Lithium Cations Research Articles

Role of excited states in helium-like ions on high-order harmonic generation

We theoretically investigate high-order harmonic generation (HHG) of helium (He), lithium cation (Li+), and beryllium dication (Be2+) using the time-dependent Hartree–Fock method to solve the three-dimensional time-dependent Schrödinger equation. It is found that the intensity of the HHG increases significantly from a certain harmonic order below the ionization threshold, and the initial position of the enhancement does not depend on the intensity or the wavelength of the driving laser field. Further analysis shows that excited states play an important role on this enhancement, consistent with the excited-state tunneling mechanism [Phys. Rev. Lett. 116 123901 (2016)]. Our results unambiguously show that excited-state tunneling is essential for understanding the enhancement of HHG. Accordingly, a four-step model is herein proposed to illustrate the multiphoton excitation effect in helium-like ions, which enriches the physics of HHG enhancement.

New Hydrophilic Derivatives of Lasalocid and Their Complexes with Selected Metal Cations.

Two new esters of lasalocid, that are more hydrophilic, with glucose (LasGlu) and xylitol (LasX), have been synthesized, and their complexation of monovalent cations has been studied by various spectrometric and spectroscopic methods, such as ESI mass spectrometry, 1H, 13C NMR and FT-IR. Analyses of the results confirmed the synthesis of new esters with good yields. In order to carry out further studies, it was necessary to purify them using "flash" liquid chromatography. It was confirmed that the newly obtained molecules, as well as their complexes with lithium, sodium and potassium cations, were stabilized by a strong system of intramolecular hydrogen bonds. It was found that the hydroxyl groups of esters derived from xylitol and glucose were also involved in the complexation of cations. The results of the PM6 semiempirical calculations permitted determination of the heat of formation (HOF), and visualization of the structure of the new esters and their complexes with the cations studied. All computation results are in agreement with the spectroscopic data.

Development of a Quality Index to Evaluate the Impact of Abiotic Stress in Saline Soils in the Geothermal Zone of Los Negritos, Michoacán, Mexico

In recent years, salinity-induced soil quality impairment and the misuse of management practices have led to the reduced productivity of agroecosystems. This has prompted a search for simple and effective agricultural management strategies that improve the sustainability of agricultural production through soil quality assessments. In this context, the objective of this study was to establish an integrated soil quality index (SQI) by assessing the influence of different types of abiotic stress in two different seasons, using physical, chemical and biological indicators at three sites in the geothermal zone of “Los Negritos”, Michoacán, Mexico. Thirty-nine indicators related to soil fertility attributes and C, N, P, and S cycling—identified as the total dataset (TDS)—were evaluated. Principal component analysis (PCA) and the Spearman correlation matrix (r2 ≥ 0.6) were used to calculate the SQI using an integrated quality index (IQI) equation, with the indicators total nitrogen (TN), cation exchange capacity (CEC), lithium (Li), and zinc (Zn) identified as the minimum dataset (MDS). Significantly higher SQI values related to the better performance of soil functions were detected during the rainy season.

Enhancing Electrochemical CO2 Reduction on Perovskite Oxide for Solid Oxide Electrolysis Cells through In Situ A-Site Deficiencies and Surface Carbonate Deposition Induced by Lithium Cation Doping and Exsolution.

