QQ-x-MWCNTs and QQ-x-GO AEMs. These AEMs exhibited superior mechanical properties due to the flexible QBPEI cross-linking and nanoparticle reinforcement. Moreover, QBPEI facilitated microphase separation and ion cluster formation along the surface of nanoparticles, enhancing OH− transport. As a result, QQ-1.0%-MWCNTs and QQ-0.7%-GO AEMs both showed high ionic conductivity (83.19 mS/cm and 76.14 mS/cm at 80 °C). QQ-x-MWCNTs AEMs displayed higher conductivity than QQ-x-GO AEMs over the entire temperature range (20–80 °C) at the same level of ion exchange capacity. QQ-0.7%-MWCNTs AEM excelled, achieving a peak power density of 102.44 mW/cm2 in an H2/O2 fuel cell (80 °C, 40 % RH), surpassing QQ-0.5%-GO AEM (86.50 mW/cm2). Evidently, one-dimensional MWCNTs are effective for establishing long-range interconnected ion transport channels, making them excellent AEM fillers.

Cation valency in water-in-salt electrolytes alters the short- and long-range structure of the electrical double layer

Highly concentrated aqueous electrolytes (termed water-in-salt electrolytes, WiSEs) at solid-liquid interfaces are ubiquitous in myriad applications including biological signaling, electrosynthesis, and energy storage. This interface, known as the electrical double layer (EDL), has a different structure in WiSEs than in dilute electrolytes. Here, we investigate how divalent salts [zinc bis(trifluoromethylsulfonyl)imide, Zn(TFSI)2], as well as mixtures of mono- and divalent salts [lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) mixed with Zn(TFSI)2], affect the short- and long-range structure of the EDL under confinement using a multimodal combination of scattering, spectroscopy, and surface forces measurements. Raman spectroscopy of bulk electrolytes suggests that the cation is closely associated with the anion regardless of valency. Wide-angle X-ray scattering reveals that all bulk electrolytes form ion clusters; however, the clusters are suppressed with increasing concentration of the divalent ion. To probe the EDL under confinement, we use a Surface Forces Apparatus and demonstrate that the thickness of the adsorbed layer of ions at the interface grows with increasing divalent ion concentration. Multiple interfacial layers form following this adlayer; their thicknesses appear dependent on anion size, rather than cation. Importantly, all electrolytes exhibit very long electrostatic decay lengths that are insensitive to valency. It is likely that in the WiSE regime, electrostatic screening is mediated by the formation of ion clusters rather than individual well-solvated ions. This work contributes to understanding the structure and charge-neutralization mechanism in this class of electrolytes and the interfacial behavior of mixed-electrolyte systems encountered in electrochemistry and biology.

The impact of sodium lauryl sulfate on hydrogen evolution reaction in water electrolysis

This study confirms the sodium lauryl sulfate (SLS) surfactant is effective to enhance water electrolysis performance especially when combined with NaCl. The water electrolysis experiment on different concentrations of SLS and SLS-NaCl mixture electrolyte were performed. The results indicate the presence of NaCl is more effective to enhance the SLS containing electrolyte performance instead of adding more SLS concentration. More SLS concentration is effective to enhance hydrogen evolution reaction (HER) when NaCl is added. The effectiveness of NaCl is shown by the order of final HER SLS 0.5 M + NaCl 3.9212 × 10−7 Mol. L−1, SLS 0.3 M + NaCl 3.8789 × 10−7 Mol. L−1, and, SLS 0.5 M 3.6758 × 10−7 Mol. L−1. The SLS creates positively charged micelles which increases ion mobility and HER. The NaCl accelerates the HER due to the formation of smaller ion clusters that react more quickly with the cathode. Therefore, this study reveals the mechanism of electrolysis enhancement by surfactant mixed electrolyte.

Investigation of ion association kinetics in Na2SO4-H2O by excess Raman spectroscopy and 2D correlation Raman spectroscopy

The ion association of salts aqueous solutions have long captivated the attention of researchers within the field of physical chemistry. In this paper, we have performed a comprehensive analysis of ion interactions in sodium sulfate (Na2SO4) aqueous solutions using a combination of high-resolution techniques, including excess (ERS) and two-dimensional correlation (2DCRS) Raman spectroscopy in conjunction with molecular dynamics (MD) calculations. The Raman spectrum shows that two inflection points in the Raman shift of the O–H vibration are observed with the increase in Na2SO4 concentration. Simultaneously, a new peak of the SO42- vibration appears at first inflection point, representing the formation of ion association. Further analysis based on ERS and 2CRS reveals that these two inflection points correspond respectively to the formation of ion pairs (CIPs) and small ion clusters. Importantly, MD simulations confirm the above experimental results. Our study provides evidence for ion association and clustering in aqueous in salt ion aqueous solutions.

