磷酸三乙酯、丁酸乙酯、N,N二甲基乙酰胺三种试剂的介电常数 与锂离子的结合能 负电荷密度

The advancement of high-voltage solid-state electrolytes constitutes a pivotal challenge for realizing practical solid-state lithium metal batteries (SSLMBs). This work overcomes intrinsic voltage constraints in conventional dimethylformamide-processed poly(vinylidene fluoride) quasi-solid-state polymer electrolytes (SPEs) through molecular engineering of triethyl phosphate (TEP) as a high-band-gap solvent. First-principles calculations demonstrate TEP's exceptional frontier orbital configuration, featuring a 9.4 eV HOMO-LUMO gap, thus expanding the electrochemical window to 4.8 V, an enhancement of 0.5 V compared to DMF-based systems (4.3 V). Leveraging this design, the optimized SPEs enable the stable operation of Li||NCM811 cells at ultrahigh voltages up to 4.7 V. Remarkably, these cells exhibit excellent long-term cycling stability, capacity retentions of 88.2% (1800 cycles at 4.2 V) and 86.8% (900 cycles at 4.5 V) are achieved. Even under the ultrahigh voltage of 4.7 V, the batteries maintain remarkable cycling stability, successfully completing 500 cycles and showcasing exceptional performance. Multiscale analysis reveals dual interfacial stabilization mechanisms: a TEP-derived Li3PO4-rich cathode interphase suppressing structural degradation coupled with a 25 nm crystalline Li2O-dominated anode interphase inhibiting dendrites. This molecular design paradigm establishes a pathway toward 4.7 V-class SSLMBs through interfacial architecture stabilization.

Lithium metal batteries have attracted significant attention due to their promising high energy density. However, the inherent limitations of lithium metal anodes, such as highly reactivity, lithium dendrite growth, and...

Over the past few decades, significant advancements have been made in the development of low‐temperature liquid electrolytes for lithium batteries (LBs). Ongoing exploration of liquid electrolytes is crucial for further enhancing the performance of these batteries. Solvation chemistry plays a dominant role in determining the properties of the electrolyte, significantly affecting LBs performance at low temperatures (LTs). This review introduces solvation structures and their impact, discussing how these structures promote fast desolvation processes and contribute to the improvement of battery performance. Additionally, various solvent strategies are highlighted to refine solvation chemistry at LTs, including the use of linear and cyclic ethers/esters, as well as the role of functional groups within these solvents. The review also summarizes the impact of lithium salts containing organic/inorganic anions on solvation chemistry. Characterization techniques for solvent chemistry are discussed, providing a comprehensive analysis that offers valuable insights for developing next‐generation electrolytes to ensure reliable battery performance across a wide temperature range.

Sluggish lithium (Li) de‐coordination kinetics on the interface hinder the development of high‐energy and low‐temperature Li‐metal batteries (LMBs). In principle, weakly coordinated solvents and anions contribute to improved low‐temperature battery performances due to low Li de‐solvation and de‐anion energy barrier on the anode interface. However, extensive works employ strategies that go against the above‐mentioned principle, commonly using strong coordination strength solvents and anions to facilitate rate and cyclic performances. The in‐depth understanding of this refined Li coordination structure that accelerates Li redox kinetics remains rather elusive. To bridge such gap between theoretical implication and realistic practice of solvent and salt selection, this work examines a model electrolyte involving the strong coordination strength salt (lithium nitrate, LiNO3) and solvent (triethyl phosphate, TEP) to decipher how electron transfer occurred in the cluster solvation impacts Li charge density and dictates Li transport kinetics. One of the critical interpretations is that the electron‐donating nature of LiNO3 reduces the positive charge of Li+, which dampens the interaction between Li+ and TEP ligands. Another key finding is that clustering [LiNO3–Li+–TEP] intensifies the interfacial charge exchange to hasten Li transport kinetics, since anion‐participated cluster solvates exhibit high effective charges than that of anion‐lean Li solvates. This work updates the understanding of why the cluster solvates benefits Li de‐coordination kinetics and hopes to finger out new principles to select Li salts and solvents for better low‐temperature Li metal batteries.