Solid oxide electrolysis cells (SOECs) hold enormous potential for efficient conversion of CO2 to CO at low cost and high reaction kinetics. The identification of active cathodes is highly desirable to promote the SOEC's performance. This study explores a lithium-doped perovskite La0.6- x Lix Sr0.4 Co0.7 Mn0.3 O3-δ (x = 0, 0.025 0.05, and 0.10) material with in situ generated A-site deficiency and surface carbonate as SOEC cathodes for CO2 reduction. The experimental results indicate that the SOEC with the La0.55 Li0.05 Sr0.4 Co0.7 Mn0.3 O3-δ cathode exhibits a current density of 0.991 A cm-2 at 1.5V/800°C, which is an improvement of ≈30% over the pristine sample. Furthermore, SOECs based on the proposed cathode demonstrate excellent stability over 300 h for pure CO2 electrolysis. The addition of lithium with high basicity, low valance, and small radius, coupled with A-site deficiency, promotes the formation of oxygen vacancy and modifies the electronic structure of active sites, thus enhancing CO2 adsorption, dissociation process, and CO desorption steps as corroborated by the experimental analysis and the density functional theory calculation. It is further confirmed that Li-ion migration to the cathode surface forms carbonate and consequently provides the perovskite cathode with an impressive anti-carbon deposition capability, as well as electrolysis activity.

Electrolyte contact changes nano-Li4Ti5O12 bulk properties via surface polarons

It is of general interest to combine the faradaic processes based high energy density of a battery with the non-faradaic processes based high power density of a capacitor in one cell. Surface area and functional groups of electrode materials strongly affect these properties. For the anode material Li4Ti5O12 (LTO), we suggest a polaron based mechanism that influences Li ion uptake and mobility. Here we show electrolytes containing a lithium salt induce an observable change in the bulk NMR relaxation properties of LTO nano particles. The longitudinal 7Li NMR relaxation time of bulk LTO can change by almost an order of magnitude and, therefore, reacts very sensitively to the cation and its concentration in the surrounding electrolyte. The reversible effect is largely independent of the used anions and of potential anion decomposition products. It is concluded that lithium salt containing electrolytes increase the mobility of surface polarons. These polarons and additional lithium cations from the electrolyte can now diffuse through the bulk, induce the observed enhanced relaxation rate and enable the non-faradaic process. This picture of a Li+ ion equilibrium between electrolyte and solid may help with improving the charging properties of electrode materials.

Speciation and Photoluminescent Properties of a 2,6‐Bis(pyrrol‐2‐yl)pyridine in Three Protonation States

Abstract2,6‐Bis(pyrrol‐2‐yl)pyridines are important building blocks for supramolecular assemblies and photoluminescent main group and transition metal compounds. Sterically encumbered 2,6‐bis(5‐(2,4,6‐trimethylphenyl)‐3‐phenyl‐1H‐pyrrol‐2‐yl)pyridine, H2MesPDPPh, can adopt monomeric and dimeric structures in the solid state and in solution, controlled by competing inter‐ and intramolecular hydrogen bonds. Deprotonation in the presence of lithium cations provides Li2MesPDPPh, which can be isolated in monomeric and dimeric forms depending on solvent polarity. Protonation of H2MesPDPPh disrupts intramolecular hydrogen bonding and provides the monomeric pyridinium salt [H3MesPDPPh]Cl. Independent of solvent polarity, all three derivatives exhibit intense fluorescence in solution. The absorption and emission spectra are highly sensitive to the level of protonation, which can be rationalized by the effects of (de)protonation on the HOMO and LUMO of the tricyclic π‐system.

Three-dimensional experimental-scale phase-field modeling of dendrite formation in rechargeable lithium-metal batteries

This paper presents a phase-field based numerical study on the 3D formation of dendrites due to electrodeposition in an experimental-scale lithium metal battery. Small-scale 3D simulations were firstly conducted to elucidate the characteristics and resolution requirements of the numerical framework. Using a four-fold anisotropy model to simulate the growth of lithium deposition, the dependency of dendrite morphology on charging conditions (ϕb=−0.7V and ϕb=−1.4V) on a (larger) experimental-scale metal anode was demonstrated. The dendrite shape was found to shift from a smoother, tree-like formation at the lower applied voltage, to a more spike-like, highly branched structure at the higher voltage. The resulting morphological parameters, such as dendrite propagation rates, volume-specific area, and side branching rates, were compared against published experimental data and found to be comparable to the reported ranges for the electrodeposition of spike- or tree-like metal dendrites. This finding supports our previous observation that dendrite formation is connected to the competition between the lithium cation diffusion and electric migration, generating an uneven distribution of Li+ on the electrode surface. This observation also gives insight into dendrite inhibition strategies focusing on enhancing the diffusion of lithium ions to achieve a more uniform concentration field on the anode surface.

