Structure and dynamics of highly concentrated LiTFSI/acetonitrile electrolytes.

High salt concentration has been shown to induce increased electrochemical stability in organic solvent-based electrolytes. Accompanying the change in bulk properties is a structural ordering on mesoscopic length scales and changes in the ion transport mechanism have also been suggested. Here we investigate the local structure and dynamics in highly concentrated acetonitrile electrolytes as a function of salt concentration.

Pressure and Temperature Dependence of Local Structure and Dynamics in an Ionic Liquid.

A detailed understanding of the local dynamics in ionic liquids remains an important aspect in the design of new ionic liquids as advanced functional fluids. Here, we use small-angle X-ray scattering and quasi-elastic neutron spectroscopy to investigate the local structure and dynamics in a model ionic liquid as a function of temperature and pressure, with a particular focus on state points (,) where the macroscopic dynamics, i.e.

Density scaling of structure and dynamics of an ionic liquid.

Room temperature ionic liquids are salts with low melting points achieved by employing bulky and asymmetrical ions. The molecular design leads to apolar and polar parts as well as the presence of competing Coulomb and van der Waals interactions giving rise to nano-scale structure, e.g.

Experimental Evidence for a State-Point-Dependent Density-Scaling Exponent of Liquid Dynamics.

A large class of liquids obey density scaling characterized by an exponent, which quantifies the relative roles of temperature and density for the dynamics. We present experimental evidence that the density-scaling exponent γ is state-point dependent for the glass formers tetramethyl-tetraphenyl-trisiloxane (DC704) and 5-polyphenyl ether (5PPE). A method is proposed that from dynamic and thermodynamic properties at equilibrium estimates the value of γ.

Isochronal superposition and density scaling of the -relaxation from pico- to millisecond.

The relaxation dynamics in two van der Waals bonded liquids and one hydrogen-bonding molecular liquid are studied as a function of pressure and temperature by incoherent neutron scattering using simultaneous dielectric spectroscopy. The dynamics are studied in a range of alpha relaxation times from pico- to milliseconds, primarily in the equilibrium liquid state. In this range, we find that isochronal superposition and density scaling work not only for the two van der Waals liquids but also for the hydrogen-bonding liquid, though the density scaling exponent is much smaller for the latter.

High-pressure cell for simultaneous dielectric and neutron spectroscopy.

In this article, we report on the design, manufacture, and testing of a high-pressure cell for simultaneous dielectric and neutron spectroscopy. This cell is a unique tool for studying dynamics on different time scales, from kilo- to picoseconds, covering universal features such as the α relaxation and fast vibrations at the same time. The cell, constructed in cylindrical geometry, is made of a high-strength aluminum alloy and operates up to 500 MPa in a temperature range between roughly 2 and 320 K.