The conducting salt in lithium-ion batteries, LiPF6, can react with water contaminations in the battery electrolyte, releasing HF and further potentially harmful species, which decrease the battery performance and can become a health hazard in the case of a leakage. In order to quantify the hydrolysis products of LiPF6 in a water-contaminated battery electrolyte (1 mol L–1 LiPF6 in EC/DEC) and in aqueous solution, ion chromatography (IC), coulometric Karl Fischer titration (cKFT), and acid–base titration were used on a time scale of several weeks. The results show that the nature of the hydrolysis products and the kinetics of the LiPF6 hydrolysis strongly depend on the solvent, with the main reaction products in the battery electrolyte being HF and HPO2F2. From the concentration development of reactants and products, we could gain valuable insight into the mechanism of hydrolysis and its kinetics. Since the observed kinetics do not follow simple rate laws, we develop a kinetic model based on a simplified hydrolysis process, which is able to explain the experimentally observed kinetics.

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The solid electrolyte interphase (SEI) is a complex and fragile passivation layer with crucial importance for the functionality of lithium-ion batteries. Due to its fragility and reactivity, the use of in situ techniques is preferable for the determination of the SEI's true structure and morphology during its formation. In this study, we use in situ neutron reflectometry (NR) and in situ atomic force microscopy (AFM) to investigate the SEI formation on a carbon surface. It was found that a lithium-rich adsorption layer is already present at the open circuit voltage on the carbon sample surface and that the first decomposition products start to deposit close to this potential. During the negative potential sweep, the growth of the SEI can be observed in detail by AFM and NR. This allows precise monitoring of the morphology evolution and the resulting heterogeneities of individual SEI features. NR measurements show a maximum SEI thickness of 192 Å at the lower cutoff potential (0.02 V vs Li/Li), which slightly decreases during the positive potential scan. The scattering length density (SLD) obtained by NR provides additional information on the SEI's chemical nature and structural evolution.

Efficient and green exfoliation of bulk MoS2 into few-layered nanosheets in the semiconducting hexagonal phase (2H-phase) remains a great challenge. Here, we developed a new method, water-assisted exfoliation (WAE), for...

Morphological changes of a conductive polymer in an ionic liquid during charging and discharging.