Functionalized imidazolium ionic liquids as electrolyte components of lithium batteries

Some basic properties and compatibility toward lithium electrode for electrolytes based on substituted imidazolium ionic liquid have been investigated. The ionic liquids having imidazolium cation substituted by methylcarboxyl or cyano group suffers from low conductivity. However, reversible lithium deposition–dissolution process was observed in electrolytes based on these electrolytes. In particular, lithium salt solution in cyanomethyl-substituted imidazolium ionic liquid provided similar cycle efficiency to conventional organic solvent electrolyte at constant-current condition. The mixed ionic liquid electrolyte containing the cyanomethyl-substituted ionic liquid also provided good cycle performance despite of containing large amount of 1-ethyl-3-methyl imidazolium (EMI)-based ionic liquid. Such mixed electrolyte system serves both the stability of lithium electrode process and valid conductivity for practical use.     

Formation of a nanogroove-striped NiO surface using atomic steps

A nanogroove-striped pattern was formed on a NiO film surface. The periodic nanopattern was successfully obtained over the entire surface via high-temperature annealing of the epitaxial NiO thin film, which was grown on an atomically stepped sapphire substrate at low temperature. The depth, width and interval of straight nanogrooves were about 3?nm, 35?nm and about 100?nm, respectively. The periodicity of the stripe agrees well with that of the atomic steps of the substrate.     

Influence of particle size on the self-discharge behavior of graphite electrodes in lithium-ion batteries

Self-discharge characteristics of synthetic graphite electrodes with different particle sizes have been investigated by electrochemical and analytical methods. Variations of open-circuit potential (OCP), residual capacity and electrochemical impedance responses were monitored during or after the storage at different temperatures. The rate of self-discharge depended on the particle size, or the specific surface area, of the graphite sample. The temperature dependence of the self-discharge rate revealed that the activation energy for the process does not depend on the particle size of the graphite electrode. The ac impedance responses suggest that the self-discharge processes consist of the loss of the Li species in the graphite and SEI (Solid-Electrolyte-Interphase) formation at the graphite surface. The latter SEI formation process was found to be dependent on the surface site, edge or basal planes, from the results of surface observation and elemental analyses.