Lithium-based rechargeable batteries have dominated the energy storage field and attracted considerable research interest due to their excellent electrochemical performance. As indispensable and ubiquitous components, electrolytes play a pivotal role in not only transporting lithium ions, but also expanding the electrochemical stable potential window, suppressing the side reactions, and manipulating the redox mechanism, all of which are closely associated with the behavior of solvation chemistry in electrolytes. Thus, comprehensively understanding the solvation chemistry in electrolytes is of significant importance. Here we critically reviewed the development of electrolytes in various lithium-based rechargeable batteries including lithium-metal batteries (LMBs), nonaqueous lithium-ion batteries (LIBs), lithium-sulfur batteries (LSBs), lithium-oxygen batteries (LOBs), and aqueous lithium-ion batteries (ALIBs), and emphasized the effects of interactions between cations, anions, and solvents on solvation chemistry, and functions of solvation chemistry in different types of electrolytes (strong solvating electrolytes, moderate solvating electrolytes, and weak solvating electrolytes) on the electrochemical performance and redox mechanism in the abovementioned rechargeable batteries. Specifically, the significant effects of solvation chemistry on the stability of electrode-electrolyte interphases, suppression of lithium dendrites in LMBs, inhibition of the co-intercalation of solvents in LIBs, improvement of anodic stability at high cut-off voltages in LMBs, LIBs and ALIBs, regulation of redox pathways in LSBs and LOBs, and inhibition of hydrogen/oxygen evolution reactions in LOBs are thoroughly summarized. Finally, the review concludes with a prospective outlook, where practical issues of electrolytes, advanced in situ/operando techniques to illustrate the mechanism of solvation chemistry, and advanced theoretical calculation and simulation techniques such as "material knowledge informed machine learning" and "artificial intelligence (AI) + big data" driven strategies for high-performance electrolytes have been proposed.

… negative surface electrostatic potential. Figure 2 shows the ESP maps of solvating solvents … Based on the above results, we conclude that the electrostatic potential provides an ideal …

Fundamental properties of the Au(111)–KPF6 interface, particularly the potential of zero charge (PZC), exhibit pronounced variations among solvents, yet the origin remains largely elusive. In this study, we aim to link the solvent dependency to the microscopic phenomenon of electron spillover occurring at the metal–solution interface in heterogeneous dielectric media. Addressing the challenge of describing the solvent-modulated electron spillover under constant potential conditions, we adopt a semiclassical functional approach and parametrize it with first-principles calculations and experimental data. We unveil that the key variable governing this phenomenon is the local permittivity within the region approximately 2.5 Å above the metal edge. A higher local permittivity facilitates the electron spillover that tends to increase the PZC on the one hand and enhances the screening of the electronic charge that tends to decrease the PZC on the other. These dual effect lead to a nonmonotonic relationship between the PZC and the local permittivity. Moreover, our findings reveal that the electron spillover induces a capacitance peak at electrode potentials that are more negative than the PZC in concentrated solutions. This observation contrasts classical models predicting the peak to occur precisely at the PZC. To elucidate the contribution of electron spillover to the total capacitance, we decompose the total capacitance into a quantum capacitance of the metal Cq, a classical capacitance of electrolyte solution Cc, and a capacitance Cqc accounting for electron–ion correlations. Our calculations reveal that Cqc is negative due to the promoted electron spillover at more negative potentials. Our work not only reveals the importance of local permittivity in tuning the electron spillover but also presents a viable theoretical approach to study solvent effects on electrochemical interfaces under operating conditions.

Electric double layers are complex systems that involve a wide variety of interactions between the different components of the electrolyte solutions and with the charged interface. While the role of all Coulombic types of interactions is clear, that of the non-Coulombic forces is less obvious. The focus in the present study is on the effect of bulk solvation interactions on the properties of the electric double layer. The analysis is based on classical density functional theory. This approach allows us to account for the correlations between all charged (ionic) and uncharged (solvent) species in the solution. The surface charge at the boundary of the electric double layer is derived from the surface chemistry pertinent to the system. The surface is sensitive to the concentration of potential determining ions, which in turn depends on the correlations and activities of all remaining components. The analysis shows that the solvation forces have a profound effect on the charge and potential distributions in an electric double layer. This is true not just for the solvation of the potential determining ions, but for all species. Even varying the solvent-solvent interaction has a significant impact on the charge and potential distributions in the electric double layer.

… ion transfer As a new method of verification of the theory we suggest investigation of the electrostatic part of the ion transfer energy from one solvent to another. The method of …

