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Single‐ion conducting (SIC) polymers, wherein anions are covalently bonded to the polymer chain, selectively facilitate the movement of lithium ions, making them promising polymer electrolytes for lithium‐ion batteries because only lithium ion acts as a charge carrier. Carboxylate‐type SIC polymers offer cost advantages and are facilely prepared compared to conventional types like sulfonylamide‐type SIC polymers. However, they are known to suffer from inefficient dissociation of lithium ions due to their high basicity. In this study, enhancement of lithium‐ion dissociation in carboxylate‐type SIC polymers is investigated by complexing them with ionic liquid (IL). Incorporation of IL with the SIC polymer significantly improves electrochemical properties, achieving a high ionic conductivity close to 2 mS cm−1 and a critical current density of 2.1 mA cm−2 in a Li symmetric cell at 25 °C. The interaction between the SIC polymer and IL is confirmed through infrared and Raman spectroscopy. Electrochemical tests of the Li/LiFePO4 cell exhibit a high reversible capacity of 128.6 mAh g−1 with a cycle retention of 89.9 % after 100 cycles at 1 C (1 C=170 mA g−1) and an excellent recuperation even after rate tests at 6 C. [ABSTRACT FROM AUTHOR]

The electrolytes for lithium metal batteries (LMBs) are plagued by a low Li+ transference number (T+) of conventional lithium salts and inability to form a stable solid electrolyte interphase (SEI). Here, we synthesized a self‐folded lithium salt, lithium 2‐[2‐(2‐methoxy ethoxy)ethoxy]ethanesulfonyl(trifluoromethanesulfonyl) imide (LiETFSI), and comparatively studied with its structure analogue, lithium 1,1,1‐trifluoro‐N‐[2‐[2‐(2‐methoxyethoxy)ethoxy)]ethyl]methanesulfonamide (LiFEA). The special anion chemistry imparts the following new characteristics: i) In both LiFEA and LiETFSI, the ethylene oxide moiety efficiently captures Li+, resulting in a self‐folded structure and high T+ around 0.8. ii) For LiFEA, a Li−N bond (2.069 Å) is revealed by single crystal X‐ray diffraction, indicating that the FEA anion possesses a high donor number (DN) and thus an intensive interphase "self‐cleaning" function for an ultra‐thin and compact SEI. iii) Starting from LiFEA, an electron‐withdrawing sulfone group is introduced near the N atom. The distance of Li−N is tuned from 2.069 Å in LiFEA to 4.367 Å in LiETFSI. This alteration enhances ionic separation, achieves a more balanced DN, and tunes the self‐cleaning intensity for a reinforced SEI. Consequently, the fast charging/discharging capability of LMBs is progressively improved. This rationally tuned anion chemistry reshapes the interactions among Li+, anions, and solvents, presenting new prospects for advanced LMBs. [ABSTRACT FROM AUTHOR]

Constructing anion-derived solid electrolyte interphase (SEI) by recruiting anions into the solvation sheath of Li+ is extremely conducive to restrain the dendrite growth of Li metal anode. However, the presence of anions in the solvation sheath of Li+ is severely hindered by the solvents with strong coordinating ability in conventional electrolyte. Herein, we boost the content of anions in the primary solvation sheath of Li+ by employing a solvent with low donor number, 2-methyltetrahydrofuran, inducing an anion-derived SEI. As a result, the Li∥Cu cells show a high average Coulombic efficiency (> 99%) over 500 cycles and the Li∥LiFePO4 cells under a low negative/positive capacity ratio of 2:1 exhibit an impressive capacity retention of 90% after 100 cycles. This work provides insights on constructing stable anion-derived SEI and offers guidance in designing electrolytes for stable Li metal batteries. [ABSTRACT FROM AUTHOR]

