The lithium/sulfur battery is a promising electrochemical system that has a high theoretical capacity of 1675 mAh g–1, but its discharge mechanism is well-known to be a complex multistep process. As ...the active material dissolves during cycling, this discharge mechanism was investigated through the electrolyte characterization. Using high-performance liquid chromatography, UV–visible absorption, and electron spin resonance spectroscopies, we investigated the electrolyte composition at different discharge potentials in a TEGDME-based electrolyte. In this study, we propose a possible mechanism for sulfur reduction consisting of three steps. Long polysulfide chains are produced during the first reduction step (2.4–2.2 V vs Li+/Li), such as S8 2– and S6 2–, as evidenced by UV and HPLC data. The S3 •– radical can also be found in solution because of a disproportionation reaction. S4 2– is produced during the second reduction step (2.15–2.1 V vs Li+/Li), thus pointing out the gradual decrease of the polysulfide chain lengths. Finally, short polysulfide species, such as S3 2–, S2 2–, and S2–, are produced at the end of the reduction process, i.e., between 2.1 and 1.9 V vs Li+/Li. The precipitation of the poorly soluble and insulating short polysulfide compounds was evidenced, thus leading to the positive electrode passivation and explaining the early end of discharge.
► Liquid electrolyte composition for lithium/sulfur secondary batteries. ► Carbonate-based electrolytes prove not to be compatible with the sulfur electrode. ► Poor electrochemical performances ...related to low polysulfide solubility. ► Increase in the discharge capacity using ether solvents with high solvating ability such as PEGDME. ► Evidence of DIOX polymerization during cycling.
The lithium/sulfur (Li/S) battery is a promising electrochemical system that has a high theoretical capacity of 1675mAhg−1. However, the system suffers from several drawbacks: poor active material conductivity, active material dissolution, and use of the highly reactive lithium metal electrode. In this study, we investigated the electrolyte effects on electrochemical performances of the Li/S cell, by acting on the solvent composition. As conventional carbonate-based electrolytes turned out to be unusable in Li/S cells, alternative ether solvents had to be considered. Different kinds of solvent structures were investigated by changing the ether/alkyl moieties ratio to vary the lithium polysulfide solubility. This allowed to point out the importance of the solvent solvation ability on the discharge capacity. As the end of discharge is linked to the positive electrode passivation, an electrolyte having high solvation ability reduces the polysulfide precipitation and delays the positive electrode passivation.
In this Full Paper we show that the use of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as conducting salt in commercial lithium‐ion batteries is made possible by introducing fluorinated ...linear carbonates as electrolyte (co)solvents. Electrolyte compositions based on LiTFSI and fluorinated carbonates were characterized regarding their ionic conductivity and electrochemical stability towards oxidation and with respect to their ability to form a protective film of aluminum fluoride on the aluminum surface. Moreover, the investigation of the electrochemical performance of standard lithium‐ion anodes (graphite) and cathodes (LiNi1/3Mn1/3Co1/3O2, NMC) in half‐cell configuration showed stable cycle life and good rate capability. Finally, an NMC/graphite full‐cell confirmed the suitability of such electrolyte compositions for practical lithium‐ion cells, thus enabling the complete replacement of LiPF6 and allowing the realization of substantially safer lithium‐ion batteries.
LiTFSI for safety: The utilization of LiTFSI as electrolyte salt in lithium‐ion batteries is enabled by the use of fluorinated carbonates, which form a protective aluminum fluoride film on the current collector surface that avoids anodic dissolution. Electrochemical characterization of state‐of‐the‐art lithium‐ion cells with these new electrolyte solvents reveals that they allow to replace toxic LiPF6 by the chemically and thermally stable and safer LiTFSI as conductive electrolyte salt.
The development of efficient, inexpensive, and safe rechargeable batteries for large-scale environmentally benign cells is one of the key requirements to accommodate and satisfy various technological ...applications. To date, the development of magnesium battery as a promising candidate for next-generation battery systems has been hindered by the lack of high performance and stable electrolyte. In this work, we have developed an original, safe, and high-performance class of electrolytes based on a simple mixture of commercially available compounds, that is, Mg(TFSI)2, anthracene, MgCl2, and diglyme solvent. We have proven that anthracene induces stabilization of the reduced form of magnesium involving reversible magnesium plating/stripping with very high current density. The electrolyte investigated exhibits an unprecedented electrochemical stability window of up to 3.1 V, whereas MgCl2 addition allows the improvement of the Mg/electrolyte interface properties and enables a large cyclability of Mg/Mo6S8 Chevrel phase cell, allowing one to reach high performances.