Eco-sustainable design of seawater sea-sand slag-based geopolymer mortars incorporating ternary solid waste

This study aimed to explore the feasibility of utilizing geopolymer as alternatives to Ordinary Portland Cement (OPC) in marine engineering. Eco-friendly seawater sea-sand slag-based geopolymer mortars (SS-SGMs) were prepared by blending seawater, sea-sand, Basalt Fibres (BF), Polypropylene Fibres (PPF), and ternary solid waste. The effects of activator modulus, alkaline content, water-to-binder ratio, and the volume fractions of BF and PPF on the mechanical performance, environmental impact, and cost of SS-SGMs were researched using the L16(4)5 Taguchi orthogonal method. Three evaluation methods were used to assess the impact of the different factors. First, the influence of a single factor was analyzed using methods of range and variance analysis. Subsequently, three new evaluation metrics were proposed to consider the synergistic effects of mechanical performance, environment, and cost. Finally, a Gray-Technique of Ordering Preferences by Similarity to Ideal Solution (Gray-TOPSIS) model was established, and the influence weights of each factor were proposed, thereby determining the optimal solution in a multi-index evaluation system. The recommended optimal mix proportion for SS-SGMs was determined as follows: activator modulus of 1.0, alkaline content of 4%, water-to-binder ratio of 0.42, PPF volume fraction of 0.4%, and BF volume fraction of 0.3%. Compared to OPC with the same strength grade, SS-SGMs demonstrated similar costs, a reduction in carbon emissions by approximately 75–83%, a decrease in energy consumption by around 50–67%, and lower drying shrinkage than traditional geopolymer. Under the influence of seawater, the products of SS-SGMs were capable of forming chloride-ion adsorbing products like hydrotalcite and Brucite. Additionally, the formation of C4AH13 and ion clusters can enhance the matrix density, thereby improving the mechanical performance of SS-SGMs.

A Flexible and Mechanical Robust All-Solid-State Polymer Electrolyte with Microphase Separated Structure for Lithium-Ion Battery.

Polyethylene oxide (PEO)-based electrolytes are the most widely used solid polymer electrolyte (SPE) due to their high safety, excellent ability to dissociate lithium salts, low cost, and ease of preparation. However, low ionic conductivity and narrow electrochemical stability window limit their potential for further development. "Polymer-in-salt" electrolytes exhibit superior electrochemical performance; however, the high lithium salt concentration makes the SPE mechanically fragile when facing lithium dendrites. Therefore, preparing an SPE that can withstand a high concentration of lithium salt while still maintaining good mechanical properties has become a valuable challenge. In this study, a macroscopically homogeneous but nanoscopically phase-separated polymer matrix was designed as an electrolyte that can withstand a high concentration of lithium salt while retaining good mechanical properties, and this study investigated changes in the Li+ solvation structure within the electrolyte and analyzed the reasons for the simultaneous achievement of good ionic conductivity (1.02 × 10-3 S cm-1 at 60 °C) and mechanical properties (7 MPa at room temperature). The formation of large ion clusters at the phase interface and selective enrichment of lithium salt in specific regions are found to play crucial roles, and the critical current density (CCD) can reach a value of 2.2 mA cm-2. This work demonstrates a promising design approach for polymer electrolytes that achieves an optimal balance between SPE conductivity and mechanical properties through microstructure control.

Enhancing proton exchange membrane water electrolysis by building electron/proton pathways

Proton exchange membrane water electrolysis (PEMWE) plays a critical role in practical hydrogen production. Except for the electrode activities, the widespread deployment of PEMWE is severely obstructed by the poor electron-proton permeability across the catalyst layer (CL) and the inefficient transport structure. In this work, the PEDOT:F (Poly(3,4-ethylenedioxythiophene):perfluorosulfonic acid) ionomers with mixed proton-electron conductor (MPEC) were fabricated, which allows for a homogeneous anodic CL structure and the construction of a highly efficient triple-phase interface. The PEDOT:F exhibits strong perfluorosulfonic acid (PFSA) side chain extensibility, enabling the formation of large hydrophilic ion clusters that form proton-electron transport channels within the CL networks, thus contributing to the surface reactant water adsorption. The PEMWE device employing membrane electrode assembly (MEA) prepared by PEDOT:F-2 demonstrates a competitive voltage of 1.713 ​V under a water-splitting current of 2 ​A ​cm−2 (1.746 ​V at 2A cm−2 for MEA prepared by Nafion D520), along with exceptional long-term stability. Meanwhile, the MEA prepared by PEDOT:F-2 also exhibits lower ohmic resistance, which is reduced by 23.4 ​% and 17.6 ​% at 0.1 ​A ​cm−2 and 1.5 ​A ​cm−2, respectively, as compared to the MEA prepared by D520. The augmentation can be ascribed to the superior proton and electron conductivity inherent in PEDOT:F, coupled with its remarkable structural stability. This characteristic enables expeditious mass transfer during electrolytic reactions, thereby enhancing the performance of PEMWE devices.

