2001 年 48 巻 3 号 p. 267-273
Meta-stable phase Li4.4Si was prepared by mechanical milling process. In order to investigate the electrochemical properties of the meta-stable Li4.4si, two types of electrochemical cells were used; one of them was three-electrode cell with usual liquid electrolyte LiPF6-EC/DMC, and the other was all solid state cell with solid electrolyte a-60Li2S⋅40SiS2, which was also prepared by mechanical milling process and showed high Li+ ion conductivity of 1.8×10-4 Scm-1 at room temperature. Electrochemical capacity of the meta-stable Li4.4Si was about 400 mAhg-1 for Li+ ion extraction in the liquid electrolyte. The capacity was decreased with an increase in the number of Li+ extraction-insertion cycles. The Li+ extraction and insertion from the meta-stable Li4.4Si brought about the reaction between the Li4.4Si sample and metallic Cu, which was used as a collector of electronic current. Electrochemical extraction of Li+ ions from the meta-stable phase showed the capacity exceeding 250mAhg-1 for the all-solid state cell using the solid electrolyte and TiS2 as counter electrode. In this solid state cell, the meta-stable phase showed almost no structural change during the extraction and insertion of Li+ ions.