A DFT study of COF-1 covalent organic framework as a disposable platform for rechargeable lithium-ion battery anodes

We considered the COF-1 covalent organic framework in the present study to develop materials with significant cell voltage in LIBs technology. Our analyses and evaluations based on the density functional study showed that the Li+ cation had a more stable interaction with the considered COF-1 than the neutral Li metal. Due to the adsorption of Li and Li+ on the surface of COF-1, the energy levels of HOMO and LUMO decreased drastically so that the adsorption of the lithium atom has a more significant influence on the energy gap of COF-1 than the adsorption of lithium cation. The value of the cell voltage was estimated to be 0.72 V. By increasing the number of Li/Li+ up to 6, a cell voltage of 3.34 V and a storage capacity of 169.68 mAhg−1 was obtained. The current study results described here may contribute to improving the cell voltage of the LIBs.

Enhanced Energy Storage in Lithium-Metal Batteries via Polymer Electrolyte Polysulfide-Polyoxide Conetworks.

The present article entails a novel concept of storing extra energy in a multifunctional polymer electrolyte membrane (PEM) beyond the storage capacity of a cathode, which is achieved by so-called "prelithiation" upon simply deep discharging to a low potential range of a lithium-metal electrode (i.e., -0.5 to 0.5 V). This unique extra energy-storage capacity has been realized recently in the PEM consisting of polysulfide-co-polyoxide conetworks in conjunction with succinonitrile and LiTFSI salt that facilitate complexation via ion-dipole interaction of dissociated lithium ions with thiols, disulfide, or ether oxygen of the conetwork. Although ion-dipole complexation may increase the cell resistance, the prelithiated PEM provides excess lithium ions during oxidation (or Li+ stripping) at the Li-metal electrode. Once the PEM network is fully saturated with Li ions, the remaining excess ions can move through the complexation sites at ease, thereby affording not only facile ion transport but also extra ion-storage capacity within the PEM conetwork. Of particular interest is that the lithiated polysulfide-co-polyoxide polymer network-based PEM exhibits a high conductivity of 1.18 × 10-3 S/cm at ambient, which can also store extra energy with a specific capacity of about 150 mAh/g at a 0.1C rate in the PEM voltage range of 0.01-3.5 V in addition to 165 mAh/g at 0.2C of an NMC622 (nickel manganese cobalt oxide) cathode (i.e., 2.5-4.6 V) with a Coulombic efficiency of approximate unity. Moreover, its Li-metal battery assembly with an NMC622 cathode exhibits a very high specific capacity of ∼260 mAh/g at 0.2C in the full battery range of 0.01-5 V, having a higher Li+ transference number of 0.74, suggestive of domination by the lithium cation transport relative to those (0.22-0.35) of organic liquid electrolyte lithium-ion batteries.

Adaptable platform for trapped cold electrons, hydrogen and lithium anions and cations

Cold cations, electrons and anions are ubiquitous in space, participate in star formation chemistry and are relevant to studies on the origin of molecular biology homochirality. We report on a system to generate and trap these species in the laboratory. Laser ablation of a solid target (LiH) facing a sublimating Ne matrix generates cold electrons, anions, and cations. Axial energy distributions (of {{{{{{rm{e}}}}}}}^{-}, {{{{{{rm{H}}}}}}}^{pm } and {{{{{{rm{Li}}}}}}}^{pm }) peaked at 0–25 meV are obtained in a Penning trap at 90 mT and 0.5 eV barrier. Anions can be guided and neutralized with low recoil energy by near–threshold photodetachment. An immediate prospect for this {{{{{{rm{H}}}}}}}^{-} source is to load hydrogen atoms into the ALPHA antihydrogen trap at CERN toward direct spectroscopic comparison of both conjugated species beyond 13 significant figures. The production is potentially scalable and adaptable to different species including deuterium and tritium, relevant for neutrino mass and fusion research.