Thermodynamics of interactions and structural peculiarities of interpenetrating polymer networks based on polyurethane and copolymer of 2-hydroxyethyl methacrylate with methacryloyloxyethylphosphorylcholine

Interpenetrating polymer networks based on biocompatible components – polyurethane and copolymer of 2-hydroxyethyl methacrylate with methacryloyloxyethylyphosphorylcholine (HEMA-MPC) were synthesized and thermodynamic parameters of interactions in the system and morphology were investigated. The thermodynamic parameters of interactions between polymer components of the IPNs were calculated based on sorption isotherms of methylene chloride vapors by samples of the created polymer systems. It is shown that MPC plays the role of a compatibilizer in the system, increasing the thermodynamic compatibility between polyurethane and the HEMA-MPC copolymer at small amounts of the copolymer in the IPNs. As the amount of copolymer HEMA-MPC in the IPNs increases, the value of the free energy of the polyurethane and copolymer mixing shifts to the positive value, which is associated with the formation of ionic clusters of MPC. This may mean that with an increasing amount of the MPC in the system, interactions between the negatively charged phosphoryl groups and the positively charged nitrogen atom of various MPC polymer chains occur, i.e., the part of intermolecular interactions (polyurethane and copolymer) decreases, while the part of intramolecular interactions (between different groups of MPC) increases. The results of the morphology investigations of the IPN samples are consistent with the data of the thermodynamic compatibility study of polymers during the formation of the IPNs. With a significant increase in the positive values of the free energy of the polyurethane and copolymer mixing in the IPNs with 41 % and 51 % of the copolymer content, a significant phase separation is observed in the IPNs, with phase inclusions ranging from 1 to 5 mm.

Hg-Hg bonding and its influence on the stability of (HgS)n clusters.

Pulsed laser ablation of a HgS(s) precursor shows the formation of small cluster ions, (HgS)n=2-4+, together with HgSn=1-8± and [(HgS)n + Sm]±. The computed structure, atomization energy, and HOMO-LUMO gap energy values of the lowest energy ring singlet show stable (HgS)n=2-8. However, the computed bond conductance of the Hg-Hg bond in (HgS)n shows a high value for (HgS)n=2-4 (ξ = 1.072-0.122), whereas it is low for (HgS)n=5-8 (ξ = 0.039-0.006) and decreases significantly as the ring expands, indicating that (HgS)n≥5 is unstable. It evidences that the weak chemical bonding between Hg2+-Hg2+ closed shell (5d10-5d10) electrons plays a significant role in the stability of ring (HgS)n=2-4. Thus, it validates the experimental observation of stable cluster ions up to (HgS)4+. In contrast, the low energy chain triplet (HgS)n=2-8 shows a progressive increase in stability and bond conductance with chain length, indicating sustained mercurophilic interactions in long chain clusters like its crystal structure. Furthermore, the lowest/low energy isomers of HgSn=1-8 have been computed for their energetics, HOMO-LUMO gaps, and electron affinity using DFT-B3LYP/PBE0 methods.

Nucleation Domains in Biomineralization: Biomolecular Sequence and Conformational Features.

Biomolecules play a vital role in the regulation of biomineralization. However, the characteristics of practical nucleation domains are still sketchy. Herein, the effects of the representative biomolecular sequence and conformations on calcium phosphate (Ca-P) nucleation and mineralization are investigated. The results of computer simulations and experiments prove that the line in the arrangement of dual acidic/essential amino acids with a single interval (Bc (Basic) -N (Neutral) -Bc-N-Ac (Acidic)- NN-Ac-N) is most conducive to the nucleation. 2α-helix conformation can best induce Ca-P ion cluster formation and nucleation. "Ac- × × × -Bc" sequences with α-helix are found to be the features of efficient nucleation domains, in which process, molecular recognition plays a non-negligible role. It further indicates that the sequence determines the potential of nucleation/mineralization of biomolecules, and conformation determines the ability of that during functional execution. The findings will guide the synthesis of biomimetic mineralized materials with improved performance for bone repair.

