Lithium Cations Research Articles

Investigation on the local structure and properties of molten Li2CO3-K2CO3 binary salts by machine learning potentials

In recent years, (LinK1-n)2CO3 binary melts have been investigated as the promising electrolyte matrixes of the fuel cell. Many researchers moved to the investigation of local structure and properties of the melts. In this paper, machine learning interatomic potentials were developed based on first-principle datasets in order to research the local structure and properties of molten (LinK1-n)2CO3 (n = 0.4,0.5,0.6) binary salts. The trained machine learning potentials, which enable similar accuracy relative to DFT and high efficiency, can yield precise descriptions of microstructure and macro properties of Li2CO3-K2CO3 binary melts. The information of the microstructure evolution was analyzed through partial radial distribution functions, coordination numbers and bond angle distribution functions. It is observed that lithium cation exhibits more stable coordination and destroys the C-O ion pairs. Further, comparing the inter-ionic partial radius distribution function diagrams of binary melts and those of pure Li2CO3 and K2CO3 melts, the changing regularities of interatomic strength and arrangement were obtained. Macro properties including density, self-diffusion coefficients, thermal conductivity and viscosity at target temperature range were calculated by the potentials and MD simulations. The temperature effect and concentration effect in properties were explored. This work exhibits a thorough understanding of the local structure and properties of Li2CO3-K2CO3 melts and reveals the accuracy of machine learning potentials on lithium-potassium melts for the first time.

Cover Feature: Fine‐Tuning the Thermal Relaxation Dynamics of Indigo‐Based Photoswitches Using Selective Non‐Covalent Interactions Without Chemical Modification (ChemPhotoChem 4/2022)

The Cover Feature shows a molecular complex formed between the Z-isomer of an indigo-based photoswitch and a lithium cation. The formation of this complex stabilizes the Z-isomer and slows the thermal relaxation rate of this photoswitch. In contrast, the uncomplexed molecules have a faster relaxation rate, as shown by the motion blur. Cover image designed by Julie Liu (SIAIS, ShanghaiTech University). More information can be found in the Research Article by Bo Qiao and co-workers.

Harnessing Heteropolar Lithium Polysulfides by Amphoteric Polymer Binder for Facile Manufacturing of Practical Li-S Batteries.

Enabling efficient and durable charge storage under high sulfur loading and lean electrolyte remains a paramount challenge for Li-S battery technology to truly demonstrate its commercial viability. This work reports an amphoteric polymer binder, whose negatively and positively charged moieties allow for coregulation of both lithium cations and heteropolar lithium polysulfides through multiple intermolecular interactions. These interactions and the physical properties lead to simultaneously improved Li+ transport, polysulfide adsorption and catalysis, cathode robustness and anode stability. Therefore, this multifunctional binder endows Li-S batteries with compelling overall performances even under rigorous conditions. At low sulfur loading and copious electrolyte, the cell shows a low capacity-fading rate of 0.056% cycle-1 upon 700 cycles. At sulfur loading of 6.8 mg cm-2 and low E/S of 6 µL mg-1 , the cell still delivers stable areal capacities between 4.2 and 4.8 mAh cm-2 in 50 cycles without obvious decay at 0.2 C. The commercial feasibility of this work is further manifested by its zero added weight, low material cost, and ease of manufacturing and scale-up. The efficacy and simplicity of this work symbolize an example of lab-scale battery research aiming at improved technology and manufacturing readiness level.