Abstract Despite considerable advances in computing power, atomistic simulations under nonperiodic boundary conditions, with Coulombic electrostatic interactions and in systems large enough to reduce finite-size associated errors in thermodynamic quantities to within the thermal energy, are still not affordable. As a result, periodic boundary conditions, systems of microscopic size and effective electrostatic interaction functions are frequently resorted to. Ensuing artifacts in thermodynamic quantities are nowadays routinely corrected a posteriori, but the underlying configurational sampling still descends from spurious forces. The present study addresses this problem through the introduction of on-the-fly corrections to the physical forces during an atomistic molecular dynamics simulation. Two different approaches are suggested, where the force corrections are derived from special potential energy terms. In the first approach, the solvent-generated electrostatic potential sampled at a given atom site is restrained to a target value involving corrections for electrostatic artifacts. In the second approach, the long-range regime of the solvent polarization around a given atom site is restrained to the Born polarization, i.e., the solvent polarization corresponding to the ideal situation of a macroscopic system under nonperiodic boundary conditions and governed by Coulombic electrostatic interactions. The restraints are applied to the explicit-water simulation of a hydrated sodium ion, and the effect of the restraints on the structural and energetic properties of the solvent is illustrated. Furthermore, by means of the calculation of the charging free energy of a hydrated sodium ion, it is shown how the electrostatic potential restraint translates into the on-the-fly consideration of the corresponding free-energy correction terms. It is discussed how the restraints can be generalized to situations involving several solute particles. Although the present study considers a very simple system only, it is an important step toward the on-the-fly elimination of finite-size and approximate-electrostatic artifacts during atomistic molecular dynamics simulations.

… As a function of Li salt in solvents with additives, Li + solvation structure could determine many properties of … Anions and solvent molecules compete to participate in the coordination of …

… carbonate solvents, … solvents for state-of-the-art lithium ion battery electrolytes. The high dielectric constant of the carbonate solvents suggests that the carbonates coordinate to the Li + …

Abstract The solvation structure of Li + plays a significant role in determining the physicochemical properties of electrolytes. However, to date, there is still no clear definition of the solvating power of different electrolyte solvents, and even the solvents that preferentially participate in the solvation structure remain controversial. In this study, we comprehensively discuss the solvating power and solvation process of Li + ions using both experimental characterizations and theoretical calculations. Our findings reveal that the solvating power is dependent on the strength of the Li + ‐solvent (ion‐dipole) interaction. Additionally, we uncover that the anions tend to enter the solvation sheath in most electrolyte systems through Li + ‐anion (ion‐ion) interaction, which is weakened by the shielding effect of solvents. The competition between the Li + ‐solvent and Li + ‐anion interactions ultimately determines the final solvation structures. This insight into the fundamental understanding of the solvation structure of Li + provides inspiration for the design of multifunctional mixed‐solvent electrolytes for advanced batteries.

The structural and electrochemical properties of lithium (Li) ion complexes in concentrated electrolytes based on acetonitrile (AN) and tris(2,2,2-trifluoroethyl) phosphate (TFEP) as solvents and LiTFSA [TFSA: bis(trifluoromethanesulfonyl)amide] as a Li salt were investigated by employing electrochemical measurements, vibrational spectroscopy, and high-energy X-ray total scattering (HEXTS) with all-atom molecular dynamics (MD) simulations. Via electrochemical measurements, reversible Li-ion insertion/deinsertion into/from the graphite electrode was observed in concentrated LiTFSA/AN solutions but not in concentrated LiTFSA/TFEP solutions. The experimental radial distribution functions [Gexp(r)] derived from HEXTS were successfully represented by the corresponding MD-derived values [GMD(r)] for both AN- and TFEP-based electrolyte systems. We found that (1) in the dilute system, Li ions were solvated with only solvent molecules in AN-based solutions to form a completely dissociated [Li(AN)4]+ complex, while...

Abstract The building of safe and high energy-density lithium batteries is strongly dependent on the electrochemical performance of working electrolytes, in which ion–solvent interactions play a vital role. Herein, the ion–solvent chemistry is developed from mono-solvent to multi-solvent complexes to probe the solvation structure and the redox stability of practical electrolytes. The decrease in energies of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of solvents in lithium-ion solvation shells becomes less significant as the number of coordinated solvents increases, but both the HOMO and LUMO energies of the coordinated solvents remain lower than those of free solvents. A positive and approximately linear relationship was found between the decrease in the HOMO/LUMO energy and the average binding energy between Li+ and the coordinated solvents. A binary-solvent complex model further highlight the significant importance of the electrolyte solvation environment in regulating electrolyte stability, and it is essential to consider electrolyte stability from the perspective of ion–solvent complexes. These fresh insights into the energy chemistry of multi-solvent complexes provide critical references for electrolyte design and cell optimization.

