Lithium Ion Affinities Research Articles

Association of alkali metal cations with phosphatidylcholine liposomal membrane surface

Interactions of alkali metal cations (Li+, Na+, K+, Cs+) with phosphatidylcholine (PC) liposomal membranes were investigated through experimental studies and theoretical considerations. Using a microelectrophoresis technique, charge densities of experimental membrane surfaces were measured as a function of the pH of electrolyte solutions. Equilibria between the PC liposomal membranes and monovalent ions were mathematically analyzed and described quantitatively through a previously proposed theoretical model. Association constants between functional groups of PC and the studied ions were determined and used to define theoretical curves of membrane surface charge density versus pH. Theoretical and experimental data were compared to verify the model. The PC membrane was found to have the highest affinity for lithium ions, among the ions tested.

Promotion of reversible Li+ storage in transition metal dichalcogenides by Ag nanoclusters

After years of development, improvement in the electrochemical properties of MoS2 through structural modifications has reached its limit. Further improvements in the Li+ storage properties of MoS2 must be based on an understanding of the Li+ storage mechanism in MoS2. On this basis, we have developed a novel ternary composite of graphene, MoS2 nanosheets and a small amount (1 wt%) of silver nanoclusters (NCs; MoS2/G/Ag). The presence of the Ag NCs in the composite is, however, instrumental and serves several purposes: immobilization of sulfur, increased association with Li+ and increased spacing between graphene sheets. The presence of this small amount of Ag NCs was able to increase the Li+ storage capacity of MoS2 by 60% (with a discharge capacity of ~1300 mAh g−1 at 0.5 A g−1 compared with 800–850 mAh g−1 for a MoS2/graphene composite without the Ag NCs (MoS2/G)). The MoS2/G/Ag composite also exhibited a very impressive rate performance: discharge capacities of 1040 and 850 mAh g−1 at the very high current densities of 1 and 5 A g−1, respectively (the corresponding values from MoS2/G without the Ag NCs are 790 and 580 mAh g−1). A high-capacity alternative to graphite electrodes commonly used in lithium-ion batteries has been made by scientists in Singapore and China. Molybdenum disulfide (MoS2) has a two-dimensional layered structure resembling graphite, but with a significantly higher affinity for lithium ions. When combined with graphene, a conductive sheet-on-sheet material is formed which maintains a high capacity over many charge–discharge cycles. Jim Yang Lee and colleagues now report a way that uses silver nanoparticles to raise the lithium-ion storage of MoS2/graphene oxide electrodes even higher, by over 60%. The team employed a simple and scalable carbon monoxide reduction reaction to insert uniform layers of sub-2-nanometre silver spheres between the MoS2 and graphene sheets. The expansion in interlayer distance and the improved sulphur immobilization and lithium-ion association are likely causes for the jump in storage capacity. A minute presence of silver nanoclusters in a MoS2 nanosheet–graphene composite was found to significantly increase the reversibility of Li+ storage in the composite through Li+ association, pillaring of graphene and the immobilization of S species.

Bond energies (Pt-NH3, Pt-Cl) and proton affinity of cisplatin: A density functional theory approach

The energies of the Pt-NH3 and Pt-Cl bonds of cisplatin are calculated by means of a density functional theory method with the B3LYP functional and various basis sets. The calculated bond energies of 37.38 kcal·mol−1 and 64.35 kcal·mol−1 for Pt-NH3 and Pt-Cl, respectively, agree well with the experimental values (37.28 kcal·mol−1 and 69.31 kcal·mol−1 respectively) derived from enthalpy changes. The proton and lithium ion affinities of cisplatin are also obtained with the B3LYP functional. Structural characterizations for the protonated and lithiated cisplatin complexes are given. Protonation and lithiation alter the geometric parameters, and the gas-phase proton affinity (198.71 kcal·mol−1) is much higher than the lithium ion affinity (70.32 kcal·mol−1).

