Lithium Cations Research Articles

Enhanced lithium ionic conductivity of lithium perchlorate in the metal-organic framework matrix

Nanocomposite solid electrolytes were prepared by impregnation of LiClO4 into pores of the metal-organic framework Cr3[C6H4(COO)2]3F (MIL-101(Cr)), and their conductivity was investigated. At temperatures 25–150 °C and relative humidity of 50%, the composites easily absorb water with formation liquid phase in the pores and have conductivity values typical for water solutions. Conductivity decreases with diminishing the humidity; however, complete dehydration may be achieved only after prolonged heating in vacuum at 180 °C. The concentration dependence of conductivity of dehydrated samples goes through the maximum at nearly 6 mol% of MIL-101(Cr) and reaches 3 × 10−3 S/cm at 160 °C; the activation energy decreases in the nanocomposites. Using the volt-amperometric technique on the sample with two nickel electrodes, the electrochemical decomposition voltage value was found to be nearly 3.5 V at 160 °C. It suggests that the ionic conductivity is caused by lithium cations rather than protons or electrons.

Negative Capacitance and Inverted Hysteresis: Matching Features in Perovskite Solar Cells.

Negative capacitance in the low-frequency domain and inverted hysteresis are familiar features in perovskite solar cells, which origin is still under discussion. Here we use impedance spectroscopy to analyze these responses in methylammonium lead bromide cells treated with lithium cations at the electron-selective layer/perovskite interface and in iodide devices exposed to different relative humidity conditions. Employing the surface polarization model, we obtain a time constant associated with the kinetics of the interaction of ions/vacancies with the surface, τkin, in the range of 100-102 s for all the cases exhibiting both features. These interactions lead to a decrease in the overall recombination resistance, modifying the low-frequency perovskite response and yielding a flattening of the cyclic voltammetry. As a consequence of these results we find that negative capacitance and inverted hysteresis lead to a decrease in the fill factor and photovoltage values.

Experimental and Computational Study of the 1,5-O → N Carbamoyl Snieckus-Fries-Type Rearrangement.

The reactions of o-lithiated O-aryl N,N-diethylcarbamates with different C-N multiple bond electrophiles have been thoroughly studied. A 1,5-O → N carbamoyl shift, a new variation of the anionic Fries-type rearrangement, takes place when nitriles, imines, or alkylcarbodiimides are employed. In these cases, the carbamoyl group plays a dual role as a directing group, building up a variety of functional groups through the 1,5-O → N carbamoyl migration. On the other hand, the use of iso(thio)cyanates and arylcarbodiimides led to non-rearranged o-functionalized O-arylcarbamates. This reactivity was further computationally explored, and the governing factor could be traced back to the relative basicity of the alternative products (migrated vs nonmigrated substrates). This exploration also provided interesting insights about the degree of complexation of the lithium cations onto these substrates. A new access to useful 2-hydroxybenzophenone derivatives has also been developed.

Lithium Cation-Catalyzed Benzene Diels-Alder Reaction: Insights on the Molecular Mechanism Within the Molecular Electron Density Theory.

The lithium cation Li+-catalyzed Diels-Alder (DA) reactions of benzene toward a series of acetylenes of improved nucleophilicity can be described within the context of the molecular electron density theory (MEDT) at the ωB97XD/6-311G(d,p) level. Conceptual density functional theory indices characterize the crown ether solvated complex benzene-lithium Bz-Li-Cro as a superelectrophile. Coordination of a lithium cation to benzene does not change substantially the electron localization function electronic structure of benzene. The DA reaction of Bz-Li-Cro with acetylene shows a reduction of the energy of activation of 6.9 kcal·mol-1, which is not sufficient for the reaction to take place, thus demanding the participation of strong nucleophilic acetylenes. DA reactions of complexes Bz-M-Cro (M = Li, Na, and K) are decelerated with the decrease of the ionization potential of the alkali metal. The one-step mechanism of these lithium cation Li+-catalyzed DA reactions changes to a two-step one for the reaction with dimethyl propynamine. The present MEDT study proves that analysis of the electrophilicity and nucleophilicity indices is an excellent tool for experimental organic chemists to understand, even to predict, the chemical organic reactivity.