Shielding the electrostatic attraction by design of zwitterionic single ion conducting polymer electrolyte with high dielectric constant

According to Coulomb's law, besides the design of bulky anion, increase in dielectric constant can also reduce the electrostatic attraction force, both of which are benefit for ion dissociation. Here, we report a zwitterionic single ion conducting polymer electrolyte by chemically grafting two propanesulfonyl(trifluoromethanesulfonyl)imide groups to the nitrogen of poly(biphenyl piperidium) (PBP-g-Li(PSI)2). One of side-chain groups burdens negative charge to counterbalance the positive charge of quaternary ammonium of main chain, and the other one provides lithium ion to conduct charge. Poly(biphenyl piperidinium) grafted with one lithium propanesulfonyl(trifluoromethanesulfonyl)imide (PBP-g-LiPSI) is synthesized for contrast. It is discovered that the dielectric constant of PBP-g-Li(PSI)2 is 22.3 at 2 MHz which is 3.5 times that of PBP-g-LiPSI, and the ionic conductivity of PBP-g-Li(PSI)2 gel polymer electrolyte membrane is 2.41 × 10−4 S cm−1 at 25 °C, nearly twice that of PBP-g-LiPSI gel polymer electrolyte membrane. The dipole structure of bonded bis(sulfonyl)imide anion and quaternary ammonium cation can shield the electrostatic attraction between lithium cation and immobilized anion as confirmed by Li 1s XPS and 7Li NMR. Zwitterionic polymer electrolyte not only withstands galvanostatic cycling in lithium symmetric cell at ±0.5 mA cm−2@2 mAh cm−2 for 2000 h, but also performs stably in lithium metal secondary battery.

Amphiphilic α-cyanostilbene mesogens with oligooxyethylene polar tails: syntheses and properties

ABSTRACT A series of amphiphilic rodlike α-cyanostilbene mesogens bearing an α-cyanostilbene core, with one/three lipophilic and flexible alkyl chains at one end and a polar oligooxyethylene (EO) at the opposite end, have been synthesized and investigated by polarized optical microscopy (POM), differential scanning calorimetry (DSC), X-ray scattering, scanning electron microscope (SEM), UV-vis spectroscopy and photoluminescence as well as CV measurements. These compounds can self-assemble into photoresponsive liquid crystalline phases and possess AIEE characteristics, mechanofluorochromic properties and Fe3+ recognition properties. The conductivity of the lithium cation complex was also measured to be 2.6 × 10−7 S m−1. Such compounds can be considered as a kind of multifunctional materials.

Molecular dynamics of the interfacial solution structure of alkali-halide electrolytes at graphene electrodes

The interactions of graphene electrodes with aqueous solutions of electrolytes play important roles in many technologies such as capacitive deionisation. Particularly important is the surface adsorption of ions due to the electric potential of the electrode. In this paper, we have studied structural changes in several prototypical aqueous solutions of electrolytes (NaCl, KCl, and LiCl) in contact with graphene induced by its either positive or negative electric charge, under ambient conditions. We have carried out molecular-dynamics simulations using the most accurate interaction models available. We have analysed the solution structure using an advanced analysis of the intermolecular bonding, and also standard properties such as density and charge density profiles, electrostatic potential, and screening functions. Our results show that the graphene charge has nearly no translational effect on water molecules, whereas it significantly changes their orientations, and the effect on ions’ distributions differ from solution to solution. Larger ions, whose hydration shells are weaker, are affected directly in an intuitive fashion, i.e., cations are attracted by negatively charged graphene and vice versa, whereas effects on smaller ions may vary and may be even counterintuitive, e.g., the number of chlorine anions in aqueous KCl in contact with negatively charged graphene is greater when compared to neutral graphene. The surplus of chlorine anions adsorbed on a positively charged electrode strengthens the structure of water and counterintuitively rotates the water molecules in the second layer pointing their electric dipoles preferentially to the electrode. The surplus of cations due to a negatively charged electrode is accompanied by a weakening of the water structure in the case of larger ions, whereas in the case of the lithium cation the structure is stronger due to the direct effects of the graphene charge on water molecules. Regardless of the graphene charge, the total number of intermolecular bonds connected with a single water molecule is nearly independent of the distance from the graphene surface and the same applies to the number of intermolecular bonds connected with a single ion, which means that whenever a particle loses an intermolecular bond it nearly always forms a new bond as a compensation.