Eutectic Mixtures As Highly Concentrated and Molten Electrolytes with Nearly Single-Ion Conducting Behavior

Today's state-of-the-art liquid electrolytes in lithium ion batteries (LIBs) have a high ionic conductivity and good performance regarding their cycle life. (1) However, they pose a safety risk due to their high vapor pressures and low thermal stability. (1) Furthermore, due to the limited electrochemical stability of the solvent, liquid electrolytes are not suitable for the application in high-voltage LIBs. (2) Molten salts, also called ionic liquids (IL), or highly concentrated electrolytes (HCE) have high lithium ion concentrations, where nearly every solvent molecule is coordinated. Due to this, there are strong ion interactions and the formation of ion clusters that lead to an increased lithium ion transference number of >0.5. (3) Therefore, they can represent an alternative in the field of liquid electrolytes. Additionally, HCE exhibit a higher thermal and electrochemical stability compared to dilute electrolytes and can improve the cycle performance in lithium metal batteries. (4, 5)McOwen et al. reported the coordination of lithium ions and crystalline structures in HCE of the binary mixtures of ethylene carbonate (EC) and lithium bis(trifluoromethane sulfonyl)imide (LiTFSI) with molar ratio up to 1:1. (6) Based on the concept of melting point depression as known from thermodynamics, room-temperature molten, highly concentrated electrolytes of a carbonate-based solvent with lithium sulfonyl imides were investigated. Instead of EC, the solvent pinacol carbonate (PIC) without acidic α-hydrogen atoms, but four bulky methyl groups was synthesized and used for eutectic mixtures, as the melting point of PIC is with 187 °C far above room-temperature. The physicochemical properties of these electrolytes are studied with respect to the different influence of lithium bis(fluorosulfonyl)imide and LiTFSI despite their same basic molecule structure. The focus will be on the electrochemical analysis by the means of the ionic conductivity, transference number and the electrochemical stability.In comparison to dilute liquid electrolytes the molten electrolytes show extremely high transference numbers, especially for the PIC-LiTFSI mixtures nearly a single-ion conducting behavior (0.9) is observed. This behavior can be explained by the formation of a 2D polymeric network within the HCE electrolyte as determined by crystallographic measurements in the solid state. Combined with the high electrochemical stability, a stable long-term cycling and dendrite suppression in symmetric lithium cells could be shown. Cycling in full cells with high-voltage cathode materials such as LiNi0.6Mn0.2Co0.2O2 (NMC622) or LiMn4O2 (LMO) against lithium metal anodes is applicable. References K. Xu, Chemical Reviews, 104(10), 4303–4417 (2004).J. Li, C. Ma, M. Chi, C. Liang and N. J. Dudney, Advanced Energy Materials, 5(4) (2015).K. M. Diederichsen, E. J. McShane and B. D. McCloskey, ACS ENERGY LETTERS, 2(11), 2563–2575 (2017).G. Jiang, F. Li, H. Wang, M. Wu, S. Qi, X. Liu, S. Yang and J. Ma, Small Struct., 2(5), 2000122 (2021).V. Nilsson, A. Kotronia, M. Lacey, K. Edstrom and P. Johansson, ACS Applied Energy Materials, 3(1), 200–207 (2020).D. W. McOwen, D. M. Seo, O. Borodin, J. Vatamanu, P. D. Boyle and W. A. Henderson, Energy & Environmental science, 7(1), 416–426 (2014).

Response of ionizable block copolymer assemblies to solvent dielectrics: A molecular dynamics study

Ionizable copolymers assembly in solutions is driven by the formation of ionic clusters. Fast clustering of the ionizable blocks often leads to the formation of far-from equilibrium assemblies that ultimately impact the structure of polymer membranes and affect their many applications. Using large-scale atomistic molecular dynamics simulations, we probe the effects of electrostatics on the formation of ionizable copolymer micelles that dominate their solution structure, with the overarching goal of defining the factors that control the assembly of structured ionizable copolymers. A symmetric pentablock ionizable copolymer, with a randomly sulfonated polystyrene center tethered to polyethylene-r-propylene block, terminated by poly(t-butyl styrene), in solvents of varying dielectric constants from 2 to 20, serves as the model system. We find that independent of the solvents, this polymer forms a core–shell micelle with the ionizable segment segregating to the center of the assembly. The specific block conformation, however, strongly depends on the sulfonation levels and the dielectric constant and the polarity of the solvents.