ConspectusBuilding high-energy-density batteries is urgently demanded in contemporary society because of the continuous increase in global energy consumption and the quick upgrade of electronic devices, which promotes the use of high-capacity lithium metal anodes and high-voltage cathodes. Achieving a stable interface between electrolytes and highly reactive electrodes is a prerequisite to constructing a safe and powerful battery, in which electrolyte regulation plays a decisive role and largely determines the long-term and rate performances. The bulk and interfacial properties of electrolytes are directly determined by the fundamental interactions and the as-derived microstructures in electrolytes. Different from experimental trial-and-error approaches, the rational bottom-up design of electrolytes based on a comprehensive and deep understanding of the fundamental interactions between electrolyte compositions and the structure-function relationship is highly expected to accelerate breaking through the bottleneck in current technology and realizing next-generation Li batteries.In this Account, we afford an overview of our recent attempts toward rational electrolyte design for safe Li batteries based on a comprehensive understanding of the cation-solvent, cation-anion, and anion-solvent interactions in electrolytes. The formation of cation-solvent complexes decreases the reductive stability but increases the oxidative stability of solvent molecules according to frontier molecular orbital theory, whereas the introduction of anions into the Li+ solvation shell has the opposite function in regulating solvent stability compared with cations. The competitive coordination of anions and solvent molecules with cations directly determines the salt solubility in electrolytes and the formation of ion pairs and aggregates, which widely exist in high-concentration electrolytes and stabilize Li metal anodes. An easy and effective route to dissolve lithium nitrate in ester electrolytes is accordingly proposed. Although anions are hardly solvated in routine solvents, solvents with a high acceptor number or an exposed positive charge site are highly expected to enhance the anion-solvent interaction. The solvation of anions will have a strong influence on electrolytes, including regulating the electrolyte solvation structure and stability, increasing the cation transference number, and promoting salt dissociation. The emerging Li bond theory and big-data approaches, combined with first-principles calculations and experimental characterizations, are also expected to promote rational electrolyte design with much reduced time and expense.Collectively, with a comprehensive and deep understanding of the fundamental interactions in electrolytes and the structure-function relationship, bottom-up engineering of Li battery electrolytes is expected to be achieved, accelerating the applications of safe high-energy-density Li batteries. The general principles demonstrated in Li batteries are also supposed to be applicable to other battery systems and even universal electrochemistry in solutions, including fuel cells and various electrocatalyses.

… of solvents are commonly used in nonaqueous lithium battery electrolytes. Structures comprised of the solvents and ions … Solvation structures which could exist in the electrolyte include …

… The optimal solvent-anion combination should strike a balance, producing a … lithium ions with moderate coordination strength. In this work, we systematically established co-solvents …

… on the coordination characteristics of lithium ion in EC solvent is, therefore, necessary. … the coordination chemistry of lithium ion in EC solvent by studying the structures and stability of [Li(…

… Lithium ion batteries (LIBs… structure of Li + in different types of solvents, we found a close correlation between the formation of an AI-ISC structure and the coordination number of solvents…

Abstract Electrolytes are known as the dominant factors for fast‐charging affordability and low‐temperature capability of lithium‐ion batteries (LIBs). Unfortunately, the current electrolytes can hardly simultaneously satisfy all the required characteristics, including sufficient ion transport, high oxidation/reduction interfacial stability, and fast de‐solvation process over a wide‐temperature range. Here, we report a solution by designing electrolyte solvents that coordinate with Li + in steric configuration. The steric coordinated electrolytes (SCEs) can overcome the dilemma of quasi‐planer coordinated ether electrolytes that has to be weakly coordinated with Li + to avoid solvent co‐intercalation towards graphite (Gr) anode, therefore enabling the merits including sufficiently dissociation of Li‐salt with high ionic conductivity, low de‐solvation energy, and forming electrode‐electrolyte interphase with low energy barrier. As results, the SCEs with only single‐salt and single‐solvent (trimethoxymethane) achieve fast kinetics towards Gr anode and high oxidation stability. The LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811)||Gr LIBs can reach 80% state of the charge in 6 min, and the Ah‐level energy‐dense pouch cells (4.5 V) retain 82.96% (500 cycles) and 85.94% (200 cycles) of initial capacities at room temperature and −20 °C, respectively. Our work deepens the fundamental understanding of Li‐ion solvation structures and affords an effective approach to design sustainable fluro‐free electrolytes for battery systems.

… with conclusions from previous studies of solvent–Li + and anion–Li + binding energies. It is also important that the solvent–Li + binding energies are adequately predicted using the …

… quantum chemistry calculations. The coordination of the carbonyl oxygen of the solvents to … populations of the cis–cis and cis–trans conformers of DMC in the lithium ion solvation shell. …

… predicts the binding … Quantum chemistry calculations performed on solvent−ion clusters reveal that the energy for EC substitution with DMC decreases with increasing number of solvent …

… reduce the binding energy of solvent-solvent complexes in … wide applications in conventional lithium ion batteries. As results, … DFT calculations as well as experimental verifications. The …