Impact of ionic liquid on lithium ion battery with a solid poly(ionic liquid) pentablock terpolymer as electrolyte and separator

In this study, the physical, transport, mechanical, morphological, and electrochemical properties of a ternary blend solid polymer electrolyte (SPE) (poly(ionic liquid) (PIL) multiblock polymer, lithium salt, and ionic liquid (IL)) were systematically investigated as a function of IL concentration. With increasing IL concentration, the conductive volume increases along with the polymer chain segmental mobility. This facilitates high ionic conductivity, while the mechanical modulus exhibits a percolation threshold. Surprisingly, at higher IL concentrations, there is a reduction in the lithium cation mobility as evidenced by pulsed-field gradient nuclear magnetic resonance, which coincides with an increased overpotential evidenced by lithium metal stripping and plating. Stable lithium ion battery cycling durability (over 100 cycles at room temperature) is demonstrated with the ternary blend SPE as the electrolyte and separator. This work provides valuable insights into the design of new SPEs with both high ionic conductivity and improved battery stability.

Lithium cation conductivity of solid solutions in Li6-2xMxZr2O7 (M = Mg, Ca, Zn) systems

Glycine-nitrate method is used to synthesize samples in Li6-2xMxZr2O7 (M = Mg, Ca, Zn) systems. Boundaries of single-phase regions of solid solutions based on monoclinic Li6Zr2O7 are roughly determined, temperature dependencies across the range of 300–600°С and concentration dependencies of their conductivity are studied. The maximum lithium cation conductivity of the synthesized solid solutions exceeds the conductivity of undoped Li6Zr2O7 by more than two orders of magnitude. The obtained results are compared with the available literature data on the transport properties of Li6Zr2O7 and solid solutions based on it. The influence of electronegativity of M dopants on the transport properties of the investigated solid electrolytes is studied.

Metal-Ligand Cooperativity of the Calix[4]pyrrolato Aluminate: Triggerable C-C Bond Formation and Rate Control in Catalysis.

Metal‐ligand cooperativity (MLC) had a remarkable impact on transition metal chemistry and catalysis. By use of the calix[4]pyrrolato aluminate, [1]−, which features a square‐planar AlIII, we transfer this concept into the p‐block and fully elucidate its mechanisms by experiment and theory. Complementary to transition metal‐based MLC (aromatization upon substrate binding), substrate binding in [1]− occurs by dearomatization of the ligand. The aluminate trapps carbonyls by the formation of C−C and Al−O bonds, but the products maintain full reversibility and outstanding dynamic exchange rates. Remarkably, the C−C bonds can be formed or cleaved by the addition or removal of lithium cations, permitting unprecedented control over the system's constitutional state. Moreover, the metal‐ligand cooperative substrate interaction allows to twist the kinetics of catalytic hydroboration reactions in a unique sense. Ultimately, this work describes the evolution of an anti‐van't Hoff/Le Bel species from their being as a structural curiosity to their application as a reagent and catalyst.

Metal–Ligand Cooperativity of the Calix[4]pyrrolato Aluminate: Triggerable C−C Bond Formation and Rate Control in Catalysis

AbstractMetal‐ligand cooperativity (MLC) had a remarkable impact on transition metal chemistry and catalysis. By use of the calix[4]pyrrolato aluminate, [1]−, which features a square‐planar AlIII, we transfer this concept into the p‐block and fully elucidate its mechanisms by experiment and theory. Complementary to transition metal‐based MLC (aromatization upon substrate binding), substrate binding in [1]− occurs by dearomatization of the ligand. The aluminate trapps carbonyls by the formation of C−C and Al−O bonds, but the products maintain full reversibility and outstanding dynamic exchange rates. Remarkably, the C−C bonds can be formed or cleaved by the addition or removal of lithium cations, permitting unprecedented control over the system's constitutional state. Moreover, the metal‐ligand cooperative substrate interaction allows to twist the kinetics of catalytic hydroboration reactions in a unique sense. Ultimately, this work describes the evolution of an anti‐van't Hoff/Le Bel species from their being as a structural curiosity to their application as a reagent and catalyst.

Lithium cation basicity estimates of lignin β-O-4 dimers by the kinetic method utilizing a novel ladder approach

Lithium cation basicity estimates of lignin β-O-4 dimers by the kinetic method utilizing a novel ladder approach

Helicates with Ether‐Substituted Catechol Esters as Ligands

Mono‐ or biscatechol esters with ether‐type substituents or spacers form either triple lithium bridged dimeric helicates or triple stranded helicates with the ability to bind three lithium cations in their interior. Hierarchical helicates with ether or thioether substituents show in solution a monomer‐dimer equilibrium which is independent of the heteroatom in the ester substituent. However, dimerization constants are significantly lower than for corresponding alkyl derivatives. Dinuclear helicates with oligoether spacers are well obtained in the presence of lithium cations. Upon removal of the cations the helicates expand and successive addition of LiCl results in compression again.