Due to its high theoretical specific capacity, the lithium/sulfur battery is one of the most promising candidates for replacing current lithium-ion batteries. In this work, we investigate both ...chemical and morphological changes in the electrodes during cycling, by coupling operando spatially resolved X-ray diffraction and absorption tomography to characterize Li/S cells under real working conditions. By combining these tools, the state of the active material in the entire cell was correlated with its electrochemical behavior, leading to a deeper understanding of the performance limiting degradation phenomena in Li/S batteries. Highly heterogeneous behavior of lithium stripping/plating was observed in the anode, while the evolution of sulfur distribution in the cathode depth was followed during cycling.
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•Coordination complexes as an electrochemical sensor for battery electrolyte.•Selective discrimination between the anions present in the electrolyte.•Investigation of electrolyte ...degradation.
Functionalization of a carbon electrode through the electrochemical reduction of ruthenium tris-bipyridine diazonium salts prepared in situ allows determination of the nature of the anions often present in commonly used lithium and sodium battery electrolyte (i.e. PF6− and ClO4−) and also the presence of fluoride anions arising from PF6− degradation. Surprisingly, although these “battery” anions are supposed to exhibit poor coordination ability, their interaction with the electrogenerated RuIII complex is sufficiently strong and reversible to selectively discriminate between the anions ClO4− and PF6− through the observed shift in E°. This study examined the impact of any fluoride present and found a linear relationship between the current response and the F− concentration. This has been applied to ageing LP30 battery electrolyte, confirming the low solubility of LiF in battery electrolyte. This overall behavior could help in the analysis of electrolytes from the recycling sector.
A new class of electrolyte based on TFSI– and triphenolate–borohydride anions was designed and produced which fulfill all requirements of easy synthesis, high ionic conductivity, wide potential ...window, and noncorrosion of Al current collector. The electrolyte composed of magnesium triphenolate borohydride and Mg(TFSI)2 in glyme simultaneously displays a high conductivity of 5.5 mS cm–1 at 25 °C and a reversible Mg plating/stripping with high current density and Coulombic efficiency at room temperature. By addition of a slight amount of MgCl2 to this electrolyte, a Coulombic efficiency of 90% in an SS/Mg cell, stable cycling performance, and a wide anodic potential of 3.4 V vs Mg2+/Mg on Al current collector can be reached. Reversible and efficient Mg insertion/deinsertion with a high capacity of 94 mAh g–1 and 96% Coulombic efficiency was obtained in a Mo6S8 Chevrel cathode phase.
The membrane is a crucial component of Zn slurry–air flow battery since it provides ionic conductivity between the electrodes while avoiding the mixing of the two compartments. Herein, six commercial ...membranes (Cellophane™ 350PØØ, Zirfon®, Fumatech® PBI, Celgard® 3501, 3401 and 5550) were first characterized in terms of electrolyte uptake, ion conductivity and zincate ion crossover, and tested in Zn slurry–air flow battery. The peak power density of the battery employing the membranes was found to depend on the in-situ cell resistance. Among them, the cell using Celgard® 3501 membrane, with in-situ area resistance of 2 Ω cm2 at room temperature displayed the highest peak power density (90 mW cm−2). However, due to the porous nature of most of these membranes, a significant crossover of zincate ions was observed. To address this issue, an ion-selective ionomer containing modified poly(phenylene oxide) (PPO) and N-spirocyclic quaternary ammonium monomer was coated on a Celgard® 3501 membrane and crosslinked via UV irradiation (PPO-3.45 + 3501). Moreover, commercial FAA-3 solutions (FAA, Fumatech) were coated for comparison purpose. The successful impregnation of the membrane with the anion-exchange polymers was confirmed by SEM, FTIR and Hg porosimetry. The PPO-3.45 + 3501 membrane exhibited 18 times lower zincate ions crossover compared to that of the pristine membrane (5.2 × 10−13 vs. 9.2 × 10−12 m2 s−1). With low zincate ions crossover and a peak power density of 66 mW cm−2, the prepared membrane is a suitable candidate for rechargeable Zn slurry–air flow batteries.
The purpose of this study was to investigate a new way of processing cellulose whiskers reinforced polymer. A stable suspension of tunicin whiskers was obtained in an organic solvent ...(N,N-dimethylformamide) without a surfactant addition or a chemical surface modification. Both the high value of the dielectric constant of DMF and the medium wettability of tunicin whiskers were supposed to control the stability of the suspension. The nanocomposite materials were prepared by UV cross-linking using an unsaturated polyether as matrix. The resulting films were characterized by SEM, DSC, and mechanical testing in both the linear and nonlinear domains. The processing technique from a N,N-dimethylformamide suspension was found to be successful and led to materials whose properties are similar to those obtained with aqueous medium. It could be a good alternative to broaden the number of possible polymer matrices and to allow the processing of nanocomposite materials from an organic solvent solution instead of using aqueous suspensions.
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