The performance of aqueous Zn ion batteries (AZIBs) is highly dependent on inner Helmholtz plane (IHP) chemistry. Notorious parasitic reactions containing hydrogen evolution reactions (HER) and Zn dendrites both originate from abundant free H2O and random Zn deposition inside active IHP. Here, we report a universal high donor number (DN) additive pyridine (Py) with only 1 vol. % addition (Py‐to‐H2O volume ratio), for regulating molecule distribution inside IHP. Density functional theory (DFT) calculations and molecular dynamics (MD) simulation verify that incorporated Py additive could tailor Zn2+ solvation sheath and exclude H2O molecules from IHP effectively, which is in favor of preventing H2O decomposition. Consequently, even at extreme conditions such as high depth of discharge (DOD) of 80 %, the symmetric cell based on Py additive can sustain approximately 500 h long‐term stability. This efficient strategy with high DN additives furnishes a promising direction for designing novel electrolytes and promoting the practical application of AZIBs, despite inevitably introducing trace organic additives. [ABSTRACT FROM AUTHOR]

Among the next-generation energy storage technologies, lithium-sulfur batteries are considered one of the most appealing solutions owing to their remarkable theoretical capacity. However, to become commercially competitive, there is a strong need to address some issues still characterizing this technology. One of the explored strategies is the optimization of the electrolyte formulation. To this aim, we compared 1,3-dioxolane/1,2-dimethoxyethane-based electrolytes containing two lithium halides, i.e., lithium bromide (LiBr) and lithium iodide (LiI), with lithium bis (trifluoromethane)sulfonylimide (LiTFSI) as a reference electrolyte. The obtained results show how the donicity of the lithium-salt anions might affect the solid electrolyte interphase stability and the lithium sulfide deposition morphology, therefore influencing the electrochemical performance of the cells. Among the tested electrolytes, the sulfur cell containing LiBr salt exhibited the best electrochemical performance maintaining a specific capacity of 900 mAh g−1 at C/4 and a stable trend along cycling at 1C with a specific capacity of about 770 mAh g−1 for 200 cycles. [ABSTRACT FROM AUTHOR]

The electrolytes in energy-dense lithium metal batteries (LMBs) face the challenge of being compatible with both the lithium anode and the high voltage cathodes. Adjusting the solvation structures of the electrolytes by regulating the interaction between ions and solvents is an effective strategy to improve the stability of LMBs. Herein, lithium trifluoroacetate (LiTFA) endowed with high donor number is introduced into ether-based electrolytes as an additive to regulate the solvation structure and further stabilize the interphase as well as accelerate the interfacial kinetic of LMBs. Due to the strong interaction between TFA - with Li + , the anion-rich solvation structure with reduced solvent coordination capability is constructed, contributing to the formation of inorganic-rich interphase layers and facilitate charge transfer reaction. Consequently, the designed electrolyte improves the reversibility of Li plating/stripping with high Coulombic efficiency of 99.24% and enables long-term cycling of Li||LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) over 100 cycles with a capacity retention of 84.37% under the condition of lean electrolyte, limited Li source and conventional Li-salt concentration. This work provides an effective and low-cost strategy to adjust the solvation structure and improve the stability of LMBs without largely sacrificing the intrinsic physicochemical property (viscosity, wettability, ionic conductivity etc.) of electrolytes., (© 2024 Wiley‐VCH GmbH.)

Among the next-generation energy storage technologies, lithium-sulfur batteries are considered one of the most appealing solutions owing to their remarkable theoretical capacity. However, to become commercially competitive, there is a strong need to address some issues still characterizing this technology. One of the explored strategies is the optimization of the electrolyte formulation. To this aim, we compared 1,3-dioxolane/1,2-dimethoxyethane-based electrolytes containing two lithium halides, i.e., lithium bromide (LiBr) and lithium iodide (LiI), with lithium bis (trifluoromethane)sulfonylimide (LiTFSI) as a reference electrolyte. The obtained results show how the donicity of the lithium-salt anions might affect the solid electrolyte interphase stability and the lithium sulfide deposition morphology, therefore influencing the electrochemical performance of the cells. Among the tested electrolytes, the sulfur cell containing LiBr salt exhibited the best electrochemical performance maintaining a specific capacity of 900 mAh g−1 at C/4 and a stable trend along cycling at 1C with a specific capacity of about 770 mAh g−1 for 200 cycles.

