Anion Pair Research Articles

Bulky Phosphazenium Salt Controlling Chemoselective Terpolymerization of Epoxide, Anhydride and CO2: From Well‐Defined Block to Truly Random Copolymers

AbstractCopolymers with precise compositions and controlled sequences are great appealing for high‐performance polymeric materials, but their synthesis is very challenging. In this study, tetrakis[tris(dimethylamino)phosphoranylidenamino] phosphonium chloride (P5Cl) and triethylboron (TEB) were chosen as the binary catalyst to synthesize both well‐defined block and truly random poly(ester–carbonate) copolymers via the one‐pot/one‐step terpolymerization of epoxide/anhydride/CO2 under metal‐free conditions. The bulky nature of phosphazenium cation not only led to loose cation–anion pairs and enhanced the reactivity, but also provided the chain‐end an appropriate protection and improved the controllability. In particular, P5Cl/TEB with a molar ratio of 1/0.5 showed an extraordinary chemoselectivity for ring‐opening alternating copolymerization (ROAC) of cyclohexene oxide (CHO) and phthalic anhydride (PA) first and then ROAC of CHO/CO2. Thus, well‐defined block polyester–polycarbonate copolymers were synthesized by CHO/PA/CO2 terpolymerization. The chemoselectivity was easily tuned and the ROAC of CHO/PA and ROAC of CHO/CO2 occurred simultaneously with P5Cl/TEB=1/2, producing truly random poly(ester–carbonate) copolymers from CHO/PA/CO2. In addition, this P5Cl/TEB catalyst and the strategy to regulate its chemoselectivity are versatile for various anhydrides, epoxides and initiators. Thus, poly(ester–carbonate) copolymers with varying sequences, compositions, and topologies are successfully synthesized, making it possible to compare their properties and to expand their applications.

Understanding the potential of coal gangue as photocatalyst for antibiotic degradation: The role of abundant oxygen vacancies and electron-hole pairs

Coal gangue (CG) offers promising potential as a cost-effective photocatalyst for antibiotic degradation. However, current approaches do not emphasize the origin of its photocatalytic activity. This study investigates the photocatalytic activity of CG through a comparative analysis with one-pot aerobic/anaerobic calcinated CG. The potential application of CG as a photocatalyst for tetracycline (TC) decontamination in water was evaluated under dark and light. Characterization results identified anatase and kaolinite as the critical photosensitive minerals in CG. Batch removal experiments indicated that CG achieved up to 98 % TC removal at 1 g/L dosage, with most biotoxic intermediates reduced to below 0.9 mg L−1 Lethal Concentration 50 (LC50) of Fathead minnow (Pimephales promelas). Degradation pathways identified by density functional theory (DFT) and quantitative structure-activity relationship (QSAR) indicated that superoxide anion (⁎O2−) and electron-hole (e−-h+) pairs were predominant contributors to TC photodegradation. Theoretical calculations suggest that the oxygen vacancies on the CG surface can accelerate the production of ⁎O2−, while fast electron transport channels within surface hydroxyl groups facilitate e− and h+ separation. The findings of this research elucidate the origin of CG's photocatalytic activity and highlight the potential to serve as a photocatalyst for low-cost antibiotic removal, offering a promising solution for coal waste management and utilization.

Charge‐Sign‐Independent Separation of Mono‐ and Divalent Ions With Nanofiltration Membranes

AbstractAchieving precise selective separation of monovalent and divalent cations, as well as anions, is vital yet challenging in practical applications involving complex component treatments. Current membranes are typically effective for separating either cation pairs or anion pairs. To address this issue, a straightforward strategy for fabricating a nanofiltration (NF) membrane is developed that selectively permeates monovalent ions. This study focused on neutralizing the surface charge and tuning the pore size distribution of the polyamide membranes through a secondary interfacial polymerization using a zwitterionic copolymer consisting of 2‐methacryloyloxyethyl phosphorylcholine and 2‐aminoethyl methacrylate hydrochloride. The optimized NF membrane prepared in this study, with a near‐neutrally charged membrane surface and appropriate pore size distribution, demonstrates favorable performance in precisely separating monovalent and divalent ions, irrespective of the ion charge sign. The optimum NF membrane features high selectivity for both Cl−/SO42− (93) and Li+/Mg2+ (67) ion pairs, along with high water permeance of 8.5 L m−2 h−1 bar−1, making it competitive with many reported membranes. This study offers new insights into the ion‐selective mechanisms of polyamide membranes for monovalent/divalent ions and may guide the development of advanced membranes with single‐solute selectivity.

