Yasuharu Yamamura

New lithium ion conductors based on Li2S-SiS2 system

Abstract There is great interest in sulfide glasses because of their high lithium ion conductivity. We have synthesized a new lithium ion conductive solid electrolyte based on Li 2 S-SiS 2 glass with the composition: 0.03Li 3 PO 4 -0.59Li 2 S-0.38SiS 2 at ambient pressure by quenching in liquid nitrogen. Its conductivity at room temperature was 6.9×10 −4 S cm −1 . The stability of the glass towards electrochemical reduction was dramatically improved compared with SiS 2 -Li 2 S-LiI glass. The glass synthesized with Li 2 SO 4 instead of Li 3 PO 4 also indicated good conductivity and stability against electrochemical reduction.

Photo-rechargeable solid state battery

Photoelectrochemical reactions on a semiconductor electrode (P-I aSi/SiO x ) with a silver ion conductive solid electrolyte (Ag 6 I 4 WO 4 ) have been investigated and photo-sensitizing effect was observed. On the basis of this reaction, photo-battery was examined which had a capability of self-charging under the sun or fluorescence illuminations. The battery consist of two parts. One is a MIS-type photovoltaic part (ITO/P-I as aSi/SiO x /Ag), and another is its energy storage part (Ag x V 2 O 5 /Ag 6 WO 4 /Ag x− V 2 O 5 ). Behaviors of photo reactions and the electrochemical characteristics in this system are discussed

A new synthetic method for Chevrel-phase compounds

Abstract Ternary molybdenum chalcogenides called Chevrel-phase compounds are useful materials as superconductors or electrode materials in secondary batteries. But the ordinary synthetic method of Chevrel phase compound has not been convenient for a large scale preparation because of possibility of a burst caused by high vapor pressure of sulfur, which is one of the starting materials inside the sealed tube during the procedure. We developed a new synthesizing method which fits to a large scale preparation by using MoS2 as a starting material and non-sealed tube as a reaction tube to avoid the danger. We also investigated the electrochemical and superconducting properties of the obtained compounds and found out that the obtained compounds are almost the same as the ones obtained by an ordinary method.

Rechargeable solid-state batteries with silver ion conductors

Abstract Electrochemical behaviors of silver vanadium bronzes (Ag x V 2 O 5 ) with silver ion conductor (Ag 6 I 4 WO 4 ) were investigated in 0.3≦ x ≦1.0. Coulometric titration curves of these bronzes indicated that δ-phase bronze was available as electrode materials in solid-state cells using silver ion conductors. Properties of the rechargeable solid-state battery system (Ag 0.7 V 2 O 5 /Ag 6 I 4 WO 4 / Ag 0.7 V 2 O 5 ) were examined, and this battery showed excellent reversibility, stability, and shelf life in open-air and at high temperature.