Hydration and Mobility of Alkaline Metal Cations in Sulfonic Cation Exchange Membranes.

The interconnection of ionogenic channel structure, cation hydration, water and ionic translational mobility was revealed in Nafion and MSC membranes based on polyethylene and grafted sulfonated polystyrene. A local mobility of Li+, Na+ and Cs+ cations and water molecules was estimated via the 1H, 7Li, 23Na and 133Cs spin relaxation technique. The calculated cation and water molecule self-diffusion coefficients were compared with experimental values measured using pulsed field gradient NMR. It was shown that macroscopic mass transfer is controlled by molecule and ion motion near sulfonate groups. Lithium and sodium cations whose hydrated energy is higher than water hydrogen bond energy move together with water molecules. Cesium cations in possession of low hydrated energy are directly jumping between neighboring sulfonate groups. Cation Li+, Na+ and Cs+ hydration numbers (h) in membranes were calculated from 1H chemical shift water molecule temperature dependences. The values calculated from the Nernst-Einstein equation and the experimental conductivity values were close to each other in Nafion membranes. In MSC membranes, calculated conductivities were one order of magnitude more compared to the experimental ones, which is explained by the heterogeneity of the membrane pore and channel system.

Preparation and Characterization of N,N′‐Dialkyl‐1,3‐propanedialdiminium Chlorides, N,N′‐Dialkyl‐1,3‐propanedialdimines, and Lithium N,N′‐Dialkyl‐1,3‐propanedialdiminates

AbstractWe describe convenient preparations of N,N′‐dialkyl‐1,3‐propanedialdiminium chlorides, N,N′‐dialkyl‐1,3‐propanedialdimines, and lithium N,N′‐dialkyl‐1,3‐propanedialdiminates in which the alkyl groups are methyl, ethyl, isopropyl, or tert‐butyl. For the dialdiminium salts, the N2C3 backbone is always in the trans‐s‐trans configuration. Three isomers are present in solution except for the tert‐butyl compound, for which only two isomers are present; increasing the steric bulk of the N‐alkyl substituents shifts the equilibrium away from the (Z,Z) isomer in favor of the (E,Z), and (E,E) isomers. For the neutral dialdimines, crystal structures show that the methyl and isopropyl compounds adopt the (E,Z) form, whereas the tert‐butyl compound is in the (E,E) form. In aprotic solvents all four dialdimines (as well as the lithium dialdiminate salts) adopt cis‐s‐cis conformations in which there presumably is either an intramolecular hydrogen bond (or a lithium cation) between the two nitrogen atoms.

Understanding Lithium-Ion Dynamics in Single-Ion and Salt-in-Polymer Perfluoropolyethers and Polyethyleneglycol Electrolytes Using Solid-State NMR

Lithium metal batteries with high energy densities can enable a revolution in energy storage and accelerate shifts in electric transportation and electricity generation. However, several morphological and electro-chemo-mechanical challenges impede their development. Solid-state electrolytes such as those based on polymers show great promise in replacing liquid electrolytes in lithium metal batteries. Polyether-based polymer electrolytes are the most investigated but are plagued by low room-temperature ionic conductivity and poor oxidative stability. Hence, there is great need for the development and understanding of ion transport in new classes of polymer electrolytes. Perfluoropolyether (PFPE)-based electrolytes have shown improved oxidative stability, but little is understood about their lithium solvation and transport mechanism. In this work, we use multinuclear solid-state magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy to investigate the lithium cation environment and mobility in crosslinked single-ion and salt-in-polymer PFPE electrolytes and compare it directly to that of well-known polyethylene glycol (PEG) electrolytes. We show that the interaction of the lithium cation with the polymer backbone is weaker in PFPE systems compared to PEG, likely resulting in stronger ion pairing in the PFPE systems. Line shape analyses show lower lithium mobility in PFPE electrolytes despite lower activation energies being derived from spin-lattice relaxation (T1) measurements as compared to those for the PEG systems. The rapid relaxation is instead ascribed to the local fluctuations caused by polymer backbone mobility. By studying different modes of ion binding (single-ion vs salt-in-polymer), we show that differences across polymer backbones (PFPE vs PEG) have a greater effect on mobility than differences in ion binding modes within each polymer class (especially when single-ion conducting site density is not high). Our ability to use MAS NMR to study polymer electrolytes in their native state opens new opportunities to develop and understand novel polymer or hybrid solid-state electrolytes for next-generation lithium metal batteries.