Synthesis and crystal structure of poly[[μ-chlorido-μ-(2,3-di-methyl-pyrazine)-copper(I)] ethanol hemisolvate], which shows a new isomeric CuCl(2,3-di-methyl-pyrazine) network.

Reaction of copper(I)chloride with 2,3-di-methyl-pyrazine in ethanol leads to the formation of the title compound, poly[[μ-chlorido-μ-(2,3-di-methyl-pyrazine)-copper(I)] ethanol hemisolvate], {[CuCl(C6H8N2)]·0.5C2H5OH} n or CuCl(2,3-di-methyl-pyrazine) ethanol hemisolvate. Its asymmetric unit consists of two crystallographically independent copper cations, two chloride anions and two 2,3-di-methyl-pyrazine ligands as well as one ethanol solvate mol-ecule in general positions. The ethanol mol-ecule is disordered and was refined using a split model. The methyl H atoms of the 2,3-di-methyl-pyrazine ligands are also disordered and were refined in two orientations rotated by 60° relative to each other. In the crystal structure, each copper cation is tetra-hedrally coordinated by two N atoms of two bridging 2,3-di-methyl-pyrazine ligands and two μ-1,1-bridg-ing chloride anions. Each of the two copper cations are linked by pairs of bridging chloride anions into dinuclear units that are further linked into layers via bridging 2,3-di-methyl-pyrazine coligands. These layers are stacked in such a way that channels are formed in which the disordered solvent mol-ecules are located. The topology of this network is completely different from that observed in the two polymorphic modifications of CuCl(2,3-di-methyl-pyrazine) reported in the literature [Jess & Näther (2006). Inorg. Chem. 45, 7446-7454]. Powder X-ray diffraction measurements reveal that the title compound is unstable and transforms immediately into an unknown crystalline phase.

Electroprecipitating the Sulfate Radical Anion Amplifies Electrochemiluminescence in Space and Time.

We have discovered a strategy to synthesize reactive radical salts, effectively bottling up radicals in space and time for future use. We apply this new principle to electrochemiluminescence (ECL) through the simultaneous electro-reduction of peroxydisulfate, S2O82-, and tris(bipyridine)ruthenium(II), [Ru(bpy)3]2+ in a water/acetonitrile mixture. The electrode generates a concentration profile exceeding the solubility of the cation and anion pair, promoting precipitation. After the application of a potential, leads are disconnected, and the crystals electrolessly chemiluminesce during dissolution and can be transported to other solutions for later chemiluminescence uses. Our method extends ECL hundreds of micrometers from the electrode surface and increases the ECL lifetime by orders of magnitude. Control experiments, including electron spin resonance, validate the crystallization of SO4•-, allowing detailed mechanistic insight. We demonstrate platform generalizability by precipitating a radical salt made of calcium and SO4•-, and we demonstrate the salt's ability to drive chemiluminescence. Our results emphasize the elegant chemical tenet that extremely reactive radicals can be bottled up as solids to be used as future reagents if precipitation occurs more quickly than the radical lifetime.

Supramolecular Enzyme-Peptide Gels for Localized Therapeutic Biocatalysis.

Enzyme therapeutics are often compromised by poor accumulation within target tissues, necessitating high doses that can exacerbate off-target effects. We report an injectable supramolecular enzyme-peptide gel platform for prolonged local enzyme retention in vivo . The gel is based on CATCH(+/-) ( C o- A ssembling T ags based on CH arge-complementarity), cationic and anionic peptide pairs that form β-sheet fibrils upon mixing 1 . Enzymes recombinantly fused to CATCH(-) peptide integrate into CATCH(+/-) β-sheet fibrils during assembly, resulting in an enzyme-peptide gel. Catalytically-active gels were fabricated with four disparate enzymes: CATCH(-)-NanoLuc luciferase, CATCH(-)-cutinase, CATCH(-)-uricase, and CATCH(-)-adenosine synthase A. CATCH(-)-cutinase gels demonstrated tunability of the platform, while CATCH(-)-NanoLuc gels demonstrated prolonged tissue retention relative to soluble enzyme. CATCH(-)-uricase gels resolved localized inflammation in a gout model, while CATCH(-)-adenosine synthase A gels suppressed localized lipopolysaccharide-induced inflammation. Modular and tunable enzyme content, coupled with prolonged tissue retention, establish CATCH enzyme-peptide gels as a generalizable vehicle for effective local therapeutic biocatalysis.

