Maximum Electrical Conductivity of Associated Lithium Salts in Solvents for Lithium-Air Batteries

The choice of optimal electrolytes is crucial for improving the electrochemical performance of a lithium air battery because it determines the morphology of the discharge products in the cathode and the conductivity of the electrolyte. We have critically analyzed an important aspect related to the behavior of highly associated electrolytes, as those used in lithium-air batteries: the prediction of the concentration of maximum conductivity. Lithium triflate and lithium bis(tri-fluoromethyl sulfonyl)imide in glymes of low dielectric constant (1,2-di-methoxyethane and bis(2-methoxy-ethyl)ether) were used as a model of electrolytes exhibiting strong ionic clustering. The viscosity and lithium transference number of all the electrolytes were measured, and it was found that the correlation between the concentration of maximum conductivity and coefficient that describes the high-order dependence of the electrolyte viscosity with the concentration is no longer valid in these electrolytes because of the failure of Walden´s rule, although a qualitative correlation with the salts´ association constant was observed.Fil: Horwitz, Gabriela. Comisión Nacional de Energía Atómica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología; ArgentinaFil: Rodríguez, Cristian. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad de Microanálisis y Métodos Físicos en Química Orgánica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Unidad de Microanálisis y Métodos Físicos en Química Orgánica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Factorovich, Matias Hector. Comisión Nacional de Energía Atómica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología; ArgentinaFil: Corti, Horacio Roberto. Comisión Nacional de Energía Atómica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentin

Electrochemical stability of glyme-based electrolytes for Li-O2batteries studied by: In situ infrared spectroscopy

In situ subtractively normalized Fourier transform infrared spectroscopy (SNIFTIRS) experiments were performed simultaneously with electrochemical experiments relevant to Li–air battery operation on gold electrodes in two glyme-based electrolytes: diglyme (DG) and tetraglyme (TEGDME), tested under different operational conditions. The results show that TEGDME is intrinsically unstable and decomposes at potentials between 3.6 and 3.9 V vs. Li+/Li even in the absence of oxygen and lithium ions, while DG shows a better stability, and only decomposes at 4.0 V vs. Li+/Li in the presence of oxygen. The addition of water to the DG based electrolyte exacerbates its decomposition, probably due to the promotion of singlet oxygen formation.Fil: Horwitz, Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Calvo, Ernesto Julio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Méndez de Leo, Lucila Paula. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: de la Llave, Ezequiel Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentin

Perceived Diet Quality, Eating Behaviour, and Lifestyle Changes in a Mexican Population with Internet Access during Confinement for the COVID-19 Pandemic: ESCAN-COVID19Mx Survey

Perceived changes in diet quality, emotional eating, physical activity, and lifestyle were evaluated in a group of Mexican adults before and during COVID-19 confinement. In this study, 8289 adults answered an online questionnaire between April and May 2020. Data about sociodemographic characteristics, self-reported weight and height, diet quality, emotional eating, physical activity, and lifestyle changes were collected. Before and after confinement, differences by sociodemographic characteristics were assessed with Wilcoxon, Anova, and linear regression analyses. Most participants were women (80%) between 18 and 38 years old (70%), with a low degree of marginalisation (82.8%) and a high educational level (84.2%); 53.1% had a normal weight and 31.4% were overweight. Half (46.8%) of the participants perceived a change in the quality of their diet. The Diet Quality Index (DQI) was higher during confinement (it improved by 3 points) in all groups, regardless of education level, marginalisation level, or place of residence (p 0.001). Lifestyle changes were present among some of the participants, 6.1% stopped smoking, 12.1% stopped consuming alcohol, 53.3% sleep later, 9% became more sedentary, and increased their screen (43%) as well as sitting and lying down time (81.6%). Mexicans with Internet access staying at home during COVID-19 confinement perceived positive changes in the quality of their diet, smoking, and alcohol consumption, but negative changes in the level of physical activity and sleep quality. These results emphasise the relevance of encouraging healthy lifestyle behaviours during and after times of crisis to prevent the risk of complications due to infectious and chronic diseases