Transmembrane fluxes during electrolysis in high salinity brines: Effects on lithium and other raw materials recovery

During the production of high purity lithium salts, magnesium and calcium will readily crystalize as either carbonates or hydroxides if their concentrations have not been depleted to below 2 ppm. Magnesium and calcium can be fully abated electrochemically by production of hydroxide anions via water electrolysis. While brine alkalization within an electrochemical reactor has shown great performance at proof-of-concept level, this is not feasible at industrial scale. Solids cannot be produced, nor accumulated within a water electrolyzer, and membrane fouling must be avoided at all costs. An alternative is to work on a brine that has been fully depleted from multivalent cations and produce an increase in pH beyond the needs for successful crystallization of the hydroxides. In this way, the super alkaline brine can be used as an external precipitating agent that does not dilute the other key components of the brine, namely lithium cations. We have studied the competing ion migration between chloride and hydroxide anions across an anion exchange membrane in a water electrolyzer as a function of current density. The most important differences were observed in the magnitude of the changes in the solution volumes. While water electrolysis and electro-osmotic effects were identified as processes contributing to these changes, only classical osmosis is responsible for the differential effects. In the range of study, applied current density values from 80-225 A m−2 produced higher hydroxide concentrations, although no current density values were identified to produce remarkable changes in the energy efficiency. Beyond pH 14, the passage of hydroxide across the membrane becomes faster than that of chloride.

Li+ intercalation current generation in amorphous and crystalline MoS2: Experiment and theory

In this work, crystalline and amorphous nano-MoS2 materials for effective Li+-intercalation current generation have been synthesized. The effect of disordering on the structural and electrochemical properties of nano-MoS2 has been systematically investigated by multiple characterizations: transmission electron microscopy (TEM), X-ray diffraction method and electrochemical measurements. Thermodynamic and kinetic peculiarities of intercalation processes have been studied. Dependences of the change in Gibbs’ free energy of the intercalation reaction on the extent of ‘guest’ lithium loading are analyzed. The distinctive feature of disordered structures is their ability to show colossal lithium ‘guest’ load, which ensures the specific capacity of the material in cathode processes up to ~2500 mAh·g-1 under the discharge not less than 2.6 V relative to lithium. The diffusion coefficient of lithium cations in the structure of disordered nano-MoS2 is two orders of magnitude higher than that in the crystalline MoS2. A quantum-mechanical model of the observed phenomena is suggested.

Direct molten-salt electro-reduction of CO2 in porous electrodes

Although the direct electro-reduction of CO2 is thermodynamically favorable, it is difficult to accomplish due to the limited solubility of CO2 in oxide-free molten salts. Thus, the electrochemical reduction of CO2 in molten carbonate should be assisted by the existing lithium and alkaline earth cations that alter the thermodynamic energy barrier of CO32−. In this study, we employ a porous metal foam electrode to realize the direct electro-reduction of CO2 in molten Na2CO3-K2CO3. The porous electrode increases the contact area between the solid electrode and CO2 gas, resulting in the direct electro-reduction of CO2 to CO and carbon through the thin electrolyte layer. The overall current efficiency reaches 90% for CO at 800 °C. The molten Na2CO3-K2CO3 makes the downstream product separation easy because Na2CO3 and K2CO3 are highly soluble in water. Overall, using the gas electrode achieves the direct electro-reduction of CO2 and the use of lithium- and alkaline-earth-metal-free molten carbonates, offering a more energy-efficient CO2 reduction path.