High quantum yield luminescence and scintillation properties of high-Ce-doped MgF2–Al2O3–B2O3 glasses and their glass structure

Ce-doped inorganic single crystals are currently used in scintillators in various instruments because of their outstanding luminescence properties. However, these crystals are expensive to manufacture and are inefficient in terms of their energy consumption. In this study, xCeF3-doped 40MgF2–20Al2O3–40B2O3 glasses (x = 0−30 mol%) were prepared by a melt-quenching method in N2 atmosphere, and their photoluminescence, scintillation, and dosimetry properties were investigated. The X-ray absorption fine edge spectroscopy of the Ce L3-edge indicated that the doped Ce exists in the form of Ce3+ ions, and that Ce4+ does not form because of the low basicity of the glass. The glasses underwent photoluminescence at 380 nm due to the 5d-4f transition of Ce3+, with a very high quantum yield of up to ∼100 % and low concentration quenching. The peak shape of the X-ray-induced luminescence was similar to that of the PL with a decay time of 110−70 ns. The light yields for gamma rays (137Cs source) were obtained from the pulse-height spectra, and the highest light yield among the present samples was 1071 photons/MeV with the energy resolution of 17 %. The thermoluminescence glow curves had peaks at 365 and 460 K and a good linear relationship existed in the range of 0.5–1000 mGy, with the dose response being comparable to that of a commercial dosimeter. The origin of the high quantum yield was probed by analyzing the glass structure using molecular dynamics simulation based on a graph neural network. A strong tendency to selectively bind cations and anion pairs was found: Mg preferably binds to F, B preferably binds to O, and Al binds to O and F, which can be explained by soft and hard acid and base theories. Because of this selectivity the glass forms fluoride- and oxide-rich domains, which seem to be responsible for the more effective dispersal of the luminescent center. The results of this study are expected to contribute to the development of glasses with enhanced photoluminescence and scintillation luminescence properties.

Catalytic effects of sodium salts with varied anionic pairs on the polymerization of liquid crystal polyesters

Catalytic effects of sodium salts with varied anionic pairs on the polymerization of liquid crystal polyesters

Imidazolium bromide based dual-functional redox mediator for the construction of dendrite-free Li-CO2 batteries

Rechargeable lithium-carbon dioxide (Li-CO2) batteries have emerged as a highly promising approach to simultaneously address energy shortages and the greenhouse effect. However, certain limitations exist in Li-CO2 batteries like high charge overpotential and unstable Li metal interface, which adversely affect the energy efficiency and cycling life. The incorporation of soluble redox mediators (RMs) has proven effective in enhancing the charge transfer between lithium carbonate (Li2CO3) and cathode, thereby substantially reducing the charge overpotential. Nevertheless, the severe shuttle effect of RMs results in the reactions with Li anode, not only exacerbating the corrosion of Li anode but also leading to the depletion of RMs and electrical energy efficiency. In this work, an organic compound containing large cation group, 1-ethyl-3-methylimidazole bromide (EMIBr) is proposed as the defense donor RM for Li anode in Li-CO2 batteries to address the above problems simultaneously. During charging, Li2CO3 oxidation kinetics can be accelerated by bromide anion pair (Br3−/Br−). Meanwhile, the cations (EMI+) are preferentially adsorbed around the protruding tips of Li anode through electrostatic interaction driven by surface free energy, forming protective layers that effectively inhibit further Li deposition at these tips, which is verified by DFT calculations. Additionally, Li dendrites growth is inhibited by the electrostatic repulsion of polar groups in EMIBr, resulting in uniform Li deposition. Consequently, a lower overpotential (∼1.17 V) and a longer cycle life (∼200 cycles) have been obtained for Li-CO2 battery incorporating EMIBr.

Supramolecular hydrogen-bonded networks formed from copper(II) carboxylate dimers.