Volumetric and viscosity properties of water-in-salt lithium electrolytes: A comparison with ionic liquids and hydrated molten salts

The density and viscosity of LiTf, LiTFSI and LiTFSI + LiTf (mole ratio 3:1) aqueous solutions have been measured at temperatures between 25 °C and 55 °C, over a wide range of concentrations covering the Water-in-Salt (WiS) region, where no free water is present in the system. As it was observed in mixtures of ionic liquids with water and mixtures of melted salt hydrates, the molar volumes of these WiS electrolytes are linear functions of the salt mole fraction. We propose a new procedure to calculate the intrinsic volume of the salts in the WiS solutions, corresponding to the volume of the hypothetical supercooled pure salts. The contributions of electrostriction and conformational changes of the anion to the partial molar volume of the WiS are discussed. The presence of Li+ ions in the salts free of water (supercooled salts) produces a large contraction of the Tf− and TFSI− volumes as compared with ionic liquids containing the same anions in contact with bulky cations. In terms of the apparent partial molar volume of water we could identify a dilute regime (x ≤ 0.1) where the volumetric properties are dominated by the water electrostriction, and a WiS regime (x > 0.1), without free-water, where the molar volume is determined by the volumes of the hydrated Li+ ion and the corresponding dehydrated anion, compatible with a proposed WiS structure formed by a percolating network of anions embedded by Li(H2O)n+ cations. The excess volume of the ternary WiS (LiTf + LiTFSI) is very small at all temperatures and concentrations, while the excess viscosity is positive and small, but increases near the solubility limit. The viscosity of the WiS electrolytes exhibit a normal Arrhenius dependence, but simple extrapolation to the glass transition temperature indicates that the WiS electrolytes behave as fragile fluids.Fil: Horwitz, Gabriela. Comisión Nacional de Energía Atómica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología; ArgentinaFil: Steinberg, Paula Yael. Comisión Nacional de Energía Atómica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Corti, Horacio Roberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina. Comisión Nacional de Energía Atómica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología; Argentin

Lithium Air Batteries – Tracking Function and Failure

The lithium-air battery (LAB) is arguably the battery with the highest energy density, but also a battery with significant challenges to be overcome before it can be used commercially in practical devices. Here, we discuss experimental approaches developed by some of the authors to understand the function and failure of lithium-oxygen batteries. For example, experiments in which nuclear magnetic resonance (NMR) spectroscopy was used to quantify dissolved oxygen concentrations and diffusivity are described. 17O MAS NMR spectra of electrodes extracted from batteries at different states of charge (SOC) allowed the electrolyte decomposition products at each stage to be determined. For instance, the formation of Li2CO3 and LiOH in a DME solvent and their subsequent removal on charging was followed. Redox mediators have been used to chemically reduce oxygen or to chemically oxidise Li2O2 in order to prevent electrode clogging by insulating compounds, which leads to lower capacities and rapid degradation; the studies of these mediators representing an area where NMR and electron paramagnetic resonance (EPR) studies could play a role in unravelling reaction mechanisms. Finally, recently developed coupled in-situ NMR and electrochemical impedance spectroscopy (EIS) are used to characterise the charge transport mechanism in lithium symmetric cells and to distinguish between electronic and ionic transport, demonstrating the formation of transient (soft) shorts in lithium-oxygen common electrolytes. More stable solid electrolyte interphases are formed under oxygen atmosphere, which help stabilises the lithium anode on cycling.JE and CPG acknowledge support from a Royal Society Research Professorship for CPG (grant no. RP\R1\180147). JE and CPG also acknowledge support from an ERC Advanced Investigator Grant for CPG (grant no. EC H2020 ERC 835073). GH acknowledges support from a Faraday Institution grant (grant no. FIRG060). JBF gratefully acknowledge funding by the Faraday Institute through the LiSTAR (FIRG014, FIRG058). SM gratefully acknowledge funding by the Faraday Institute through the NEXGENNa (FIRG018)

Mobility-viscosity decoupling and cation transport in water-in-salt lithium electrolytes