Reversible dimerization of anion radicals of carbonyl compounds and the electrosynthesis of pinacols. The case of 9-fluorenone

Reversible dimerization of the anion radicals of carbonyl compounds was studied by cyclic voltammetry, chronoamperometry, electrolysis, digital simulation and quantum chemical calculations using electroreduction of 9-fluorenone in DMF/0.1 M Bu4NClO4 as an example. The experimental data confirmed that this reaction is thermodynamically unfavorable as it was predicted by DFT calculations. In contrast with some other anion radicals, neither ion pairing of 9-fluorenone anion radicals with lithium cation nor their hydrogen bonding with water shifts the dimerization equilibrium to the dimeric product. Reversibility of the dimerization decreases in the presence of phenol due to the protonation of the dimeric dianion and to the irreversibility of dimerization of the anion radical – phenol complexes. The contribution of these two pathways to general hydrodimerization process is discussed.

Revisiting the energy efficiency and (potential) full-cell performance of lithium-ion batteries employing conversion/alloying-type negative electrodes

The energy efficiency of new lithium-ion chemistries is a very important, but frequently not provided performance measure for new alternative active materials for application as negative and positive lithium-ion battery (LIB) electrodes. This is particularly true for those active materials, not hosting lithium cations via insertion mechanisms, but via alloying and/or conversion reactions.Herein, the energy efficiency of alternative negative electrode active materials hosting lithium via combined conversion and alloying processes and the impact factors on the energy efficiency of such compounds in complete battery cells (full-cells) is revisited. Specifically, the effect of (i) varying the relative contribution of the conversion and alloying reaction, (ii) limiting the specific capacity, (iii) pre-cycling and pre-lithiating the anode, as well as (iv) the choice of the active material for the positive electrode, is investigated. The results show that a proper combination of these measures may enable lithium-ion cells based on conversion/alloying anodes that provide energy efficiencies of >95%, accompanied by gravimetric energy densities that might outperform graphite-based lithium-ion cells.

Heavy metal contamination and exposure risk assessment via drinking groundwater in Vehari, Pakistan.

The presence of toxic substances in aquifers, particularly potentially toxic heavy metals, is an important environmental and social concern worldwide. These heavy metals are capable to exert many injurious health effects in human beings by intake of drinking metal-contaminated water. However, very little attention is paid towards quantitative and qualitative analysis of groundwater used for drinking purpose in several less-developed countries. Therefore, this study was intended to estimate, for the first time, the heavy metal levels in groundwater/drinking water in District Vehari, Pakistan. A total of 129 groundwater samples were obtained and subjected to analyze heavy metal concentrations (lead, copper, cadmium, nickel, manganese, chromium, iron, and zinc). Moreover, pH, electrical conductivity, temperature, total dissolved solids, and anion (carbonates, chloride, and bicarbonates) and cation (calcium, potassium, sodium, lithium, and barium) contents of groundwater were also determined. It was noticed that the values of several groundwater physicochemical characteristics such as cation contents, alkalinity, chloride concentration, and especially the concentrations of heavy metals such as Pb (93%), Cd (68%), and Fe (100%) were higher than their limit values given by WHO. Principal component analysis separately grouped heavy metals and physicochemical characteristics of groundwater. The risk assessment indices predicted potential carcinogenic risks due to the consumption of metal-rich groundwater, predominantly with Cd (0.0007-0.03). The mean hazard quotient (HQ) values for all the metals were < 1, while Pb showed HQ > 1 envisaging non-carcinogenic risk with the consumption of studied groundwater. The findings of the study emphasized on the need of appropriate approaches to remediate groundwater before being used for drinking purpose.

Influences of Steric Factors on the Reactivity and Structure of Diorganoalkoxysilylamides

The combination of an alkoxy and an amino function combined in one silane is rarely found due to the difficult synthesis and isolation.[1] However, this combination offers unique opportunities to investigate the influence of steric requirements or the size of a metal on the structure or reactivity of alkoxysilylamides towards electrophiles by varying the metallating reagent (n‐butyllithium or di‐n‐butylmagnesium) or the organo group on the amino function. For this purpose, we synthesized two alkoxyaminosilanes with acidic NH units that can be metalated. On the one hand, the tert‐butylamino‐substituted (tert‐butylamino)‐methoxydiphenylsilane (1) and on the other hand the isopropylamino‐substituted methoxydiphenyl(isopropylamino)silane (2). The resulting structures showed an interesting interrelation between the Si–O or Si–N bond lengths and the strength of the coordinative bond to the corresponding metal cation (lithium or magnesium).