The well-known copper carboxylate dimer, with four carboxylate ligands extending outwards towards the corners of a square, has been employed to generate a series of crystalline compounds. In particular, this work centres on the use of the 4-hydroxybenzoate anion (Hhba-) and its deprotonated phenolate form 4-oxidobenzoate (hba2-) to obtain complexes with the general formula [Cu2(Hhba)4-x(hba)xL2-y]x-, where L is an axial coligand (including solvent molecules), x = 0, 1 or 2, and y = 0 or 1. In some cases, short hydrogen bonds result in complexes which may be represented as [Cu2(Hhba)2(H0.5hba)2L2]-. The main focus of the investigation is on the formation of a variety of extended networks through hydrogen bonding and, in some crystals, coordinate bonds when bridging coligands (L) are employed. Crystals of [Cu2(Hhba)4(dioxane)2]·4(dioxane) consist of the expected Cu dimer with the Hhba- anions forming hydrogen bonds to 1,4-dioxane molecules which block network formation. In the case of crystals of composition [Et4N][Cu2(Hhba)2(H0.5hba)2(CH3OH)(H2O)]·2(dioxane), Li[Cu2(Hhba)2(H0.5hba)2(H2O)2]·3(dioxane)·4H2O and [Cu2(Hhba)2(H0.5hba)2(H0.5DABCO)2]·3CH3OH (DABCO is 1,4-diazabicyclo[2.2.2]octane), square-grid hydrogen-bonded networks are generated in which the complex serves as one type of 4-connecting node, whilst a second 4-connecting node is a hydrogen-bonding motif assembled from four phenol/phenolate groups. Another two-dimensional (2D) network based upon a related square-grid structure is formed in the case of [Et4N]2[Cu2(Hhba)2(hba)2(dioxane)2][Cu2(Hhba)4(dioxane)(H2O)]·CH3OH. In [Cu2(Hhba)4(H2O)2]·2(Et4NNO3), a square-grid structure is again apparent, but, in this case, a pair of nitrate anions, along with four phenolic groups and a pair of water molecules, combine to form a second type of 4-connecting node. When 1,8-bis(dimethylamino)naphthalene (bdn, `proton sponge') is used as a base, another square-grid network is generated, i.e. [Hbdn]2[Cu2(Hhba)2(hba)2(H2O)2]·3(dioxane)·H2O, but with only the copper dimer complex serving as a 4-connecting node. Complex three-dimensional networks are formed in [Cu2(Hhba)4(O-bipy)]·H2O and [Cu2(Hhba)4(O-bipy)2]·2(dioxane), where the potentially bridging 4,4'-bipyridine N,N'-dioxide (O-bipy) ligand is employed. Rare cases of mixed carboxylate copper dimer complexes were obtained in the cases of [Cu2(Hhba)3(OAc)(dioxane)]·3.5(dioxane) and [Cu2(Hhba)2(OAc)2(DABCO)2]·10(dioxane), with each structure possessing a 2D network structure. The final compound reported is a simple hydrogen-bonded chain of composition (H0.5DABCO)(H1.5hba), formed from the reaction of H2hba and DABCO.

Crystal structure of bis{2-[5-(3,4,5-trimethoxyphenyl)-4H-1,2,4-triazol-3-yl]pyridine}palladium(II) bis(trifluoroacetate) trifluoroacetic acid disolvate

The new palladium(II) complex, [Pd(C16H16N4O3)2](CF3COO)2·2CF3COOH, crystallizes in the triclinic space group P\overline{1} with the asymmetric unit containing half the cation (PdII site symmetry Ci ), one trifluoroactetate anion and one co-crystallized trifluoroacetic acid molecule. Two neutral chelating 2-[5-(3,4,5-trimethoxyphenyl)-4H-1,2,4-triazol-3-yl]pyridine ligands coordinate to the PdII ion through the triazole-N and pyridine-N atoms in a distorted trans-PdN4 square-planar configuration [Pd—N 1.991 (2), 2.037 (2) Å; cis N—Pd—N 79.65 (8), 100.35 (8)°]. The complex cation is quite planar, except for the methoxo groups (δ = 0.117 Å for one of the C atoms). The planar configuration is supported by two intramolecular C—H...N hydrogen bonds. In the crystal, the π–π-stacked cations are arranged in sheets parallel to the ab plane that are flanked on both sides by the trifluoroacetic acid–trifluoroacetate anion pairs. Apart from classical N/O—H...O hydrogen-bonding interactions, weak C—H...F/N/O contacts consolidate the three-dimensional architecture. Both trifluoroacetic moieties were found to be disordered over two resolvable positions with a refined occupancy ratio of 0.587 (1):0.413 (17) and 0.530 (6):0.470 (6) for the protonated and deprotonated forms, respectively.

