Junko Ide

Application of Lithium Metal Electrodes to All-Solid-State Lithium Secondary Batteries Using Li3 PO 4 ­ Li2 S ­ SiS2 Glass

The Li 3 PO 4 -Li 2 S-SiS 2 glass electrolyte exhibited instability against a Li metal electrode in the charge-discharge cycle using a LiCoO 2 positive electrode. The interface products between the Li electrode and the glass electrolyte were investigated by Si and S-K edge near-edge X-ray absorption fine structure analyses. It was suggested that Li 2 S and Si coordinated to three sulfur atoms formed after charge-discharge cycles. This side reaction could be suppressed by modifying the surface of Li metal by N 2 gas, leading to improvement of the charge-discharge property compared to unmodified Li electrode. The operating voltage attained to about 4 V in the modified Li/Li 3 PO 4 -Li 2 S-SiS 2 glass electrolyte/LiCoO 2 cell, which was comparable to Li-ion battery using a liquid electrolyte.

Glass Formation in the MoO3-La2O3-Nd2O3 System

Novel low melting glasses in the MoO3-La2O3-Nd2O3 system were obtained at different cooling rates (102 K/s and 104-105 K/s). Characterization of the amorphous samples was made by differential thermal analysis (DTA) and X-ray absorption fine structure (XAFS) method. According to DTA data of the glass samples, the glass transition temperatures are at 325-330 0C, the crystallization started above 410 0C and the melting temperatures are at 660-720 0C. A structural model of glasses was suggested on the basis of XAFS and IR investigations. It was shown that the predominant structural units in the amorphous network of glasses containing 90 -80 mol% MoO3 are MoO6 groups. The appearance of MoO4 groups deteriorates the glass formation ability.