Two super-concentrated aqueous electrolyes, or water-in-salt electrolytes, comprising the lithium trifluoromethanesulfonate (LiTf-H2O) binary system, and the ternary system with bis(trifluoromethanesulfonyl)-imide (LiTFSI-LiTf-H2O), were analyzed in relation to their conductivity, viscosity, diffusion of all the species and cationic transport number. The conductivity-viscosity and the ionic diffusion-viscosity decoupling were analyzed by means of the Walden law and the Stokes-Einstein relationship, respectively. The results, including those already reported for LiTFSI-H2O, reveal the existence of a significant decoupling of the Li+ mobility from the solution viscosity, while the corresponding anions follow the classical hydrodynamic behaviour. The Li+ apparent transport number, derived from the self-diffusion coefficients measured by NMR, increases with concentration, due to the decoupling. These facts strongly support the formation of two types of nano-domains in the superconcentrated salt solutions with different mobility characteristics: a region formed by a net of anions with restricted mobility, percolated by clusters of reduced local viscosity that boost the mobility of Li+ ions. Finally, the difference between the experimental conductivity and that calculated using the Nernst-Einstein equation was rationalized in terms of the velocity correlation and resistance coefficients calculated using the measured transport coefficients.Fil: Horwitz, Gabriela. Comisión Nacional de Energía Atómica. Gerencia de Área Investigaciones y Aplicaciones No Nucleares. Gerencia Física (CAC). Departamento de Física de la Materia Condensada; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Rodriguez, Cristian Ramon. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad de Microanálisis y Métodos Físicos en Química Orgánica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Unidad de Microanálisis y Métodos Físicos en Química Orgánica; ArgentinaFil: Steinberg, Paula Yael. Comisión Nacional de Energía Atómica. Gerencia del Área de Seguridad Nuclear y Ambiente. Gerencia de Química (CAC); Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Burton, Gerardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad de Microanálisis y Métodos Físicos en Química Orgánica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Unidad de Microanálisis y Métodos Físicos en Química Orgánica; ArgentinaFil: Corti, Horacio Roberto. Comisión Nacional de Energía Atómica. Gerencia de Área Investigaciones y Aplicaciones No Nucleares. Gerencia Física (CAC). Departamento de Física de la Materia Condensada; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentin

Spiers Memorial Lecture: Lithium air batteries - tracking function and failure.

Acknowledgements: JE and CPG acknowledge support from a Royal Society Research Professorship for CPG (grant no. RP\R1\180147). JE and CPG also acknowledge support from an ERC Advanced Investigator Grant for CPG (grant no. EC H2020 ERC 835073). GH acknowledges support from a Faraday Institution grant (grant no. FIRG060). JBF gratefully acknowledges funding by the Faraday Institute through LiSTAR (FIRG014, FIRG058). SM gratefully acknowledges funding by the Faraday Institute through NEXGENNa (FIRG018). LB acknowledges support from the EPSRC through the NanoDTC (grant no. EP/S022953/1).The lithium-air battery (LAB) is arguably the battery with the highest energy density, but also a battery with significant challenges to be overcome before it can be used commercially in practical devices. Here, we discuss experimental approaches developed by some of the authors to understand the function and failure of lithium-oxygen batteries. For example, experiments in which nuclear magnetic resonance (NMR) spectroscopy was used to quantify dissolved oxygen concentrations and diffusivity are described. 17O magic angle spinning (MAS) NMR spectra of electrodes extracted from batteries at different states of charge (SOC) allowed the electrolyte decomposition products at each stage to be determined. For instance, the formation of Li2CO3 and LiOH in a dimethoxyethane (DME) solvent and their subsequent removal on charging was followed. Redox mediators have been used to chemically reduce oxygen or to chemically oxidise Li2O2 in order to prevent electrode clogging by insulating compounds, which leads to lower capacities and rapid degradation; the studies of these mediators represent an area where NMR and electron paramagnetic resonance (EPR) studies could play a role in unravelling reaction mechanisms. Finally, recently developed coupled in situ NMR and electrochemical impedance spectroscopy (EIS) are used to characterise the charge transport mechanism in lithium symmetric cells and to distinguish between electronic and ionic transport, demonstrating the formation of transient (soft) shorts in common lithium-oxygen electrolytes. More stable solid electrolyte interphases are formed under an oxygen atmosphere, which helps stabilise the lithium anode on cycling.JE and CPG acknowledge support from a Royal Society Research Professorship for CPG (grant no. RP\R1\180147). JE and CPG also acknowledge support from an ERC Advanced Investigator Grant for CPG (grant no. EC H2020 ERC 835073). GH acknowledges support from a Faraday Institution grant (grant no. FIRG060). JBF gratefully acknowledge funding by the Faraday Institute through the LiSTAR (FIRG014, FIRG058). SM gratefully acknowledge funding by the Faraday Institute through the NEXGENNa (FIRG018)