Lithium-oxygen (Li-O 2 ) batteries have obtained widespread attention as next-generation energy storage systems due to their extremely high energy density. However, the high charge overpotential, attributed to the insulating property of Li 2 O 2 , significantly limits the energy efficiency and triggers solvent degradation. The high electrochemical activities of oxygen reduction reactions (ORR) and oxygen evolution reactions (OER) on the cathode are crucial for alleviating the high charging polarizations and enhancing the lifetime of Li-O 2 batteries, which are also top challenges of state-of-art research. In this review, the scientific challenges and the proposed solutions in the development of cathode catalysts have been summarized. The recent research advancements on the nanoengineering of cathode catalysts for Li-O 2 batteries have been comprehensively discussed, and the perspectives on the structure optimization are presented. Meanwhile, we have elucidated the structure-performance relationship between the electronic state and performance of the cathode catalysts at the nanoscale level. This review intends to provide guidelines for the design and construction of cathode catalysts in advanced Li-O 2 batteries.

Solvent engineering by Lewis‐base solvent and anti‐solvent is well known for forming uniform and stable perovskite thin films. The perovskite phase crystallizes from an intermediate Lewis‐adduct upon annealing‐induced crystallization. Herein, it is explored the effects of trimethyl phosphate (TMP), as a novel aprotic Lewis‐base solvent with a low donor number for the perovskite film formation and photovoltaic characteristics of perovskite solar cells (PSCs). As compared to dimethylsulfoxide (DMSO) or dimethylformamide (DMF), the usage of TMP directly crystallizes the perovskite phase, i.e., reduces the intermediate phase to a negligible degree, right after the spin‐coating, owing to the high miscibility of TMP with the anti‐solvent and weak bonding in the Lewis adduct. Interestingly, the PSCs based on methylammonium lead iodide (MAPbI3) derived from TMP/DMF‐mixed solvent exhibit a higher average power conversion efficiency of 19.68% (the best: 20.02%) with a smaller hysteresis in the current‐voltage curve, compared to the PSCs that are fabricated using DMSO/DMF‐mixed (19.14%) or DMF‐only (18.55%) solvents. The superior photovoltaic properties are attributed to the lower defect density of the TMP/DMF‐derived perovskite film. The results indicate that a high‐performance PSC can be achieved by combining a weak Lewis base with a well‐established solvent engineering process. [ABSTRACT FROM AUTHOR]

In quasi-solid electrolytes loaded with nanoparticles such as silica and titania, the solvent of the electrolyte has a key role in the separation of ionic species and their adsorption on the surface of nanoparticle. The present article demonstrates the effect of different solvents on the ionic adsorption and its impact on the photoelectrochemical characteristics of dye sensitized solar cells (DSSCs). Ionic adsorption behaviour has been studied by zeta potential measurements and analysis of carbon to nitrogen (C/N) ratio. It has been found out that effective cationic adsorption occurs in 3-methoxypropionitrile (MPN) as solvent in electrolyte, whereas poor adsorption occurs in N-methyl-2-pyrrolidone (NMP)-based electrolyte due to the higher donor number of the latter which results in effective interaction of solvent and nanopowder. Performance of DSSC fabricated with MPN-based solvent in electrolyte was superior to others in both liquid and quasi-solid electrolytes. [ABSTRACT FROM AUTHOR]

Among the "beyond Li-ion" battery chemistries, nonaqueous Li-O2 batteries have the highest theoretical specific energy and, as a result, have attracted significant research attention over the past decade. A critical scientific challenge facing nonaqueous Li-O2 batteries is the electronically insulating nature of the primary discharge product, lithium peroxide, which passivates the battery cathode as it is formed, leading to low ultimate cell capacities. Recently, strategies to enhance solubility to circumvent this issue have been reported, but rely upon electrolyte formulations that further decrease the overall electrochemical stability of the system, thereby deleteriously affecting battery rechargeability. In this study, we report that a significant enhancement (greater than fourfold) in Li-O2 cell capacity is possible by appropriately selecting the salt anion in the electrolyte solution. Using (7)Li NMR and modeling, we confirm that this improvement is a result of enhanced Li(+) stability in solution, which, in turn, induces solubility of the intermediate to Li2O2 formation. Using this strategy, the challenging task of identifying an electrolyte solvent that possesses the anticorrelated properties of high intermediate solubility and solvent stability is alleviated, potentially providing a pathway to develop an electrolyte that affords both high capacity and rechargeability. We believe the model and strategy presented here will be generally useful to enhance Coulombic efficiency in many electrochemical systems (e.g., Li-S batteries) where improving intermediate stability in solution could induce desired mechanisms of product formation.