Topological analysis of possible conductivity pathways in LiRW2O8 (R = M3+ - lanthanides and d-metals)

This paper presents the results of a comparative geometric-topological calculation of possible conduction pathways for the Li ​+ ​cation in LiRW2O8, where R is a cation M3+. Topological analysis based on Voronoi tessellation was performed using the ToposPro software package. We used two critical sets of parameters to construct conductivity channels. As a result, new sets of complex tungstates with lithium were obtained and analyzed. The influence of the structure and size of a triply charged cation on the possibility of fast migration of a lithium cation is discussed. In conclusion, we offer a list of new promising conductors with the formula LiRW2O8.

Decay Processes in Cationic Alkali Metals in Microsolvated Clusters: A Complex Absorbing Potential Based Equation-of-Motion Coupled Cluster Investigation.

We have employed the highly accurate complex absorbing potential based ionization potential equation-of-motion coupled cluster singles and doubles (CAP-IP-EOM-CCSD) method to study the various intermolecular decay processes in ionized metals (Li+, Na+, K+) microsolvated by water molecules. For the Li atom, the electron is ionized from the 1s subshell. However, for Na and K atoms, the electron is ionized from 2s and both 2s and 2p subshells, respectively. We have investigated decay processes for the Li+-(H2O)n (n = 1-3) systems, as well as Na+-(H2O)n (n = 1, 2), and K+-H2O. The lithium cation in water can decay only via electron transfer mediated decay (ETMD) as there are no valence electrons in lithium. We have investigated how the various decay processes change in the presence of different alkali metal atoms and how the increasing number of water molecules play a significant role in the decay of microsolvated systems. To see the effect of the environment, we have studied Li+-NH3 in comparison to Li+-H2O. In the case of Na+-H2O, we have studied the impact of bond distance on the decay width. The effect of polarization on decay width was checked for the X+-H2O (X = Li, Na) systems. We used the PCM model to study the polarization effect. We have compared our results with existing theoretical and experimental results wherever available in the literature.

Dielectric polymer based electrolytes for high-performance all-solid-state lithium metal batteries

Solid polymer electrolytes (SPEs) are urgently required for achieving practical all-solid-state lithium metal batteries (ASSLMBs) but remain plagued by low ionic conductivity. Herein, we propose a strategy of salt polarization to fabricate a highly ion-conductive SPE by employing a high-dielectric polymer that can interact strongly with lithium salts. Such a polymer with large dipole moments can guide lithium cations (Li+) to be arranged along the chain, forming a continuous pathway for Li+ hopping within the SPE. The as-fabricated SPE, poly(vinylidene difluoride) (PVDF)-LiN(SO2F)2 (LiFSI), has an extraordinarily high dielectric constant (up to 108) and ultrahigh ionic conductivity (0.77 × 10−3 S cm−1). Based on the PVDF–LiFSI SPE, the assembled Li metal symmetrical cell shows excellent Li plating/stripping reversibility at 0.1 mA cm−2, 0.1 mAh cm−2 over 1500 h; the ASS LiFePO4 batteries deliver long-term cycling stability at 1 C over 350 cycles (2.74 mg cm−2) and an ultralong cycling lifespan of over 2600 h (100 cycles) with high loading (11.5 mg cm−2) at 28 °C. First-principles calculations further reveal the ion-dipole interactions-controlled conduction of Li+ in PVDF–LiFSI SPE along the PVDF chain. This work highlights the critical role of dielectric permittivity in SPE, and provides a promising path towards high-energy, long-cycling lifespan ASSLMBs.

Introduction of plumbole to f-element chemistry.