First principles investigation of electronic structure change and energy transfer by redox in inverse spinel cathodes LiNiVO4 and LiCoVO4

A first-principles investigation on changes of the crystal structure and electronic structure by lithium intercalation was performed for LiNiVO4 and LiCoVO4 with inverse spinel structures. The spin states were found to change from low spin states in the de-lithiated phases to high spin states in the lithiated phases, correlated with the decrease in the octahedral crystal field splitting caused by lithium intercalation. Atomic basin population analysis combined with differential charge density analysis showed that the charge transfer caused by lithium intercalation reduces both the transition metal ions and the oxygen ions, simultaneously weakening the covalent-bonding between them. To obtain a deeper insight into the energy transfer process, the lithiation process was analyzed by considering contributions from the electronic part and ionic part, defined as electron affinity and lithium ion affinity, which costs and releases energy in the lithiation process, respectively. The electron affinity of the host was found to be characteristic of the redox potential while the lithium ion affinity is almost the same for these two cathodes. The 3d electron configuration of the transition metal ions is the dominant factor determining the redox potential although the transition metal ions and the oxygen ions are both reduced. For the host material with d5, d6, and d7 configurations, our results reveal a Λ-shape for the electron affinity, with the maximum at the d6 configuration, and correspondingly a V-shape for the reduction potential, with the minimum at the d6 configuration.

Probing the Influence of Anomeric Effects on the Lithium Ion Affinity in 1,3-Diaza Systems: A Computational Study

Lithium ion affinities of methanediamine (MDA), N,N,N',N'-tetramethylmethanediamine (TMMDA), 1,3-diazacyclohexane (DAC), trans-3,5-diazabicyclo[4.4.0]decane (trans-3,5-DBD), trans-1,3-diazabicyclo[4.4.0]decane (trans-1,3-DBD), cis-1,3-diazabicyclo[4.4.0]decane (cis-1,3-DBD), 1,5-diazabicyclo[3.3.1]nonane (DBN), trans-decahydro-8a,9a-diazaanthracene (trans-DDA), cis-decahydro-8a,9a-diazaanthracene (cis-DDA), 1,3-diazetidine (DAT), 1,3-imidazolidine (IMD), and 1,3-diazepane (DAP) have been studied by using density functional theory (DFT) and correlated ab initio methods. Possible conformers of these compounds were optimized at the B3LYP/6-31+G* level, and relative energies were evaluated at the MP2/6-311+G**//B3LYP/6-31+G* level. The experimental lithium ion affinities for reference molecules (i.e., ammonia and trimethylamine) are well-reproduced at these levels of theory. NBO analysis shows the influence of anomeric effects (n(N) → σ*(C-N) hyperconjugative interactions) on the conformational stability of the title compounds; however, the electrostatic and steric contributions included in the NBO Lewis term also affect the stabilities in some cases. The influence of anomeric effect is apparent in cis-DDA, where the nitrogen involved in n(N) → σ*(C-N) hyperconjugative interaction (cis-DDA-Li2) has a lithium ion affinity 1.7 kcal/mol lower than the nitrogen not involved in n(N) → σ*(C-N) hyperconjugative interaction (cis-DDA-Li1). In general, the computed lithium ion affinities were found to be conformationally dependent. The NBO results showed that the lithium ion affinities are also governed by the interplay of n(N) → σ*(C-N) hyperconjugative interactions and the steric strain caused upon lithiation. Further, the ring size also influences the lithium ion affinities in the 1,3-diaza monocyclic systems. In some complexes multiple coordination of the lithium ion is possible by inversion of one of the nitrogen atoms.

Preparation, structure and analysis of the bonding in the molecular entity (OSO)2Li{[AlF(ORF)3]Li[Al(ORF)4]} (RF = C(CF3)3)

The (SO(2))(2)Li[AlF(OR(F))(3)]Li[Al(OR(F))(4)] (1) (R(F) = C(CF(3))(3)) molecular entity was obtained by thermal decomposition of Li[Al(OR(F))(4)] followed by crystallization from liquid SO(2). 1, containing two SO(2) molecules eta(1)-O coordinated to Li(+), was structurally characterized by single crystal X-ray diffraction and NMR spectroscopy in SO(2)(l). Bonding analyses of 1 (bond valency units, AIM analysis, atomic charges, bond orders) show that 1 can be either considered as a Li(OSO)(2)(+) complex stabilized by the large WCA [AlF(OR(F))(3)](-)Li(+)[Al(OR(F))(4)](-) or as consisting of 2 SO(2), 2 Li(+), [AlF(OR(F))(3)](-), and [Al(OR(F))(4)](-) joined by electrostatic interactions into the discrete molecular entity 1. The bonding between Li(+) and SO(2) molecules is shown to be almost completely attributable to monopole-induced dipole electrostatic interactions. Theoretical gas phase lithium ion affinity of SO(2) is determined to be stronger than its silver(I) ion affinity owing largely to the shorter lithium SO(2) contacts in the calculated structures that increase the electrostatic interaction.