Abstract Solvent engineering by Lewis‐base solvent and anti‐solvent is well known for forming uniform and stable perovskite thin films. The perovskite phase crystallizes from an intermediate Lewis‐adduct upon annealing‐induced crystallization. Herein, it is explored the effects of trimethyl phosphate (TMP), as a novel aprotic Lewis‐base solvent with a low donor number for the perovskite film formation and photovoltaic characteristics of perovskite solar cells (PSCs). As compared to dimethylsulfoxide (DMSO) or dimethylformamide (DMF), the usage of TMP directly crystallizes the perovskite phase, i.e., reduces the intermediate phase to a negligible degree, right after the spin‐coating, owing to the high miscibility of TMP with the anti‐solvent and weak bonding in the Lewis adduct. Interestingly, the PSCs based on methylammonium lead iodide (MAPbI3) derived from TMP/DMF‐mixed solvent exhibit a higher average power conversion efficiency of 19.68% (the best: 20.02%) with a smaller hysteresis in the current‐voltage curve, compared to the PSCs that are fabricated using DMSO/DMF‐mixed (19.14%) or DMF‐only (18.55%) solvents. The superior photovoltaic properties are attributed to the lower defect density of the TMP/DMF‐derived perovskite film. The results indicate that a high‐performance PSC can be achieved by combining a weak Lewis base with a well‐established solvent engineering process.

High donor number (DN) solvents in Li—O2 batteries that dissolve superoxide intermediates in lithium peroxide (Li2O2) formation facilitate high capacities at high rates and avoid early cell death. However, their beneficial characteristics also result in an instability towards highly reactive superoxide intermediates. Furthermore, Li—O2 batteries would deliver a superior energy density, but the multiphase electrochemical reactions are difficult to achieve when operating with only solid catalysts. Herein we demonstrate that vanadium(III) acetylacetonate (V(acac)3) is an efficient soluble catalyst that can address these problems. During discharge, V(acac)3 integrates with the superoxide intermediate, accelerating O2 reduction kinetics and reducing side reactions. During charge, V(acac)3 acts as a redox mediator that permits efficient oxidation of Li2O2. The cells with V(acac)3 exhibit low overpotential, high rate performance, and considerable cycle stability. [ABSTRACT FROM AUTHOR]

• The DN value of solvent has effect on PPy's preparation. • The lower the DN value, the less structural defects of PPy. • The lower the DN value, the higher conductivity of PPy. • PPy prepared in nitromethane solutions own the best corrosion protection performances. To clarify the effect of solvents with different donor number (DN) on the preparation and corrosion protection ability of polypyrrole (PPy) films, PPy were firstly synthesized in water or acetonitrile or nitromethane solutions containing NaClO 4 + pyrrole by a potentiostatic method. The corrosion protection performances of these films with stainless steel as a substrate were investigated by open circuit potential, potentiodynamic polarization and electrochemical impedance spectroscopy in 1 M H 2 SO 4. Results indicated that all PPy films showed spherical structure in scanning electron microscopy photograph and corrosion protection ability. Particularly, PPy prepared in nitromethane solutions performed the best due to the lowest DN value. Nitromethane had the weakest interaction with the intermediates of pyrrole polymerization which results in the smallest particles, the most compact accumulation, the highest conductivity and the longest conjugated chain. [ABSTRACT FROM AUTHOR]

The two-photon absorption (TPA) properties of a series of D-A-D type chromophores containing tetraphenylethylene (TPE) and triphenylamine moieties have been investigated employing the density functional response theory in combination with the polarisable continuum model. Special emphases are placed on the effects of the strength, position and number of donors on TPA. Our calculations demonstrate that the TPA intensity enhances with the increase of the electron-donating ability of the substituents on the triphenylamine unit, which is consistent with experimental observations. It is shown that the position of donors has an important effect on TPA. The donor on the side position of TPE unit decreases the TPA cross section, thereby more donors could not necessarily produce stronger TPA. The cis-trans isomerism effect is also explored and it is found that all the cis structures have lower TPA intensities than those of corresponding trans forms. By considering a different number of donors on TPE and triphenylamine unit respectively, it is interesting to find that the structure with one terminal donor on TPE and two donors on triphenylamine unit has the largest TPA cross section. The few-state model and the natural bond orbital charge analysis are used to explore the reason behind it. [ABSTRACT FROM AUTHOR]