Herein, we present the synthesis and characterization of heteroleptic lanthanide complexes bearing a dianionic η5-plumbole ligand in their coordination sphere. The reaction proceeds via a salt elimination reaction between the dilithioplumbole ([Li(thf)]2[1,4-bis-tert-butyl-dimethylsilyl-2,3-bis-phenyl-plumbolyl] = [Li2(thf)2(η5-LPb)]) and specifically designed [Ln(η8-COTTIPS)BH4] precursors (Ln = lanthanide, La, Ce, Sm, Er; COTTIPS = 1,4-bis-triisopropylsilyl-cyclooctatetraenyl), that are capable of stabilizing a planar plumbole moiety in the coordination sphere of different trivalent lanthanide ions. In-depth ab initio calculations show that the aromaticity of the dianionic plumbole is retained upon coordination. Electron delocalization occurs from the plumbole HOMO to an orbital of mainly d-character at the lanthanide ion. The magnetic properties of the erbium congener were investigated in detail, leading to the observation of magnetic hysteresis up to 5 K (200 Oe s−1), an unequivocal proof for single molecule magnet behavior in this system. The magnetic behavior of the erbium species can be modulated by manipulating the position of the lithium cation in the complex, which directly influences the bonding metrics in the central [(η5-LPb)Er(η8-COTTIPS)]− fragment. This allowed us to assess a fundamental magneto-structural correlation in an otherwise identical inner coordination sphere.

Ion mobility and solvation complexes at liquid–solid interfaces in dilute, high concentration, and localized high concentration electrolytes

Evolution of a lithium cation solvation complex in low concentration electrolytes (LCEs), high concentration electrolytes (HCEs), and localized high concentration electrolytes (LHCEs) reveals competition of transport, desolvation, and deposition events.

Implementation of Synaptic Device Using Ultraviolet Ozone Treated Water‐in‐Bisalt/Polymer Electrolyte‐Gated Transistor

AbstractElectrolyte‐gated transistors (EGTs) have been extensively studied as a next‐generation neuromorphic device mimicking the biological ionic flux in synapses. However, its long‐term plasticity characteristic lasts only for few seconds because of the rapid self‐discharge of electrical double layer. Here, ultraviolet ozone (UVO) treated water‐in‐bisalt (WiBS)/polymer electrolyte‐gated synaptic transistor (WEST) which excellently implements multiple synaptic functions is proposed. Ultraviolet (UV) light and reactive oxygen radicals generated during UVO treatment form trap sites on the surface of active layer, causing lithium cations in the WiBS/polymer electrolyte to be captured at the electrolyte/active layer interface. The UVO treated WEST shows enhanced nonvolatile memory performance for 10 000 s, up to 1186 times longer than that of the untreated WEST. Also, near‐ideal weight update over 10 000 cycle tests with 0.32 and −0.55 nonlinearities of long‐term potentiation and depression is acquired with a ten times improved symmetricity. These results confirm that the surface engineering is a key technique for sophisticated ion transport, and demonstrate various applicability of EGTs as a neuromorphic device.

Mechanisms of ion transport in lithium salt‐doped polymeric ionic liquid electrolytes at higher salt concentrations

AbstractWe used atomistic simulations to study the mechanisms of ion transport in salt‐doped polymeric ionic liquid systems at higher salt concentrations. Consistent with the experimental observations, our simulations indicate that at higher salt concentrations, the anion mobilities become lower than that of the lithium cations. Further, the anion mobilities become relatively insensitive to the salt concentration, while the mobilities of lithium increase with increasing salt concentration. We rationalize the results for the anion mobilities by considering the fractions of anions which are exclusively coordinated with the polycations (Type1); co‐coordinated with cations and lithium (Type2); and those exclusively coordinated with lithium (Type3). By considering the coordination characteristics of the different types of anions and their hopping motions, we demonstrate that the net anion mobilities results from a compensation effect of the salt concentration dependence of the mobilities of the different anions. With respect to the mobilities of the lithium ions, we demonstrate that the latter moves primarily by a structural diffusion mechanism involving refreshing of the solvation shell during hopping. Further, for the majority of the lithium ions, the solvation shell is shown to be comprised of co‐coordinated Type2 anions, and that the number of polycations and the unique polymer chains involved in such coordination decreases with increasing salt concentration. Such changes are shown to weaken the solvation shell around the lithium, thereby facilitating faster ion motion. Together, our results suggest that systems in which the anion which exhibits a stronger coordination to the polycation in comparison to that of the lithium can facilitate higher transference numbers without a concomitant reduction in the mechanical strength.