Lithium-ion batteries (LIBs) represent the state of the art in high-density energy storage. To further advance LIB technology, a fundamental understanding of the underlying chemical processes is required. In particular, the decomposition of electrolyte species and associated formation of the solid electrolyte interphase (SEI) is critical for LIB performance. However, SEI formation is poorly understood, in part due to insufficient exploration of the vast reactive space. The Lithium-Ion Battery Electrolyte (LIBE) dataset reported here aims to provide accurate first-principles data to improve the understanding of SEI species and associated reactions. The dataset was generated by fragmenting a set of principal molecules, including solvents, salts, and SEI products, and then selectively recombining a subset of the fragments. All candidate molecules were analyzed at the ωB97X-V/def2-TZVPPD/SMD level of theory at various charges and spin multiplicities. In total, LIBE contains structural, thermodynamic, and vibrational information on over 17,000 unique species. In addition to studies of reactivity in LIBs, this dataset may prove useful for machine learning of molecular and reaction properties. Measurement(s) molecule • solid electrolyte interphase Technology Type(s) density functional theory • computational modeling technique Factor Type(s) bond type • charge • spin multiplicity Measurement(s) molecule • solid electrolyte interphase Technology Type(s) density functional theory • computational modeling technique Factor Type(s) bond type • charge • spin multiplicity Machine-accessible metadata file describing the reported data: https://doi.org/10.6084/m9.figshare.14915256

… 2a, the computed binding enthalpies of Li + cation with all solvent molecules show good … the binding enthalpies of Na + and K + cations with the solvent molecules. Thus, the binding …

… for all solvent charge cases results from the first four solvent … free energy calculations with quasi-chemical theory (see … the binding energy and cancellation of packing and chemical …

… This paper focuses on the use of implicit solvent in electrochemical density functional theory (DFT) calculations. We investigate both the necessity and limits of an implicit solvent …

… Lithium-ion secondary batteries with liquid and gel … in the solvent dipole moment with molecular geometry upon solvent/Li + … /solvent binding energetics from MM and quantum chemistry …

When a Li–metal electrode immerses in the electrolytes containing organic solvents, it is … Therefore, the self-consistent-charge density functional tight-binding (SCC-DFTB) approach …

… solvation characteristics of the lithium ion for a given solvent. … states of “bound” and “free”, as carbonate solvents in transition … state (bound), the ion is surrounded by a number of solvent …

… calculate the complexation energies by quantum chemical … (used, eg, to calculate the binding energies of Li + −diglyme … −solvent complexes with quantum-chemical calculations we …

… This paper calculates the binding energies of the solvents to Li using molecular quantum mechanics (MQM) techniques. The binding energies of the various solvents to Li + determine …

Conceptually, single-ion polymer electrolytes (SIPE) with the anion bound to the polymer could solve major issues in Li-ion batteries, but their conductivity is too low. Experimentally, weakly interacting anionic groups have the best conductivity. To provide a theoretical basis for this result, density functional theory calculations of the optimized geometries and energies are performed for charged ligands used in SIPE. Comparison is made to neutral ligands found in dual-ion conductors, which demonstrate higher conductivity. The free energy differences between adding and subtracting a ligand are small enough for the neutral ligands to have the conductivity seen experimentally. However, charged ligands have large barriers, implying that lithium transport will coincide with the slow polymer diffusion, as observed in experiments. Overall, SIPE will require additional solvent to achieve a sufficiently high conductivity. Additionally, the binding of mono- and bidentate geometries varies, providing a simple and clear reason that polarizable force fields are required for detailed interactions.

Organic carbonates and their mixtures are frequently used in electrolyte solutions in lithium-ion batteries. Rationalization and tuning of the related Li+ solvation processes are rooted in the proper identification of the representative low-energy spatial structures of the microsolvated Li+(S)n clusters. In this study, we introduce an automatically generated database of conformational energies (CEs), LICARBCONF806, comprising 806 diverse conformers of Li+ clusters with 7 common organic carbonates. A number of standard and composite density functional theory (DFT) approaches and fast semi-empirical methods are examined to reproduce the reference CEs obtained at the RI-SCS-MP2/CBS level of theory. A hybrid PBE0-D4 functional paired with the def2-QZVP basis set is the most robust in reproducing the reference values while composite B97-3c demonstrates the best cost-benefit ratio. Contemporary tight-binding semi-empirical methods GFNn-xTB can be used for the filtering of high-energy structures, but their performance worsens significantly when the limited number of low-energy (CE < 3 kcal mol-1) conformers are to be sorted. Thermal corrections used to convert electronic energies to respective Gibbs free energies and especially corrections imposed by a continuum solvation model can significantly influence both the conformer ranking and the width of the CE distribution. These should be appropriately taken into account to identify lowest energy conformers in solution and at non-zero temperatures. The almost black-box conformation generation workflow used in this work successfully predicts representitative low-energy four-coordinated conformers of Li+ clusters with cyclic carbonates and unravels the complex conformational nature of the clusters with flexible linear carbonates.