The lithium-sulfur (Li-S) battery is one of the promising energy storage alternatives because of its high theoretical capacity and energy density. Factors governing the stability of polysulfide intermediates in Li-S batteries are complex and are strongly affected by the solvent used. Herein, the polysulfide reduction and the bond cleavage reactions are calculated in different solvent environments by the density functional theory (DFT) methods. We investigate the relationship between the donor numbers (DN) as well as the dielectric constants (ε) of the solvent system and the relative stability of different polysulfide intermediates. Our results show that the polysulfide reduction mechanism is dominated by its tendency to form the ion-pair with Li+ in different organic solvents.

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.

The low reversibility of Li deposition/stripping in conventional carbonate electrolytes hinders the development of lithium metal batteries. Herein, we proposed a combination of solvents with a moderate donor number (DN) and LiNO 3 as the sole salt, which has rarely been attempted due to its low solubility or dissociation degree in common solvents. It is found that the DN value of solvents is highly correlated to the reversibility of Li deposition behavior when LiNO 3 is applied as the sole salt. The combination of LiNO 3 and solvents with moderate DN behaves like a quasi-concentrated electrolyte even at a common or moderate concentration, while neither the solvents with poor solubility and low dissociation for LiNO 3 (which usually corresponds to a low DN) nor the solvents with high dissociation for LiNO 3 (which usually corresponds to an overly high DN) can achieve a high reversibility for low conductivity or excessive solvent decomposition. As a result, a Coulombic efficiency as high as 99.6% for Li deposition/stripping is achieved with the optimized combination. We believe this work will give a better understanding of the role of anions and solvents in the regulation of the solvation structure, and DN can be utilized as an important guideline to sieve suitable solvents for LiNO 3 as the main salt to exhibit intriguing properties beyond traditional cognition.

Abstract Electrochemical oxidation of N , N , N ′, N ′-tetramethyl-1,4-phenylenediamine (TMPD) to its cation radical (TMPD •+) and dication (TMPD ++ ) in various nonaqueous solvents was studied using the cyclic voltammetry technique on a glassy carbon electrode. The variation of the half-wave potentials (E 1/2) with the physical properties of the solvents was interpreted using multi-parametric correlation. It is shown that polarity-polarizability index, viscosity and longitudinal relaxation of solvents play an undeniable role in the E 1/2 value. The electron transfer rate constants were simulated and analyzed using the MLR regression method to separate the effect of longitudinal relaxation time from other effective parameters according to the Marcus theory. Finally, a new correlation method was developed which involve solvent's Pekar factor, longitudinal and Debye relaxation time, viscosity and relative permittivity. The computational method was used for calculating the standard of the Gibbs free energy of solvation and oxidation process. Graphical abstract The effects of different solvents on the electrochemical oxidation of N,N,N′,N′ -tetramethyl-1,4-phenylenediamine (TMPD) was studied experimentally using the cyclic voltammetry and theoretically according to the Marcus theory. Image 1 Highlights • Solvent effects on electrooxidation of N,N,N′,N′ -tetramethyl-1,4-phenylenediamine. • Solvent physical properties on E 1/2 of N,N,N′,N′ -tetramethyl-1,4-phenylenediamine. • The role of longitudinal relaxation time on electron transfer rate constant. • Developing a new correlation method between solvent's Pekar factor, τ L , τ D , η and ε r. • Calculating the standard Gibbs free energy of solvation and oxidation process [ABSTRACT FROM AUTHOR]