Characterizing Complexes with F−Li+−F Lithium Bonds: Structures, Binding Energies, and Spin−Spin Coupling Constants

Ab initio MP2/aug-cc-pVTZ calculations have been performed to determine the structures and binding energies of complexes with F-Li(+)-F bonds formed from the fluorine bases LiF, CH(3)F, HF, ClF, and FF. There is only a single minimum across the Li(+) transfer coordinate, and in each series, the lithiated homodimer is stabilized by a symmetric F...Li(+)...F bond. Complexes having LiF, CH(3)F, and HF as the base have similar structures, with linear F-Li(+)-F bonds and a head-to-tail alignment of the F-Li(+) bond dipole with the dipole moment vector of the base. In each series with a given acid, the binding energy decreases as the difference between the lithium ion affinities increases. EOM-CCSD coupling constants (1)J(F-Li), (1li)J(Li-F), and (2li)J(F-F) have also been evaluated. In complexes with essentially linear bonds, (2li)J(F-F) values are small and positive and increase quadratically as the F-F distance decreases. (1li)J(Li-F) and (1)J(F-Li) also vary systematically with distance. Comparisons are made between structural, energetic, and coupling constant properties of these complexes and corresponding complexes stabilized by F-H(+)-F hydrogen bonds.

An ab initio study of the structures and stabilities of the complexes of the bases N2O, CO2, and CO with the acids FH, H+, and Li+

The geometries of the complexes of the bases N2O, CO2, and CO with the acids FH, H+, and Li+ have been optimized at second-order Moller–Plesset perturbation theory with the 6–31+G(d, p) basis set. Interaction energies were computed at QCISD(T)/6–31+G(2d,2p). The complexes FH … ONN and FH … NNO have bent and linear geometries, respectively, in agreement with experimental data. The complex FH … OCO also has a bent equilibrium structure, although at room temperature a vibrationally averaged linear structure is observed. FH … CO and FH … OC have linear structures. N-and O-protonated N2O and protonated CO2 have bent structures, whereas C- and O-protonated CO are linear. The Li+ complexes of all of these bases are also linear. Association of H+, Li+, and FH with N2O occurs preferentially at O, although interaction energies for association at N are similar. In contrast, association of these acids with CO is significantly stronger at C than at O. The most stable hydrogen bonded complexes FH … ONN, FH … OCO, and FH … CO have similar stabilization enthalpies at 298 K of −2.2–2.5 kcal/mol. The order of proton affinities of these bases is CO > N2O > CO2, while the order of lithium ion affinities is reversed.

Ruthenium-based metallacrown complexes for the selective detection of lithium ions in water and in serum by fluorescence spectroscopy

Fluorescent dihydroxypyridine ligands were prepared by attaching pyrene-, dansyl-, and methoxycoumarin-fluorophores via dimethyleneamine linkers. The reaction of these ligands with [(p-cymene)RuCl(2)](2) or [(C(6)H(5)CH(2)NMe(2)H)RuCl(2)](2)Cl(2) resulted in the formation of 12-metallacrown-3 complexes, which possess strong affinity for lithium ions. By a judicious choice of the fluorophore and the arene pi-ligand, a macrocycle was obtained that could be used in aqueous solution to selectively and quantitatively detect lithium ions by fluorescence spectroscopy.

Novel weakly coordinating heterocyclic anions for use in lithium batteries

Ab initio calculations have been performed for a new family of lithium salts based on heterocyclic anions: [CF 3SON 4C 2 n ] − (0 ≤ n ≤ 4). In total, 10 different anions and their 1:1 ion pairs with lithium ions have been studied. The lithium ion affinity globally decreases with the degree of CN-substitution to the ring. Bidentate lithium ion coordination to the sulfonyl oxygen atom and one additional atom or to two adjacent ring nitrogen atoms is strongly preferred when structurally possible. The extremely low lithium ion affinities of the anions together with an appreciable stability towards oxidation make these salts possible candidates for future lithium battery electrolytes.

Rational design of electrolyte components by ab initio calculations

This paper is a small review of the use of computer simulations and especially the use of standard quantum-mechanical ab initio electronic structure calculations to rationally design and investigate different choices of chemicals/systems for lithium battery electrolytes. Covered systems and strategies to enhance the performance of electrolytes will range from assisting the interpretation of vibrational spectroscopy experiments over development of potentials for molecular dynamics simulations, to the design of new lithium salts and the lithium ion coordination in liquid, polymer, and gel polymer electrolytes. Examples of studied properties include the vibrational spectra of anions and ion pairs to characterize the nature and extent of the interactions present, the lithium ion affinities of anions, important for the salt solvation and the ability to provide a high concentration of charge carriers, the HOMO energies of the anions to estimate the stability versus oxidation, the anion volumes that correlate to the anion mobility, the lithium ion coordination and dynamics to reveal the limiting steps of lithium ion transport, etc.