Mobility of Li+, Na+, and Cs+ cations in Nafion membrane, as studied by NMR techniques

The local mobility and diffusion of Li+, Na+, and Cs+ cations in Nafion 117 membrane were explored by 7Li, 23Na, and 133Cs spin relaxation and pulsed field gradient NMR techniques. It was shown that the macroscopic mass transfer of cations is controlled by ion motion near sulfonate groups. Lithium and sodium cations, whose hydrated energy is higher than the water hydrogen bond energy, are moving together with water molecules, but cesium cations possessing a low hydrated energy are jumping directly between the neighboring sulfonate groups.

Open-Cage Fullerene as a Selective Molecular Trap for LiF/[BeF

The insertion of ionic compounds into open-cage fullerenes is a challenging task due to the electropositive nature of the cavity. The present work reports the preparation of an open-cage C60 derivative with a hydroxy group pointing towards the centre of the cavity, which can coordinate to a metal cation, thus acting as a bait/hook to trap the metal cation such as the lithium cation in neutral LiF and the beryllium cation in the cationic [BeF]+ species. Other metal salts could not be inserted under similar conditions. The structure of MF in the cage was unambiguously determined by single-crystal X-ray diffraction. Owing to its tendency to undergo polycoordination, Li+ monomer salts have not been isolated before, despite extensive research on Li bonds. The present results provide a unique example of a Li bond.

Open‐Cage Fullerene as a Selective Molecular Trap for LiF/[BeF]+

AbstractThe insertion of ionic compounds into open‐cage fullerenes is a challenging task due to the electropositive nature of the cavity. The present work reports the preparation of an open‐cage C60 derivative with a hydroxy group pointing towards the centre of the cavity, which can coordinate to a metal cation, thus acting as a bait/hook to trap the metal cation such as the lithium cation in neutral LiF and the beryllium cation in the cationic [BeF]+ species. Other metal salts could not be inserted under similar conditions. The structure of MF in the cage was unambiguously determined by single‐crystal X‐ray diffraction. Owing to its tendency to undergo polycoordination, Li+ monomer salts have not been isolated before, despite extensive research on Li bonds. The present results provide a unique example of a Li bond.

Fast Li+ Transport via Silica Network‐Driven Nanochannels in Ionomer‐in‐Framework for Lithium Metal Batteries

AbstractFor the development of all‐solid‐state lithium metal batteries (LMBs), a high‐porous silica aerogel (SA)‐reinforced single‐Li+ conducting nanocomposite polymer electrolyte (NPE) is prepared via two‐step selective functionalization. The mesoporous SA is introduced as a mechanical framework for NPE as well as a channel for fast lithium cation migration. Two types of monomers containing weak‐binding imide anions and Li+ cations are synthesized and used to prepare NPEs, where these monomers are grafted in SA to produce SA‐based NPEs (SANPEs) as ionomer‐in‐framework. This hybrid SANPE exhibits high ionic conductivities (≈10−3 S cm−1), high modulus (≈105 Pa), high lithium transference number (0.84), and wide electrochemical window (>4.8 V). The resultant SANPE in the lithium symmetric cell possesses long‐term cyclic stability without short‐circuiting over 800 h under 0.2 mA cm−2. Furthermore, the LiFePO4|SANPE|Li solid‐state batteries present a high discharge capacity of 167 mAh g−1 at 0.1 C, good rate capability up to 1 C, wide operating temperatures (from −10 to 40 °C), and a stable cycling performance with 97% capacity retention and 100% coulombic efficiency after 75 cycles at 1 C and 25 °C. The SANPE demonstrates a new design principle for solid‐state electrolytes, allowing for a perfect complex between inorganic silica and organic polymer, for high‐energy‐density LMBs.