Dual–ion symmetric hybrid supercapacitor built by vanadium oxide with expanded interlayers: The intercalation of cation–anion pair and reversible redox of anion excited by Al3+

The development of aluminum ion batteries (AIBs) is retarded by the low capacity of intercalation cathode and ineffective aluminum dissolution/deposition at Al anode. To solve the issues, benzoquinone(BQ)–preinserted hydrated vanadium oxide formulated as (BQ)0.04V2O5·0.87H2O (BQ-VO) with a large interlayer spacing of 13.3 Å was synthesized, which was used as both cathode and anode with Al(ClO4)3 acetonitrile (AN) electrolyte to fabricate a symmetric aluminum–ion supercapacitor. BQ-VO delivers a large capacity of ~152 mAh g−1 at 0.2 A g−1 in the range of 0–1.5 V, which is associated with the intercalation of ion (such as ClO4−, Al3+ or Al3+ − ClO4− pair) into BQ-VO and the reversible redox reaction of ClO4− ↔ Cl−, giving rise to a novel symmetric dual–ion hybrid supercapacitor. The reversible conversion of ClO4− ↔ Cl− is not observed in NaClO4 AN electrolyte, which is only excited by Al3+, leading to a continuous increasing capacity in the early stage of the cycling test. On the contrary, in the NaClO4 AN electrolyte, BQ-VO illustrates a surface-controlled capacitive performance with excellent cycling stability. Molecular dynamic (MD) simulations reveal that Al3+ and Na+ possess different solvation/anion sheaths, leading to different electrochemical performances of BQ-VO in the Al(ClO4)3 and NaClO4 electrolytes. The present work provides a routine to utilize the redox reaction of halide for energy storage.

Ion-pair chromatographic attribute in the retention of ammonium ion on a crown ether-based and a polysaccharide-based chiral stationary phases. Some mobile phase additives compatible with liquid chromatography-electrospray ionization-mass spectrometry

The design of the mobile phase additive useful in HPLC analysis on two types of chiral stationary phases, one based on chiral crown ether, and another based on polysaccharide derivative, was developed. CROWNPAK® CR-I, the chiral stationary phase bearing (R)- or (S)-(3,30-diphenyl-1,10-binaphtyl)-20-crown-6 (1) moiety is a useful CSP to separate primary amine enantiomers. While perchloric acid had been recommended as the mobile phase additive to attain a better separation, we have reexamined the effect of mobile phase additives and revealed that the retention of an ammonium ion is enhanced by a chaotropic or a hydrophobic anion in a water-based mobile phase like well-known ion pair chromatography in an RPLC. However, the retention was enhanced in reverse by a rather cosmotropic or a hydrophilic anion in an acetonitrile (ACN)-based mobile phase. These results looking contradictory to each other may be rationalized both in the basis of ion pair chromatography. A similar but smaller effect of pairing anion species was also observed on a polysaccharide-based CSP. Based on these findings, some types of mobile phase have been proposed and some of them were demonstrated to be compatible with liquid chromatography-electrospray ionization-mass spectrometry (ESI LC/MS).

Stable Cycling of Mg Metal Anodes by Regulating the Reactivity of Mg2+ Solvation Species

AbstractRationally designing stable nonaqueous electrolytes for Mg metal anodes demands a thorough understanding of their interfacial behaviors. Here, the critical role of cation–anion pairing in improving the cathodic stabilities of amine‐based electrolytes against solvent reduction and H2 evolution is identified. It is demonstrated that strong coordination between solvating amine groups and the Mg2+ cation facilitates the dehydrogenation of the ─NH2 group, which is mainly responsible for low reversibility during Mg metal plating and stripping. Introducing ion‐pairing into the primary solvation shell can effectively weaken the amine coordination such that its reduction is suppressed. A novel interfacial behavior regarding parasitic reaction product dissolution is also identified, which is responsible for the failure of interfacial passivation. An ion‐pairing electrolyte is developed based on a weakly‐solvated amine molecule and strongly coordinating Mg2+ salt. This electrolyte composition delivers long‐term Mg metal anode cycling with 99.6% Coulombic efficiency for 800 cycles.