Ab initio studies of complexation of anions to neutral species

The complexation of simple anions (F − and Cl −) to different neutral species, anion-coordinating agents, has been studied using electronic structure calculations. The obtained changes in the equilibrium constants for salt dissolution reactions in different typical electrolyte systems are reported. In addition the lithium ion affinities of the obtained anionic complexes have been calculated. Using the present results we discuss strategies for future usage of anion complexing agents and make recommendations of salt and agent combinations for better lithium battery electrolyte performance.

Electrochemical Stability and Lithium Ion-Anion Interactions of Orthoborate Anions (BOB, MOB, BMB), and Presentation of a Novel Anion: Tris-oxalato-phosphate

Ab initio calculations reveal the extraordinary low lithium ion affinities of the orthoborate anions bis(oxalate)borate (BOB), malonato-oxalatoborate (MOB), and bis(malonato)borate (BMB). HF and MP2 calculations reveal these anions to be less prone to associate with Li + (by ∼10%) than most anions used today, e.g., PF 6 - , BF 4 - , and TFSI, in low dielectric media such as polymeric electrolytes. Furthermore, by using self-consistent reaction field calculations to model the effect of high dielectric solvents present, the applicability of these anions also for liquid and gel electrolytes was proven. Future directions of lithium salt synthesis are outlined and exemplified by a new anion, suggested here for the first time. The HOMO levels of the anions are correlated to electrochemical stabilities in electrolytic solutions; all studied anions can be anticipated to have wide stability ranges. Finally, a new methodology to obtain starting data for geometry optimizations of cation-anion pairs by global optimization is presented. © 2005 The Electrochemical Society. All rights reserved.

Novel Hückel stabilised azole ring-based lithium salts studied by ab initio Gaussian-3 theory

Gaussian-3 theory calculations have been performed for a new family of lithium salts with heterocyclic anions–Li+[N5C2n]− (0 ≤ n ≤ 5). Eight different anions and the most stable 1∶1 lithium ion pairs have been studied for each anion. The lithium ion affinity of the anions decreases with the gradual CN-substitution and is thus lowest for the [N5C10]− anion. The stability vs. oxidation, inferred from the HOMO values, is large for all anions. In addition, the volume and aromaticity of the anions have been evaluated.

Anion cryptands: a way to increased cation transport in polymer electrolytes

The complexation of different simple anions (F −, Cl −, BF 4 − and ClO 4 −) with a neutral cryptand, with neutral BN dipoles as functional units, and modifications thereof has been studied using ab initio Hartree–Fock calculations. F − is the most strongly preferred anion for all cryptand versions, except for the largest cavity cryptand for which Cl − is preferred. The formed complexes in general show very low lithium ion affinities, much lower than those for anions such as PF 6 − and TFSI (by up to 50%). The lowest lithium affinity is obtained for the combination of the smallest cryptand and the F − anion. Implications of using these cryptands in polymer electrolytes are discussed.

Constraining of small-ring cyclic ether triads by stereodefined spiroannulation to an inositol orthoformate platform. Solution- and gas-phase alkali metal binding affinities for three- to five-membered ring structural combinations.

The structural features most conducive to complexation of the alkali metal ions Li(+), Na(+), and K(+) in a series of constrained inositol orthoformate derivatives have been probed in solution, in the solid state, and in the gas phase by electrospray ionization mass spectrometry. The eight spirotricyclic polyethers differ in the size of the rings containing the potentially ligating oxygen atoms. Although the ring sizes have been limited to three to five atoms inclusively, the combinations of oxirane, oxetane, and tetrahydrofuran are rather extensive and consist of many options. The overall trend for lithium ion affinity is [5.5.5] > [ 5.5.4] > [4.4.4] > [5.5.3] > [5.4.3] > [4.4.3] > [1.1.1] > [3.3.1], an ordering that correlates with the differing polarizabilities of the oxygen atoms, ease of alignment of the nonbonded electron pairs, and the overall size of the ligand as gauged by nonbonded O......O distances.