Dehydrogenation of 2,3-Butanediol to 3-Hydroxybutanone Over CuZnAl Catalysts: Effect of Lithium Cation as Promoter

The dehydrogenation of 2,3-butanediol (BDO) to 3-hydroxybutanone (HBO) was studies over Li cation-doped CuZnAl catalysts. The catalyst samples were characterized by XRD, XPS, H2-TPR and SEM techniques. The characterization results showing that doping with Li cation obviously modified the surface morphology of CuZnAl catalysts; decreased the reduction temperature of CuZnAl catalysts; and finally increased the amount of Cu active sites. The reaction results showing that, Li modified CuZnAl catalysts obviously enhanced the selectivity of the dehydrogenation of BDO to HBO by inhibiting the dehydration of BDO. The Li(2%)–Cu(44%)–Zn(38%)–Al(16%) exhibited the highest activity for dehydrogenation of BDO, with the conversion rate of BDO is 72.4% and the selectivity of HBO is 95.9% at 260 °C. This catalyst shows excellent stability for more than 100 h without significant deactivation.

Impact of the Lithium Cation on the Voltammetry and Spectroscopy of [XVM11O40]n- (X = P, As (n = 4), S (n = 3); M = Mo, W): Influence of Charge and Addenda and Hetero Atoms.

Polyoxometalates (POMs) have been proposed as electromaterials for lithium-based batteries because they provide access to multiple electron transfer reactions coupled to fast lithium ion transport processes and high stability over many redox cycles. Consequently, knowledge of reversible potentials and Li+ cation-POM anion interactions provides a strategic basis for their further development. In this study, detailed cyclic voltammetric studies of a series of [XVVM11O40]n- (XVM11n-) POMs (where X (heteroatom) = P (n = 4), As (n = 4), and S (n = 3) and M (addenda atom) = Mo, W) have been undertaken in CH3CN in the presence of LiClO4, with n-Bu4NPF6 also present when required to keep the ionic strength close to constant value of 0.1 M. An analysis of the data has allowed the impact of the POM charge, and addenda and hetero atoms on the reversible potentials and the interaction between Li+ and the oxidized XVVM11n- and reduced XVIVM11(n+1)- forms of the VV/IV redox couple to be determined. The SVV/IVM113-/4- process is independent of the Li+ concentration, implying the absence of the association of this cation with either SVVM113- or SVIVM114- redox levels. However, lithium-ion association constants for both VV and VIV redox levels were obtained from a comparison of simulated and experimental cyclic voltammograms for the reduction of the more negatively charged XVVM114- (X = P, As; M = Mo, W), since the Li+ interaction with these more negatively charged POMs is much stronger. The interaction between Li+ and the oxidized, XVVM11n-, and reduced, XVIVM11(n+1)-, forms was also investigated by 51V NMR and EPR spectroscopy, respectively, and it was confirmed that, due to their lower charge density, SVVM113- and SVIVM114- interact significantly less strongly with the lithium ion than XVVM114- and XVIVM115- (X = P, As). The lithium-POM association constants are substantially smaller than the corresponding proton association constants reported previously, which is attributed to a smaller surface charge density. The much stronger impact of Li+ on the WVI/V- and MoVI/V-based reductions that occur at more negative potentials than the VV/IV process also has been qualitatively evaluated.

Impact of Lithium and Potassium Cations on the Mössbauer Spectral and Electrical Properties of Two Mixed-Valence Iron(II/III) Phosphites

Based on the combined corrected chemical analysis, the single-crystal X-ray structural results, and the revised Mössbauer spectral analysis, the best formulation of Li1.4(1)[Fe4.4(1)IIFe0.6(1)III(HPO3)6]·1.47(3) H2O, 1b, has been obtained; also, from a revised Mössbauer spectral analysis, a revised formulation of K0.95(5)[Fe3.95(5)IIFe1.05(5)III(HPO3)6]·0.5 H2O, 2m, has been obtained. The revised analysis of the room-temperature Mössbauer spectral parameters for both compounds is consistent with their crystallographic structures and the different nature and occupancies of the Li+ and K+ crystallographic sites. From a detailed analysis of the impedance spectroscopy measurements of Li1.43[Fe4.43IIFe0.57III(HPO3)6]·1.5 H2O, 1, between 123 and 189 °C, two processes involving the electric charge response to the ac electric field have been identified. An activation energy for the charge transfer in 1 of 0.91(2) eV or 7340(160) cm–1 has been obtained; the charge transfer may involve a correlated hopping of the Li+ ion and an electron between the iron(II) and iron(III) ions.