The nanostructure of water-in-salt electrolytes revisited: effect of the anion size

The increasing interest in developing safe and sustainable energy storage systems has led to the rapid rise in attention to superconcentrated electrolytes, commonly called water-in-salt (WiS). Several works indicate that the transport properties of these liquid electrolytes are related to the presence of nanodomains, but a detailed characterization of such structure is missing. Here, the structural nano-heterogeneity of lithium WiS electrolytes, comprising lithium trifluoromethanesulfonate (LiTf) and bis(trifluoromethanesulfonyl)imide (LiTFSI) solutions as a function of concentration and temperature, was assessed by resorting to the analysis of small-angle neutron scattering (SANS) patterns. Variations with the concentration of a correlation peak, rather temperature-independent, in a Q range around 3.5-5 nm-1 indicate that these electrolytes are composed of nanometric water-rich channels percolating a 3D dispersing anion-rich network, with differences between Tf and TFSI anions related to their distinct volumes and interactions. Furthermore, a common trend was found for both systems' morphology above a salt volume fraction of ∼0.5. These results imply that the determining factor in the formation of the nanostructure is the salt volume fraction (related to the anion size), rather than its molality. These findings may represent a paradigm shift for designing WiS electrolytes.Fil: Horwitz, Gabriela. Comisión Nacional de Energía Atómica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología; Argentina. Comisión Nacional de Energía Atómica. Gerencia de Área Investigaciones y Aplicaciones No Nucleares. Gerencia Física (CAC). Departamento de Física de la Materia Condensada; ArgentinaFil: Härk, Eneli. Helmholtz-Zentrum Berlin. Department for Electrochemical Energy Storage; AlemaniaFil: Steinberg, Paula Yael. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Seguridad Nuclear y Ambiente. Gerencia de Química (CAC); ArgentinaFil: Cavalcanti, Leide P.. ISIS Neutron and Muon Source. Rutherford Appleton Laboratory; Reino UnidoFil: Risse, Sebastian. Helmholtz-Zentrum Berlin. Department for Electrochemical Energy Storage; AlemaniaFil: Corti, Horacio Roberto. Comisión Nacional de Energía Atómica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina. Comisión Nacional de Energía Atómica. Gerencia de Área Investigaciones y Aplicaciones No Nucleares. Gerencia Física (CAC). Departamento de Física de la Materia Condensada; Argentin

Spiers Memorial Lecture: Lithium air batteries – tracking function and failure

Acknowledgements: JE and CPG acknowledge support from a Royal Society Research Professorship for CPG (grant no. RP\R1\180147). JE and CPG also acknowledge support from an ERC Advanced Investigator Grant for CPG (grant no. EC H2020 ERC 835073). GH acknowledges support from a Faraday Institution grant (grant no. FIRG060). JBF gratefully acknowledges funding by the Faraday Institute through LiSTAR (FIRG014, FIRG058). SM gratefully acknowledges funding by the Faraday Institute through NEXGENNa (FIRG018). LB acknowledges support from the EPSRC through the NanoDTC (grant no. EP/S022953/1).Here, we discuss experimental approaches developed by some of the authors to understand the function and failure of lithium–oxygen batteries.</jats:p