Lithium metal batteries (LMBs) are regarded as one of the most promising candidates for next‐generation energy storage systems owing to their exceptionally high theoretical energy density and low redox potential. However, their practical implementation remains severely limited by the instability of the solid electrolyte interphase (SEI), which arises from the intrinsic chemical reactivity of lithium metal with electrolyte components. To elucidate the molecular origins of SEI instability and identify electrolyte design principles, we employed a microscopic approach combining density functional theory and ab initio molecular dynamics simulations. Three typical linear organic solvents—namely dimethyl carbonate, ethyl acetate, and 1,2‐dimethoxyethane—were systematically examined to represent carbonate‐, ester‐, and ether‐based electrolytes. Our results reveal that the solvent dielectric constant critically governs both Li+ solvation strength and the frontier molecular orbital energies of the salt anion, thereby determining interfacial reduction pathways. Based on these insights, we propose an optimal dielectric constant window that simultaneously balances solvation capability and reduction stability. This work establishes the solvent dielectric constant as a physically meaningful descriptor that links molecular‐scale solvation chemistry with macroscopic electrochemical performance, offering a rational design strategy for stable and efficient electrolytes in LMBs.

Solvation and association of ions in solutions largely depend on the dielectric properties of the solvent, the distance between ions in solutions, and temperature. This paper considers the effect of temperature on static dielectric constant (DC), dipole dielectric relaxation (DR) time, and limiting (ultimate) high frequency (HF) electrical conductivity (EC) of water and some polar solvents. In the investigated temperature range (0–370 °C), the static DC and DR time of water decrease, and limiting HF EC passes through a maximum at 250–300 °C with temperature growth. The dielectric characteristics of methanol, ethanol, and propanol behave in a similar way. It is shown that the existence of an HF EC temperature maximum is due to the different nature of the temperature dependences of DC and DR time. It is suggested that the same dependences are responsible for the presence of a maximum in the temperature dependences of the dissociation degree and the ionic product of water. The influence of non-electrolytes concentration as well as metal salts on the dielectric properties of their aqueous solutions is considered. The limiting HF EC of water determines the specific EC value of aqueous electrolyte solutions. Analysis of the absorption of microwave energy by polar solvents, as well as aqueous solutions of non-electrolytes and electrolytes, at a frequency of 2455 MHz is carried out. The optimal conditions for high-frequency heating of solutions have been established. The distance between ions in aqueous solutions of inorganic salts and in non-aqueous solutions of ionic liquids is calculated. It is shown that the maximum on the concentration dependence of the specific EC can be related to ions association.

… Clearly, knowledge of the solvent dielectric constant is a prerequisite for accurate solvation modeling. It is therefore hoped that the solution properties reported in this work will lay the …

… In the present study, however, the decrease in dielectric constant with DME was significant while the complexing ability of DME to the Li+ ion was rather weak. So we had to take the …

We report the dielectric constant of 1 M LiPF6 in EC:EMC 3:7 w/w (ethylene carbonate/ethyl methyl carbonate) in addition to neat EC:EMC 3:7 w/w. Using three Debye relaxations, the static permittivity value, or dielectric constant, is extrapolated to 18.5, which is compared to 18.7 for the neat solvent mixture. The EC solvent is found to strongly coordinate with the Li+ cations of the salt, which results in a loss of dielectric contribution to the electrolyte. However, the small amplitude and large uncertainty in relaxation frequency for EMC cloud definitive identification of the Li+ solvation shell. Importantly, the loss of the free EC permittivity contribution due to Li+ solvation is almost completely balanced by the positive contribution of the associated LiPF6 salt, demonstrating that a significant quantity of dipolar ion pairs exists in 1 M LiPF6 in EC:EMC 3:7.

Sluggish evolution of lithium ions’ solvation sheath induces large charge‐transfer barriers and high ion diffusion barriers through the passivation layer, resulting in undesirable lithium dendrite formation and capacity loss of lithium batteries, especially at low temperatures. Here, an ion‐dipole strategy by regulating the fluorination degree of solvating agents is proposed to accelerate the evolution of the Li+ solvation sheath. Ethylene carbonate (EC)‐based fluorinated derivatives, fluoroethylene carbonate (FEC) and di‐fluoro ethylene carbonate (DFEC) are used as the solvating agents for a high dielectric constant. As the increase of the fluorination degree from EC to FEC and DFEC, the Li+‐dipole interaction strength gradually decreases from 1.90 to 1.66 and 1.44 eV, respectively. Consequently, the DFEC‐based electrolyte displays six times faster ion desolvation rate than that of a non‐fluorinated EC‐based electrolyte at −20 °C. Furthermore, LiNi0.8Co0.1Mn0.1O2||lithium cells in a DFEC‐based electrolyte retain 91% original capacity after 300 cycles at 25 °C, and 51% room‐temperature capacity at −30 °C. By bridging the gap between the ion‐dipole interactions and the evolution of Li+ solvation sheath, this work provides a new technique toward rational design of electrolyte engineering for low‐temperature lithium batteries.