Propargylic Sulfone-Armed Lariat Crown Ethers: Alkali Metal Ion-Regulated DNA Cleavage Agents

Alkali metal ion concentrations within cells are regulated during the cell cycle and may be significantly altered in cancer cells versus normal cells. Thus, the selective destruction of cancer cells might be achieved by agents that marry alkali metal ion recognition elements, such as crown ethers, with DNA-cleaving moieties. We have prepared a series of propargylic sulfone-armed lariat crown ethers, which bind sodium and potassium ions and exhibit little affinity for lithium ions, as determined by a picrate extraction assay. We have investigated the supercoiled DNA cleavage efficiency of these lariat crown ethers in the presence of various alkali metal ions. Monomeric propargylic sulfone-armed crown ethers 9b and 10b cleave DNA at physiologically relevant pH and exhibit modest increases in DNA cleavage efficiency in the presence of potassium and sodium as compared to lithium. In Tris-containing buffer, the monomeric lariat crown ether 10b cleaves DNA in a sodium ion-dependent fashion, producing 66% more DNA cleavage in the presence of 5.7 mM sodium than in the absence of added sodium. The dimeric propargylic sulfone-armed lariat crown ether 11 cleaves DNA over 10-fold better in the presence of potassium than in the presence of lithium. While the level of metal ion discrimination exhibited by these compounds is rather modest, they do represent the first successful attempt to marry molecular recognition of specific alkali metal ion with covalent modification of DNA.

A possible origin of [M − nH + mX] ( m− n)+ ions (X = alkali metal ions) in electrospray mass spectrometry of peptides

The [M − nH + mX] ( m− n)+ (X = alkali metal ion) are common ions in the mass spectrum of a peptide that is electrosprayed in the presence of an alkali metal salt or hydroxide. The feasibility of forming [M − nH + mX] ( m− n)+ ions in the gas phase including those in the lens region of the mass spectrometer via ion–molecule reactions and/or reactions between components of collisionally activated adducts was investigated. The Li + ion was selected for examination since its salts are computationally the least expensive among alkali metal salts. The lithium ion affinities of the [M − H] − ions of N-methylacetamide, acetic acid, and 1-propanamine were calculated by means of density functional theory (DFT) at various levels of theory, including B3LYP/6-311++G( d, p). These three compounds were selected as representatives of relevant functional groups on a peptide. The calculated lithium ion affinities, together with evaluated thermochemical data, were used to calculate the enthalpies of reactions between the model compounds and LiOH, LiCl, and Li(H 2O) + that might lead to the formation of [M − nH + mX] ( m− n)+ . A number of these reactions were found to be exothermic or slightly endothermic (Δ H° < +20 kcal/mol). DFT calculations on the energetics of a model reaction revealed a relatively flat potential energy hypersurface containing a well of approximately 35 kcal/mol in depth and devoid of significant barriers. These results are used to postulate the formation of [M − nH + mX] ( m− n)+ ions in the gas phase in the ion source and/or in the lens region via collisions between an ionic peptide and neutral lithium compounds or collisional activation of lithium–peptide adducts.

The order of lithium ion affinities for the 20 common α-amino acids. Calculation of energy-well depth of ion-bound dimers

In an earlier publication it was shown that the kinetic method for determination of proton affinities can be satisfactorily explained when the critical energies for decomposition of the proton-bound dimers are calculated from the Marcus equation. In this work it is shown that the critical energies for decomposition of alkali metal ion-bound dimers also seem to follow the Marcus equation. This supports the application of the kinetic method for measurements of alkali metal-ion affinities of organic molecules. Based on unimolecular decompositions of Li+-bound dimers, the order of lithium ion affinity of the common α-amino acids has been established as: Arg > His > Gln > As n > Lys > Trp > Glu > Asp > Tyr > Met > Phe > Thr > Pro > Ser > Ile > Leu > Val > Cys > Ala > Gly.

Basis Set and Correlation Effects on Computed Lithium Ion Affinities

Ab initio calculations have been performed to investigate the basis set and correlation energy dependence of computed lithium ion affinities of a series of first- and second-row neutral bases (NH3, H2O, HF, HCN, CO, PH3, H2S, HCl) and of the corresponding anions which result from the loss of H+. The basis set dependence was evaluated at fourth-order many-body Moller−Plesset perturbation theory [MBPT(4) = MP4], using the Dunning correlation-consistent polarized split-valence basis sets (cc-pVXZ, where X = D for double, T for triple, and Q for quadruple split) and these sets augmented with diffuse functions on atoms other than H and Li (aug‘-cc-pVXZ). The presence of diffuse functions in the basis set lowers computed Li+ affinities and reduces the basis set superposition error. Computed aug‘-cc-pVXZ Li+ affinities converge with increasing basis set size, with satisfactory convergence occurring at aug‘-cc-pVTZ. Comparison with CCSD(T) results indicates that the Moller−Plesset expansion appears to be convergi...