We have reported oligo( p-phenylene)s (OPPs) with an OH group located at one end, namely, OPP( n)-OHs (where n is the number of benzene rings). The OPPs exhibited significant solvatochromism; the deprotonation of the OH groups of OPP( n)-OHs, when treated with NaH, caused a bathochromic shift of absorption maxima (λmax) that increased with the donor numbers (DNs) of the solvents. We assumed that the solvatochromism exhibited by OPP( n)-ONa was attributed to an intramolecular charge shift from the sodium phenoxy group(s) to the adjacent rings. In this study, to investigate the assumption, hydroxyoligophenylenes ( R-OPP( n)-OH) with an electron-donating dimethylamino group ( n = 3, R = NMe2), an electron-accepting nitro group ( n = 3, R = NO2), and a π-deficient pyridine ring ( n = 2, R = Py) were synthesized by the Suzuki coupling reaction. The deprotonation of the OH group of by treatment with NaH caused a bathochromic shift (Δλ) of λmax of R-OPP( m)-ONa. The Δλ of the deprotonated species increased with the DNs of the solvents. The emission peak positions of R-OPP( m)-ONa depended on the DNs of the solvents; therefore, the emission color could be tuned by changing the solvent. R-OPP( m)-OH received an electrochemical oxidation of the OH group and OPP unit. The data related to the remarkable solvatochromic behavior of R-OPP( n)-ONa will be useful information for the development of new luminescent materials. [ABSTRACT FROM AUTHOR]

Nano-composite polymer gel electrolytes were synthesized by using polyethylene oxide (PEO), ammonium tetrafluoroborate (NHBF), fumed silica (SiO), dimethylacetamide (DMA), ethylene carbonate (EC), and propylene carbonate (PC) and characterized by conductivity studies. The effect of donor number of solvent on ionic conductivity of polymer gel electrolytes has been studied. The mechanical strength of the gel electrolytes has been increased with the addition of nano-sized fumed silica along with an enhancement in conductivity. Maximum room temperature ionic conductivity of 2.63 × 10 and 2.92 × 10 S/cm has been observed for nano-composite gel electrolytes containing 0.1 and 0.5 wt% SiO in DMA+1 M NHBF+10 wt% PEO, respectively. Nano-composite polymer gel electrolytes having DMA have been found to be thermally and electrically stable over 0 to 90 °C temperature range. Also, the change in conductivity with the passage of time is very small, which may be desirable to make applicable for various smart devices. [ABSTRACT FROM AUTHOR]

Proton conducting nano-composite polymer gel electrolytes containing Polymethylmethacrylate (PMMA), Benzoic Acid (BA), Ethylene Carbonate (EC), Propylene Carbonate (PC), Dimethylformamide (DMF), and nano-sized Alumina (Al2 O3) have been prepared and characterized by electrochemical impedance spectroscopy. The effect of donor number of solvent used and nano-sized alumina on ionic conductivity of gel electrolytes has been studied. Maximum room temperature conductivity of 1.83 x 10-4 S/cm for nano-composite polymer gel electrolytes at 7 wt% concentration of Al2 O3 along with good mechanical stability has been obtained. Two conductivity maxima have been observed with the 2 3 addition of nano-sized alumina. First maximum at low Al2 O3 concentration has been explained due to the enhanced dissociation of undissociated acid/ion aggregates, whereas second maximum at high concentrations is due to formation of a high conducting interfacial layer between nano-particles and polymer gel electrolytes. The variation of conductivity with temperature and time has also been studied to check the stability of electrolytes. The change in conductivity with temperature is very small, which is desirable for their use in various electrochemical devices. [ABSTRACT FROM AUTHOR]

• Lewis basicity is an essential property of molecules used as electrolytes and additives. • The Gutmann Donor Number of alkyl carbonates shows shortcomings. • The enthalpy of adduct formation with boron trifluoride is a reliable measure of Lewis basicity. • Experimental data and ab initio calculation can be used as an alternative to Donor Number. Alkyl carbonates are essential components in the manufacture of lithium-ion batteries, as electrolytes or additives. The Lewis basicity of alkyl carbonates and other carbonyl compounds used in electrochemistry are often characterized by their Donor Number (DN). Assessment of the literature DN values displays great discrepancies. This is attributed in part to experimental errors, but mostly to inconsistent methods of determination. An alternative Lewis basicity scale is proposed, based on the enthalpy of adduct formation of a Lewis base with BF 3 in dichloromethane solvent -Δ H (BF 3). Experimental data are well reproduced by a modified ab initio G4 method and a mixed cluster-continuum approach of solvation. These calculations permit a confident estimation of previously not measured -Δ H (BF 3) values. The combination of a large set of experimental data and of calculations provides a consistent source of Lewis basicity of molecules used in electrochemistry and related fields. [ABSTRACT FROM AUTHOR]