Electrolyte engineering for long‐lifespan alkali‐based batteries focuses on modulating the solvation structure to build the electrode/electrolyte interface and dictate interfacial reactions. Previous strategies have relied on increasing the salt concentration to introduce the anion‐derived solid electrolyte interphase (SEI) for considerable interfacial stability, but these strategies are restricted by the poor solubility of film‐forming salts in weak solvation electrolytes. Herein, a dielectric increment of weak solvation electrolytes based on the ion dissociation and association chemistry is proposed to realize the high salt solubility. Differing from the dielectric decrement with the addition of salts in strong solvation electrolytes owing to reduced free solvents, the dielectric increment in weak solvation electrolytes is a result of the surplus dielectric polarization of contact ion pairs (CIPs). As a demonstration in salt‐concentration‐sensitive lithium–sulfur (Li–S) batteries, CIPs facilitate the high solubility of lithium polysulfides (LiPSs) and promote the Li2S2/Li2S nucleation. The CIP‐induced dielectric increment of electrolytes yields 96% capacity retention after 175 cycles at 0.2 C in the Li–S cell. This underexplored strategy provides effective guidelines for the design of dielectric‐constant‐mediated electrolytes for alkali‐based battery applications.

Abstract The dielectric constant is a crucial physicochemical property of liquids in tuning solute–solvent interactions and solvation microstructures. Herein the dielectric constant variation of liquid electrolytes regarding to temperatures and electrolyte compositions is probed by molecular dynamics simulations. Dielectric constants of solvents reduce as temperatures increase due to accelerated mobility of molecules. For solvent mixtures with different mixing ratios, their dielectric constants either follow a linear superposition rule or satisfy a polynomial function, depending on weak or strong intermolecular interactions. Dielectric constants of electrolytes exhibit a volcano trend with increasing salt concentrations, which can be attributed to dielectric contributions from salts and formation of solvation structures. This work affords an atomic insight into the dielectric constant variation and its chemical origin, which can deepen the fundamental understanding of solution chemistry.

… In DMC, the formation of an important fraction of ion pairs is expected as the dielectric constant of this solvent is very low. This fraction should increase significantly with the molality of …

Lithium (Li) metal anode holds great promise for next-generation high-energy-density batteries, while the insufficient fundamental understanding of the complex solid electrolyte interphase (SEI) is the major obstacle for the full demonstration of their potentials in working batteries. The characteristics of SEI highly depend on the inner solvation structure of lithium ions (Li+). In this contribution, we clarify the critical significance of cosolvent properties on both Li+ solvation structure and the SEI formation on working Li metal anodes. Universally, non-solvating and low-dielectricity (NL) cosolvents intrinsically enhance the interaction between anion and Li+ by affording a low dielectric environment. The abundant positively-charged anion-cation aggregates generated as the introduction of NL cosolvents are preferentially brought to the negatively-charged Li anode surface, inducing an anion-derived inorganic-rich SEI. A solvent diagram is further built to illustrate that a solvent with both proper relative binding energy toward Li+ and dielectric constant is suitable as NL cosolvent. This work elucidates the significance of fundamental physicochemical theory in guiding electrolyte design and calls for more efforts to rationally apply the cosolvents for stable Li metal batteries.

… change but to an increase in the solvation ability of the mixed … the lithium ion in the mixed solvents while the PMBP - ion … in alcohols of moderate dielectric constant. The Journal of …

… , molecular simulations can be performed at a drastically reduced computational cost, enabling the computational … The set of macroscopic properties of an IL is directly dependent on the …

… value of this reaction is called "donor number" or "donicity" (… for the description of cation-EPD-solvent interactions in that it … of the electron-pair donor (the solvent molecule) can be used …

… constant or donor number of the solvent or … donor number is more effective than dielectric constant in controlling ion-solvating ability of polymers, and that the cation transference number …

… cation–solvent interaction became stronger than the cation–… Gutmann donor number, [Ti(OH)(H 2 O) 5 ] 2+ cations were … smaller Gutmann donor number in binary solvents, which is in …

… at understanding the effect of solvent (H 2 O) on subtle interactions, such as cation−π, and … gas phase to solvent phase. Li + , K + , and Mg 2+ ions are considered as cations, and high …

Donor number (DN) serves as a metric for describing the basicity of a solvent or anion and delineates the tendency to donate electrons to electron acceptors. In this review, we...

Parameters that provide a quantitative description of the free energy of interaction of cations with any H-bond acceptor in any solvent have been experimentally determined.

