Hikaru Sano

Effect of Organic Additives on Electrochemical Properties of Li Anode in Room Temperature Ionic Liquid

Li metal rechargeable batteries have attracted much attention as a candidate for post-Li-ion batteries with higher power voltage and higher energy density. The application of room temperature ionic liquids (RTILs) to the electrolyte instead of nonaqueous electrolytes has been studied with the aim of improvement of the film property on the Li metal/electrolyte interface in order to put the Li metal rechargeable batteries into practice. In this study, the behaviors of Li plating and plating―stripping cycle property were investigated with organic additives [vinylene carbonate (VC) or ethylene sulfite (ES)] added to an RTIL (PP13[TFSA]). A more circular shape of deposit is obtained just after first plating when the organic additives are used, indicating that the organic additives suppress the local growth of Li deposition. Better cycling property and reproducibility are obtained when the organic additives are used, which is consistent with the result after first plating. Therefore, using additives in combination with RTIL-based electrolytes is advantageous.

Molecular ion battery: a rechargeable system without using any elemental ions as a charge carrier

Is it possible to exceed the lithium redox potential in electrochemical systems? It seems impossible to exceed the lithium potential because the redox potential of the elemental lithium is the lowest among all the elements, which contributes to the high voltage characteristics of the widely used lithium ion battery. However, it should be possible when we use a molecule-based ion which is not reduced even at the lithium potential in principle. Here we propose a new model system using a molecular electrolyte salt with polymer-based active materials in order to verify whether a molecular ion species serves as a charge carrier. Although the potential of the negative-electrode is not yet lower than that of lithium at present, this study reveals that a molecular ion can work as a charge carrier in a battery and the system is certainly a molecular ion-based “rocking chair” type battery.