Loosely coordinating diluted highly concentrated electrolyte toward −60 °C Li metal batteries

Lithium metal batteries (LMBs) promise energy density over 400 Wh kg−1. However, they suffer severe electrochemical performance deterioration at sub-zero temperatures. Such failure behavior highly correlates to inferior lithium metal anode (LMA) compatibility and sluggish Li+ desolvation. Here, we demonstrate that cyclopentylmethyl ether (CPME) based diluted high-concentration electrolyte (DHCE) enables −60 °C LMBs operation. By leveraging the loose coordination between Li+ and CPME, such developed electrolyte boosts the formation of ion clusters to derive anion-dominant interfacial chemistry for enhancing LMA compatibility and greatly accelerates Li+ desolvation kinetics. The resulting electrolyte demonstrates high Coulombic efficiencies (CE), providing over 99.5%, 99.1%, 98.5% and 95% at 25, −20, −40, and −60 °C, respectively. The assembled Li-S battery exhibits remarkable cyclic stability in −20, and −40 °C at 0.2 C charging and 0.5 C discharging. Even at −60 °C, Li-S cell with this designed electrolyte retains > 70% of the initial capacity over 170 cycles. Besides, lithium metal coin cell and pouch cell with 10 mg cm−2 high S cathode loading exhibit cycling stability at −20 °C. This work offers an opportunity for rational designing electrolytes toward low temperature LMBs.

Insights into the structure and Ion transport of pectin-[BMIM][PF6] electrolytes.

We investigate the effect of pectin on the structure and ion transport properties of the room-temperature ionic liquid electrolyte 1-n-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) using molecular dynamics simulations. We find that pectin induces intriguing structural changes in the electrolyte that disrupt large ionic aggregates and promote the formation of smaller ionic clusters, which is a promising finding for ionic conductivity. Due to pectin in [BMIM][PF6] electrolytes, the diffusion coefficient of cations and anions is observed to decrease by a factor of four for a loading of 25 wt. % of pectin in [BMIM][PF6] electrolyte. A strong correlation between the ionic diffusivities (D) and ion-pair relaxation timescales (τc) is observed such that D ∼ τc-0.75 for cations and D ∼ τc-0.82 for anions. The relaxation timescale exponents indicate that the ion transport mechanisms in pectin-[BMIM][PF6] electrolytes are slightly distinct from those found in neat [BMIM][PF6] electrolytes (D∼τc-1). Since pectin marginally affects ionic diffusivities at the gain of smaller ionic aggregates and viscosity, our results suggest that pectin-ionic liquid electrolytes offer improved properties for battery applications, including ionic conductivity, mechanical stability, and biodegradability.

Nanoconfined Water-Ion Coordination Network for Flexible Energy Dissipation Device.

Water-ion interaction in a nanoconfined environment that deeply constrains spatial freedoms of local atomistic motion with unconventional coupling mechanisms beyond that in a free, bulk state is essential to spark designs of a broad spectrum of nanofluidic devices with unique properties and functionalities. Here, wereport that the interaction between ions and water molecules in a hydrophobic nanopore forms a coordination network with an interaction density that is nearly four-fold as that of the bulk counterpart. Such strong interaction facilitates the connectivity of the water-ion network and is uncovered by corroborating the formation of ion clusters and the reduction of particle dynamics. Wedesign a liquid-nanopore energy dissipation system and demonstrate in both molecular simulations and experiments that the formed coordination network controls the outflow of confined electrolytes along with a pressure reduction, capable of providing flexible protection to personnel and devices and instrumentations against external mechanical impacts and attacks. This article is protected by copyright. All rights reserved.

Tandem Mass-Selective Cryogenic Digital Ion Traps for Enhanced Cluster Formation.

We present the implementation of tandem mass-selective cryogenic ion traps, designed to enhance the range of ion processing capabilities that can be performed prior to spectroscopic interrogation. We show that both the formation of ion clusters and mass filtering steps can be combined in a single cryogenic linear quadrupole ion trap driven by RF square waves. Mass filtering and mass isolation can be achieved by manipulation of the RF frequency and duty cycle. Very importantly, this scheme circumvents the need for high-amplitude RF voltages that can be incompatible with typical cryogenic ion processing conditions. In addition, proper adjustment of the stability boundaries during the clustering process allows for the preferential formation of a specific cluster size rather than a broad distribution of sizes. Lastly, we show that a specific cluster size can be formed, mass-selected, and then transferred to another ion trap for a second completely separate ion processing step. The instrumentation and modular design developed here expand the scope of ionic species and clusters that can be accessed by processing electrosprayed ions.