Electrochemical Performance of (MgCoNiZn)1-xLixO High-Entropy Oxides in Lithium-Ion Batteries.

High-entropy oxides (HEOs), which are a new class of single-phase solid solution materials, have recently attracted significant attention as an anode material for lithium-ion batteries (LIBs). In this study, (MgCoNiZn)1-xLixO (x = 0.05, 0.15, 0.25, and 0.35) HEOs were synthesized and their electrochemical performances as the anode material were observed in LIBs. X-ray photoelectron spectroscopy (XPS) analysis showed that the increase in the lithium cation concentration causes generation of more oxygen vacancies, which greatly affected the electrochemical performance of (MgCoNiZn)1-xLixO HEO anodes, in the structure. The more the oxygen vacancy concentration in the anode, the higher the discharge capacity in the LIB. The (MgCoNiZn)0.65Li0.35O anode had 1930 mA h g-1 initial and 610 mA h g-1 stable (after 130 cycles) discharge capacities at a current density of 1000 mA g-1. This work clearly indicated that designing a HEO with abundant oxygen vacancies in the structure was a very efficient strategy to improve the electrochemical performance of the HEO electrode for LIBs.

Pre-Doping Strategies of Graphite Negative Electrode in Lithium-Ion Capacitors

Lithium-ion capacitors (LICs) are intermediate devices between lithium-ion batteries (LIBs) and electrical double-layer capacitors (EDLCs).1,2,3 Their design consists of an activated carbon positive electrode that stores charges by capacitive behavior, while lithium cations are inserted in the graphite negative electrode. Thanks to their high cell voltage as well as the capacity of their electrodes, they can address quite a wide range of applications. Indeed, their energy density approaches that of lead-acid batteries, and their power density is close to that of EDLCs. However, the interest in such hybrid design is mitigated by the need of an initial prelithiation step of the graphite anode which is mandatory to further operate the LIC device. This step is usually performed using a sacrificial metallic lithium foil.3 More recently, alternative strategies have been proposed such as taking advantage of specific charging profiles on the first cycle that provide lithium cations from the electrolyte4, or using lithiated compounds that serve on the first charging cycle as the lithium cations source5,6. All these strategies introduce in the device many drawbacks including potential hazards, difficult manufacturing process, or/and high CO2 footprint. In this communication, we will present strategies that take advantage of low CO2 footprint material. Lithiated organic molecules have been recently envisioned as electrode materials for all-organic Li-ion batteries.7 Some of these molecules do not show any cycling ability and only provide lithium cations in an irreversible manner during the first charge. This drawback can be turned into an advantage in LICs where sacrificial compounds used for the prelithiation must be the lithium cations source but only during the first charge. During the subsequent cycles, the delithiated compounds must remain electrochemically inactive. Subsequently, our strategy consists in the use of a lithiated organic material, namely 3,4–dihydroxybenzonitrile dilithium salt (Li2DHBN) that is mixed with activated carbon at the positive electrode of the LIC, and which can irreversibly provide lithium cations to the graphite electrode during an initial in-situ charging step without any negative effects with respect to further operation of the LIC.8 It paves the way toward simpler and safer LICs that are easily recyclable.

Modeling the Effect of Dimethylsulfoxide on the Energy of Interaction of Ions in Nafion-Like Membranes

Quantum chemical modeling is performed for the distancing of lithium and ammonium cations from the –O–CF2–CF2–SO$$_{3}^{ - }$$ functional group typical of Nafion-like polymer membranes in the presence of a different number of dimethylsulfoxide molecules. The cluster approach plus the B3LYP density functional and 6-31G* basis are used. It is found that cations are quite strongly bound to anions in the considered systems if the number of plasticizer molecules in them is low (n ≤ 4). Solvent molecules not incorporated in the first coordination sphere can act as polarizable dielectric layers between cations and anions upon an increase in the value of n. This allows the distance between a cation and an anion to be increased to 7–14 A with a moderate consumption of energy (∼0.3 eV).