Lithium and Potassium Cations Affect the Performance of Maleamate-Based Organic Anode Materials for Potassium- and Lithium-Ion Batteries.

In this study we prepared potassium-ion batteries (KIBs) displaying high output voltage and, in turn, a high energy density, as replacements for lithium-ion batteries (LIBs). Organic electrode materials featuring void spaces and flexible structures can facilitate the mobility of K+ to enhance the performance of KIBs. We synthesized potassium maleamate (K-MA) from maleamic acid (MA) and applied as an anode material for KIBs and LIBs, with 1 M potassium bis(fluorosulfonyl)imide (KFSI) and 1 M lithium bis(fluorosulfonyl)imide (LiFSI) in a mixture of ethylene carbonate and ethyl methyl carbonate (1:2, v/v) as respective electrolytes. The K-MA_KFSI anode underwent charging/discharging with carbonyl groups at low voltage, due to the K···O bond interaction weaker than Li···O. The K-MA_KFSI and K-MA_LiFSI anode materials delivered a capacity of 172 and 485 mA h g−1 after 200 cycles at 0.1C rate, respectively. K-MA was capable of accepting one K+ in KIB, whereas it could accept two Li+ in a LIB. The superior recoveries performance of K-MA_LiFSI, K-MA_KFSI, and Super P_KFSI at rate of 0.1C were 320, 201, and 105 mA h g−1, respectively. This implies the larger size of K+ can reversibly cycling at high rate.

Hydrogen and Lithium Bonds-Lewis Acid Units Possessing Multi-Center Covalent Bonds.

MP2/aug-cc-pVTZ calculations were carried out on complexes wherein the proton or the lithium cation is located between π-electron systems, or between π-electron and σ-electron units. The acetylene or its fluorine and lithium derivatives act as the Lewis base π-electron species similarly to molecular hydrogen, which acts as the electron donor via its σ-electrons. These complexes may be classified as linked by π-H∙∙∙π/σ hydrogen bonds and π-Li∙∙∙π/σ lithium bonds. The properties of these interactions are discussed, and particularly the Lewis acid units are analyzed, because multi-center π-H or π-Li covalent bonds may occur in these systems. Various theoretical approaches were applied here to analyze the above-mentioned interactions—the Quantum Theory of Atoms in Molecules (QTAIM), the Symmetry-Adapted Perturbation Theory (SAPT) and the Non-Covalent Interaction (NCI) method.

Plasticized 3D-Printed Polymer Electrolytes for Lithium-Ion Batteries

In the current research, we developed and printed by fused-filament fabrication polylactide-polyethylene-oxide blended membranes. The influence of relative content of polymers on the ease of extrusion and printing processes was studied. Ionic liquid N-butyl-N-methylpyrrolidinium bis(trifluoromethane-sulfonyl)imide (Pyr14TFSI) with dissolved LiTFSI salt was infused into the membranes to produce free-standing films of quasi-solid polymer electrolytes. The printed membranes were characterized by ESEM, DSC, XPS, NMR and EIS methods. Neat-printed PLA (polylactide) membrane exhibited poor wetting and low uptake of ionic liquid. However, the XPS tests of 3D-printed PLA-PEO membrane infused with LiTFSI solvated ionic liquid show evidence of the interaction between lithium cations with both, PEO (polyethylene oxide) and PLA. The measurements of diffusion coefficients by PGSE-NMR suggest that the Li+ ions are coordinated by the PEO segments in the polymer blend. Increase of the PEO content at the expense of PLA polymer, leads to more than one order of magnitude improvement of bulk conductivity, approaching 0.2 mS cm−1 at 60