Spontaneous Oxidation in Aqueous Microdroplets: Water Radical Cation as Primary Oxidizing Agent.

Exploration of the unique chemical properties of interfaces can unlock new understanding. A striking example is the finding of accelerated reactions, particularly spontaneous oxidation reactions, that occur without assistance of catalysts or external oxidants at the air interface of both aqueous and organic solutions (provided they contain some water). This finding opened a new area of interfacial chemistry but also caused heated debate regarding the primary chemical species responsible for the observed oxidation. An overview of the literature covering oxidation in microdroplets with air interfaces is provided, together with a critical examination of previous findings and hypotheses. The water radical cation/radical anion pair, formed spontaneously and responsible for the electric field at or near the droplet/air interface, is suggested to constitute the primary redox species. Mechanisms of accelerated microdroplet reactions are critically discussed and it is shown that hydroxyl radical/hydrogen peroxide formation in microdroplets does not require that these species be the primary oxidant. Instead, we suggest that hydroxyl radical and hydrogen peroxide are the products of water radical cation decay in water. The importance of microdroplet chemistry in the prebiotic environment is sketched briefly and the role of partial solvation in reaction acceleration is noted.

Spontaneous Oxidation in Aqueous Microdroplets: Water Radical Cation as Primary Oxidizing Agent

AbstractExploration of the unique chemical properties of interfaces can unlock new understanding. A striking example is the finding of accelerated reactions, particularly spontaneous oxidation reactions, that occur without assistance of catalysts or external oxidants at the air interface of both aqueous and organic solutions (provided they contain some water). This finding opened a new area of interfacial chemistry but also caused heated debate regarding the primary chemical species responsible for the observed oxidation. An overview of the literature covering oxidation in microdroplets with air interfaces is provided, together with a critical examination of previous findings and hypotheses. The water radical cation/radical anion pair, formed spontaneously and responsible for the electric field at or near the droplet/air interface, is suggested to constitute the primary redox species. Mechanisms of accelerated microdroplet reactions are critically discussed and it is shown that hydroxyl radical/hydrogen peroxide formation in microdroplets does not require that these species be the primary oxidant. Instead, we suggest that hydroxyl radical and hydrogen peroxide are the products of water radical cation decay in water. The importance of microdroplet chemistry in the prebiotic environment is sketched briefly and the role of partial solvation in reaction acceleration is noted.

Adsorption of Choline Phenylalanilate on Polyaromatic Hydrocarbon-Shaped Graphene and Reaction Mechanism with CO2: A Computational Study.

The interaction of ionic liquids (ILs) with carbon materials is of fundamental importance in several areas of materials science, physics, and chemistry. Their adsorption on pristine and N-doped graphene surfaces is discussed here on the basis of results of density functional theory calculations. The nature of adsorption was investigated for an amino acid (AA)-based IL consisting of the choline cation [Ch] and the l-phenylalanilate anion [Phe] that interacts with a sheet of N-doped graphene. The interaction mechanism, binding energy, electron density, and non-covalent interaction analysis were evaluated by considering the cation, anion, and ion pair adsorbed on graphene separately. The distribution of cations and anions in the liquid bulk and on the graphene surface was then analyzed by molecular dynamics simulations. Since AA-based ILs are efficient absorbents for capture of CO2 due to the pronounced affinity of carbon dioxide to react with amino groups, we investigated the capacity of [Ch][Phe] to react with CO2 under various conditions. We considered the multistep mechanism of the reaction of [Phe] with CO2 first for the anion in the liquid bulk and then for the [Phe] anion adsorbed on the graphene surface. The initial step, the formation of the zwitterionic addition product, is followed by its structural rearrangement through intramolecular proton transfer and conformational isomerization processes to form carboxylic acid derivatives. The entire mechanism was evaluated for the [Phe] anion before and after adsorption on graphene to investigate how interactions with surfaces of carbon materials can affect the CO2 capture capacity of an AA-based IL such as [Ch][Phe].

