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Electrolyte additives with multiple functions enable the interfacial engineering of Li‐metal batteries (LMBs). Owing to their unique reduction behavior, additives exhibit a high potential for electrode surface modification that increases the reversibility of Li‐metal anodes by enabling the development of a hierarchical solid electrolyte interphase (SEI). This study confirms that an adequately designed SEI facilitates the homogeneous supply of Li+, nonlocalized Li deposition, and low electrolyte degradation in LMBs while enduring the volume fluctuation of Li‐metal anodes on cycling. An in‐depth analysis of interfacial engineering mechanisms reveals that multilayered SEI structures comprising mechanically robust LiF‐rich species, electron‐rich P–O species, and elastic polymeric species enabled the stable charge and discharge of LMBs. The polymeric outer SEI layer in the as‐fabricated multilayered SEI could accommodate the volume fluctuation of Li‐metal anodes, significantly enhancing the cycling stability Li||LiNi0.8Co0.1Mn0.1O2 full cells with an electrolyte amount of 3.6 g Ah−1 and an areal capacity of 3.2 mAh cm−2. Therefore, this study confirms the ability of interfacial layers formed by electrolyte additives and fluorinated solvents to advance the performance of LMBs and can open new frontiers in the fabrication of high‐performance LMBs through electrolyte‐formulation engineering. [ABSTRACT FROM AUTHOR]

Currently, commercial lithium (Li) ion batteries (LIBs) do not meet the energy density (>350 W h kg−1) required for vehicle electrification; therefore, alternative materials are required. Lithium metal batteries (LMBs) are promising secondary battery candidates for next-generation, eco-friendly energy conversion given their high theoretical gravimetric capacities (3862 mA h g−1). However, strong reduction by Li metal electrochemically decomposes the electrolytes, reducing battery performance, safety, and stability. To overcome these potential issues, the LMB electrolyte must be very resistant to oxidation. Here, we used leakage current tests to investigate the oxidation stability of organic electrolytes for LMBs. We performed quantum and molecular dynamics simulations to clarify the effects of gel polymers added to the electrolyte. We focused on changes in the behaviors of free organic molecules after the addition of polymers, and the highest/lowest occupied molecular orbital energy levels of various molecular configurations. The leakage current tests revealed improvements to the oxidation stability of an organic-based electrolyte. In addition, polymer addition resulted in a decrease in free organic molecule levels, improving the oxidation stability of the entire system as revealed by the highest occupied molecular orbital energy values of the various molecular configurations. [ABSTRACT FROM AUTHOR]

Ionic liquids (ILs) with aproticheterocyclic anions (AHA) areattractive candidates for CO2capture technologies. Inthis study, a series of AHA ILs with 1-ethyl-3-methylimidazolium ([emim]+) cations were synthesized, and their physical properties(density, viscosity, and ionic conductivity) were measured. In addition,CO2solubility in each IL was determined at room temperatureusing a volumetric method at pressures between 0 and 1 bar. The AHAsare basic anions that are capable of reacting stoichiometrically withCO2to form carbamate species. An interesting CO2uptake isotherm behavior was observed, and this may be attributedto a parallel, equilibrium proton exchange process between the imidazoliumcation and the basic AHA in the presence of CO2, followedby the formation of “transient” carbene species thatreact rapidly with CO2. The presence of the imidazolium-carboxylatespecies and carbamate anion species was verified using 1H and 13C NMR spectroscopy. While the reaction betweenCO2and the proposed transient carbene resulted in cation-CO2binding that is stronger than the anion-CO2reaction,the reactions of the imidazolium AHA ILs were fully reversible uponregeneration at 80 °C with nitrogen purging. The presence ofwater decreased the CO2uptake due to the inhibiting effectof the neutral species (protonated form of AHA) that is formed. [ABSTRACT FROM AUTHOR]

Ionic liquids (ILs) with aproticheterocyclic anions, or AHAs,can bind CO2with reaction enthalpies that are suitablefor gas separations and without suffering large viscosity increases.In the present work, we have synthesized ILs bearing an alkyl-phosphoniumcation with indazolide, imidazolide, pyrrolide, pyrazolide and triazolide-basedanions that span a wide range of predicted reaction enthalpies withCO2. Each AHA-based IL was characterized by NMR spectroscopyand their physical properties (viscosity, glass transition, and thermaldecomposition temperature) determined. In addition, the influenceof substituent groups on the reaction enthalpy was investigated bymeasuring the CO2solubility in each IL at pressures between0 and 1 bar at 22 °C using a volumetric method.The isotherm-derived enthalpies range between −37 and −54kJ mol–1of CO2, and these values arein good agreement with computed enthalpies of gas-phase IL-CO2reaction products from molecular electronic structure calculations.The AHA ILs show no substantial increase in viscosity when fully saturatedwith CO2at 1 bar. Phase splitting and compositional analysisof one of the IL/H2O and IL/H2O/CO2systems conclude that protonation of the 2-cyanopyrrolide anionis improbable, and this result was confirmed by the equimolar CO2absorption in the presence of water. Taking advantage ofthe tunable binding energy and absence of viscosity increase afterthe reaction with CO2, AHA ILs are promising candidatesfor efficient and environmental-friendly absorbents in postcombustionCO2capture. [ABSTRACT FROM AUTHOR]

The high theoretical energy densities of lithium-air batteries (LAB) make this technology an attractive energy storage system for future mobility applications. Li 2 O 2 growth process on the cathode relies on the surrounding chemical environment of electrolytes. Low conductivity and strong reactivity of Li 2 O 2 discharge products can cause overpotential and induce side reactions in LABs, respectively, eventually leading to poor cyclability. The capacity and reversibility of LABs are highly susceptible to the morphology of the Li 2 O 2 discharge products. Here, we identify for the first time that a seed layer formed by the combination of a cathode and an electrolyte determines the morphology of Li 2 O 2 discharge products. This seed layer led to its high reversibility with a large areal capacity (up to 10 mAh/cm 2 ). Excellent OER (oxygen evolution reaction) was achieved by the formation of a favorable interface between the carbon electrode and electrolyte, minimizing the decomposition of the electrolyte. These remarkable improvements in LAB performance demonstrate critical progress toward advancing LAB into practical uses, which would exploit good reversibility of LABs in pouch-type cell arrangements with 1.34 Ah.

We synthesized ionic liquids (ILs) comprising an alkylphosphonium cation paired with phenolate, 4-nitrophenolate, and 4-methoxyphenolate anions that span a wide range of predicted reaction enthalpies with CO2. Each phenolate-based IL was characterized by spectroscopic techniques, and their physical properties (viscosity, conductivity, and CO2 solubility) were determined. We use the computational quantum chemical approach paired with experimental results to reveal the reaction mechanism of CO2 with phenolate ILs. Model chemistry shows that the oxygen atom of phenolate associates strongly with phosphonium cations and is able to deprotonate the cation to form an ylide with an affordable activation barrier. The ATR-FTIR and (31)P NMR spectra indicate that the phosphonium ylide formation and its reaction with CO2 are predominantly responsible for the observed CO2 uptake rather than direct anion-CO2 interaction.