Transforming CO 2 into valuable chemicals is an inevitable trend in our current society. Among the viable end-uses of CO 2 , fixing CO 2 as carbon or carbonates via Li-CO 2 chemistry could be an efficient approach, and promising achievements have been obtained in catalyst design in the past. Even so, the critical role of anions/solvents in the formation of a robust solid electrolyte interphase (SEI) layer on cathodes and the solvation structure have never been investigated. Herein, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in two common solvents with various donor numbers (DN) have been introduced as ideal examples. The results indicate that the cells in dimethyl sulfoxide (DMSO)-based electrolytes with high DN possess a low proportion of solvent-separated ion pairs and contact ion pairs in electrolyte configuration, which are responsible for fast ion diffusion, high ionic conductivity, and small polarization. The 3 M DMSO cell delivered the lowest polarization of 1.3 V compared to all the tetraethylene glycol dimethyl ether (TEGDME)-based cells (about 1.7 V). In addition, the coordination of the O in the TFSI - anion to the central solvated Li + ion was located at around 2 Å in the concentrated DMSO-based electrolytes, indicating that TFSI - anions could access the primary solvation sheath to form an LiF-rich SEI layer. This deeper understanding of the electrolyte solvent property for SEI formation and buried interface side reactions provides beneficial clues for future Li-CO 2 battery development and electrolyte design.

Effect of the solvent nature on the kinetics of photoreduction of 3,6-di- tert-butyl-1,2-benzoquinone and its six derivatives in the presence of N, N-dimethylaniline and 4-( N, N-dimethylamino)benzaldehyde has been investigated. It has been found that for the о-quinone-amine pair, for which the free energy change of electron transfer is Δ G > +0.11 eV, the rate constant of о-quinone photoreduction k decreases proportionally to the increase in the acceptor number of the solvent. For the о-quinone-amine pair with Δ G < +0.11 eV, the k value decreases proportionally to the increase in the donor number of the solvent. It has been established that the enhancement of the electron-acceptor properties of the solvent leads to the emergence of kinetic isotope effect for the reactant pairs of 3,6-di- tert-butyl-1,2-benzoquinone and 4,5-dimethoxy-3,6-di- tert-butyl-1,2-benzoquinone with N, N-di-methylaniline (Δ G = +0.11 and +0.22 eV, respectively). [ABSTRACT FROM AUTHOR]

Among the "beyond Li-ion" battery chemistries, nonaqueous Li-O2 batteries have the highest theoretical specific energy and, as a result, have attracted significant research attention over the past decade. A critical scientific challenge facing nonaqueous Li-O2 batteries is the electronically insulating nature of the primary discharge product, lithium peroxide, which passivates the battery cathode as it is formed, leading to low ultimate cell capacities. Recently, strategies to enhance solubility to circumvent this issue have been reported, but rely upon electrolyte formulations that further decrease the overall electrochemical stability of the system, thereby deleteriously affecting battery rechargeability. In this study, we report that a significant enhancement (greater than fourfold) in Li-O2 cell capacity is possible by appropriately selecting the salt anion in the electrolyte solution. Using 7Li NMR and modeling, we confirm that this improvement is a result of enhanced Li+ stability in solution, which, in turn, induces solubility of the intermediate to Li2O2 formation. Using this strategy, the challenging task of identifying an electrolyte solvent that possesses the anticorrelated properties of high intermediate solubility and solvent stability is alleviated, potentially providing a pathway to develop an electrolyte that affords both high capacity and rechargeability. We believe the model and strategy presented here will be generally useful to enhance Coulombic efficiency in many electrochemical systems (e.g., Li-S batteries) where improving intermediate stability in solution could induce desired mechanisms of product formation. [ABSTRACT FROM AUTHOR]