… the anionic and cationic components of the ionic liquid. The data are presented and correlated with other solvent parameters and compared to donor numbers reported by other groups. …

… the donicity or donor number (DN) to describe the nucleophilic behaviour and the acceptor number (AN) to describe electrophilic behaviour on the part of the solvent. Numerous semi-…

Divalent-cation-based batteries are being considered as potential high energy density storage devices. The optimization of electrolytes for these technologies is, however, still largely lacking. Recent demonstration of the feasibility of Ca and Mg plating and stripping in the presence of a passivation layer or an artificial interphase has paved the way for more diverse electrolyte formulations. Here, we exhaustively evaluate several Ca-based electrolytes with different salts, solvents, and concentrations, via measuring physicochemical properties and using vibrational spectroscopy. Some comparisons with Mg- and Li-based electrolytes are made to highlight the unique properties of the Ca2+ cation. The Ca-salt solubility is found to be a major issue, calling for development of new highly dissociative salts. Nonetheless, reasonable salt solubility and dissociation are achieved using bis(trifluoromethanesulfonyl)imide (TFSI), BF4, and triflate anion based electrolytes and high-permittivity solvents, such as ethylene carbonate (EC), propylene carbonate (PC), γ-butyrolactone (gBL), and N,N-dimethylformamide (DMF). The local Ca2+ coordination is concentration-dependent and rather complex, possibly involving bidentate coordination and participation of the nitrogen atom of DMF. The ionicity and the degree of ion-pair formation are both investigated and found to be strongly dependent on the nature of the cation, solvent donicity, and salt concentration. The large ion–ion interaction energies of the contact ion pairs, confirmed by density functional theory (DFT) calculations, are expected to play a major role in the interfacial processes, and thus, we here provide electrolyte design strategies to engineer the cation solvation and possibly improve the power performance of divalent battery systems.

The use of concentrated aprotic electrolytes in lithium batteries provides numerous potential applications, including the use of high-voltage cathodes and Li-metal anodes. In this paper, we aim at understanding the effect of salt concentration on the variation of the Li/Li+ Quasi-Reference Electrode (QRE) potential in Tetraglyme (TG)-based electrolytes. Comparing the obtained results to those achieved using Dimethyl sulfoxide DMSO-based electrolytes, we are now able to take a step forward and understand how the effect of solvent coordination and its donor number (DN) is attributed to the Li-QRE potential shift. Using a revised Nernst equation, the alteration of the Li redox potential with salt concentration was determined accurately. It is found that, in TG, the Li-QRE shift follows a different trend than in DMSO owing to the lower DN and expected shorter lifespan of the solvated cation complex.

… We believe that the most important solvent properties affecting chemical reactivity are anion-solvating tendency and cation-solvating tendency. We shall symbolize these …

A large number of quantitative studies have been made of the Gibbs energy of transfer (the solvent medium effect) for cations transferring from water into mixed aqueous−organic solvent systems, mainly at 25 °C. Nevertheless, no systematic effort appears to have been made to compile and analyze these data, particularly for multivalent cations. A critical review of this information and its presentation in a manner that permits comparison of different cations in a given solvent mixture and of a given cation transferring into different mixtures is therefore of value.

… the pair interaction of a donor B and an acceptor A (cation in our case). The higher the donor and … 3+ on the donor numbers of solvents, we used the data obtained for the reduction of Al …

Passivation of the magnesium (Mg) anode in the chloride-free electrolytes using commercially available Mg salts is a critical issue for rechargeable Mg batteries. Herein, a high donor number cosolvent of 1-methylimidazolium (MeIm) is introduced into Mg(TFSI)2- and Mg(HMDS)2-based electrolytes to address the passivation problem and realize highly reversible Mg plating/stripping. Theoretical calculations and experimental characterization results reveal that the strong coordination ability of MeIm with Mg2+ can weaken the anion-cation interactions and promote the formation of free anions that have higher reduction stability, thus significantly suppressing anion-derived passivation layer formation. By adding MeIm cosolvent into Mg(TFSI)2-based electrolyte, the average Coulombic efficiency of the Mg//Cu cell is increased from less than 20% to over 90%, and the Mg//Mg cell can stably cycle for over 800 h with a low overpotential. In the MeIm-regulated Mg(HMDS)2-based electrolyte, the solvation structure change, featured by an effective separation of Mg2+ and HMDS-, greatly increases the ionic conductivity by more than 30 times. This solvation structure regulation strategy for noncorrosive electrolytes of commercially available Mg salts has a great potential for application in future rechargeable Mg metal batteries.

… parameter and the Gutmann donor number, respectively. The … of solvent interactions (Qq) vary considerably with cation size. … cation size, being the most negative for the largest cation …