A study on the extension of correlation functions obtained from molecular dynamics simulations by the Ornstein–Zernike theory for modeled molten salts

We extend the correlation functions obtained by molecular dynamics (MD) simulation for a molten salt modeled as a superposition of the Lennard-Jones (LJ) and Coulomb potentials using the hybrid closure method, which employs the Ornstein–Zernike (OZ) theory coupled with a closure relation. An appropriate distance for switching the short-range MD part and the long-range OZ part is determined by monitoring the isothermal compressibility, excess internal energy, and pressure. The Kobryn–Gusarov–Kovalenko (KGK) closure relation is mainly employed for the hybrid closure method (MD–KGK hybrid closure). The hybrid closure with either the hypernetted chain (HNC) or Kovalenko–Hirata (KH) closure was also tested to confirm that the performance was almost equivalent to one another among the MD–HNC, MD–KH, and MD–KGK methods. The bridge function for the model molten salt is extracted using the MD–KGK hybrid closure method. At a high-density state, the bridge function shows a steep increase in the repulsive core region, as is often observed for simple fluids, whereas when the density is relatively low, the bridge function for the cation–anion pair shows a downward-sloping behavior. Furthermore, the accuracies of excess internal energy, pressure, and isothermal compressibility were also examined for the HNC, KH, and KGK approximations. For molten salt systems, these approximations exhibited a similar behavior to those for monatomic LJ fluids, especially in the high-density state. The analysis of the integrand for excess internal energy and pressure is also discussed.

Enabling High-Performance All-Solid-State Batteries via Guest Wrench in Zeolite Strategy.

All-solid-state batteries with a high energy density and safety are desirable candidates for next-generation energy storage applications. However, conventional solid electrolytes for all-solid-state batteries encounter limitations such as poor ionic conduction, interfacial compatibility, instability, and high cost. Herein, taking advantage of the ingenious capability of zeolite to incorporate functional guests in its void space, we present an innovative ionic activation strategy based on the "guest wrench" mechanism, by introducing a pair of cation and anion of LiTFSI-based guest species (GS) into the supercage of the LiX zeolite, to fabricate a zeolite membrane (ZM)-based solid electrolyte (GS-ZM) with high Li ionic conduction and interfacial compatibility. The restriction of zeolite frameworks toward the framework-associated Li ions is significantly reduced through the dynamic coordination of Li ions with the "oxygen wrench" of TFSI- at room temperature as shown by experiments and Car-Parrinello molecular dynamics simulations. Consequently, the GS-ZM shows an ∼100% increase in ionic conductivity compared with ZM and an outstanding Li+ transference number of 0.97. Remarkably, leveraging the superior ionic conduction of GS-ZM with the favorable interface structure between GS-ZM and electrodes, the assembled all-solid-state Li-ion and Li-air batteries based on GS-ZM exhibit the best-level electrochemical performance much superior to batteries based on liquid electrolytes: a capacity retention of 99.3% after 800 cycles at 1 C for all-solid-state Li-ion batteries and a cycle life of 909 cycles at 500 mA g-1 for all-solid-state Li-air batteries. The mechanistic discovery of a "guest wrench" in zeolite will significantly enhance the adaptability of zeolite-based electrolytes in a variety of all-solid-state energy storage systems with high performance, high safety, and low cost.

Locally Saturated Ether-Based Electrolytes With Oxidative Stability For Li Metal Batteries Based on Li-Rich Cathodes.

Li metal batteries applying Li-rich, Mn-rich (LMR) layered oxide cathodes present an opportunity to achieve high-energy density at reduced cell cost. However, the intense oxidizing and reducing potentials associated with LMR cathodes and Li anodes present considerable design challenges for prospective electrolytes. Herein, we demonstrate that, somewhat surprisingly, a properly designed localized-high-concentration electrolyte (LHCE) based on ether solvents is capable of providing reversible performance for Li||LMR cells. Specifically, the oxidative stability of the LHCE was found to heavily rely on the ratio between salt and solvating solvent, where local-saturation was necessary to stabilize performance. Through molecular dynamics (MD) simulations, this behavior was found to be a result of aggregated solvation structures of Li+/anion pairs. This LHCE system was found to produce significantly improved LMR cycling (95.8% capacity retention after 100 cycles) relative to a carbonate control as a result of improved cathode-electrolyte interphase (CEI) chemistry from X-ray photoelectron spectroscopy (XPS), and cryogenic transmission electron microscopy (cryo-TEM). Leveraging this stability, 4 mAh cm-2 LMR||2× Li full cells were demonstrated, retaining 87% capacity after 80 cycles in LHCE, whereas the control electrolyte produced rapid failure. This work uncovers the benefits, design requirements, and performance origins of LHCE electrolytes for high-voltage Li||LMR batteries.