Ultrathin zwitterionic polymeric interphases for stable lithium metal anodes

<h2>Summary</h2> Lithium metal electrodeposits in the form of irregular morphological features, loosely termed dendrites, on planar anode substrates. The deposits may lead to rapid battery failure and safety concerns. Due to the highly reducing nature of Li (−3.04 V versus standard hydrogen electrode [SHE]), a solid electrolyte interphase (SEI) inevitably forms at the electrode/electrolyte interface, which regulates the subsequent electrodeposition of Li. Rational design of the chemical, mechanical, and ion transport properties of SEI plays an important role in determining the morphology of electrodeposited metals. We report on using initiated chemical vapor deposition (iCVD) to create ultrathin conformal zwitterionic polymeric interphases with precise thicknesses in the range of 10–500 nm. It was found that zwitterionic moieties are able to tune the solvation environment of the lithium cation at the electrode/electrolyte interface, enabling compact, planar deposition of the lithium metal. These findings provide new directions for designing ionic polymeric interphases for metal anodes.

Synthesis and reactivity of an anionic NHC-borane featuring a weakly coordinating silicate anion

We report herein the synthesis of a new NHC-stabilised borane complex featuring a weakly coordinating anion, namely a pentaorganosilicate, on the NHC backbone. The synthesis can be achieved from a zwitterionic abnormal silicate-imidazolium adduct by deprotonation with a strong base followed by quenching with a borane transfer agent. Alternatively, the IPr-BH3 complex can also be deprotonated and the resulting vinylanion is trapped by a tetravalent spirosilane. The first structural data on a lithium derivative of an anionic NHC-borane complex functionalized by a silicate have been obtained and reveal an interaction between the three hydrogens of the borane and the lithium cation. Assessment of the reactivity highlights the higher hydridicity of the anionic NHC-borane compared to the parent IPr-BH3. Finally, electronic properties of this new species have been evaluated by means of DFT calculations and the presence of the silicate on the NHC backbone raises the HOMO which can in part explain the high hydride-donor abilities. This is consistent with the smooth reduction of an aldehyde without Lewis acid additive.

Borate nonlinear optical single crystal surface finishing by argon cluster ion sputtering

Due to its distinctive features, gas cluster ion beams offer unique capabilities to improve the performance of optical devices based on nonlinear single crystals. In this work, the applicability of the argon cluster ion sputtering at different incident energies for finishing the LiB3O5 surface has been studied. It is demonstrated that a combination of high- and low-energy treatment modes (energy per atom of about 100 eV and several eV, respectively) provides an efficient etching rate comparable to that of a monoatomic ion beam. Besides, the surface roughness is reduced to the angstrom level in a wide range of spatial frequencies (ν = 0.3–100 μm–1). Using XPS measurements, the preferential sputtering of oxygen and, to a lesser extent, boron, and an increase in the concentration of lithium cations in both modes were revealed. Although a chemical alteration of the treated materials could not be fully prevented, chemical and physical damages after a cluster bombardment are much less than that from a monoatomic ion beam. .

The Bis(η6 -benzene)lithium Cation: A Fundamental Main-Group Organometallic Species.

The synthesis and characterization of the bis(η6 -benzene)lithium cation, the benzene metallocene of the lightest metal, is reported. The boron compound FmesBCl2 [Fmes: 2,4,6-tris(trifluoromethyl)phenyl] reacted with three molar equivalents of the lithio-acetylene reagent Li-C≡C-Fmxyl [Fmxyl: 3,5-bis(trifluoromethyl)phenyl]. Subsequent crystallization from benzene gave the [bis(η6 -benzene)Li]+ cation with the [{FmesB(-C≡C-Fmxyl)3 }2 Li]- anion. This parent [(arene)2 Li]+ cation shows an eclipsed arrangement of the pair of benzene ligands at the central lithium cation with uniform carbon-lithium bond lengths. The corresponding [(η6 -toluene)2 Li]+ and [(η6 -durene)2 Li]+ containing salts were similarly prepared. The bis(arene)lithium cations were characterized by X-ray diffraction, by solid-state 7 Li MAS NMR spectroscopy and their bonding features were analyzed by DFT calculations.