Preparation of Li_(4.4)Si Alloy by Use of Mechanical Milling Methods and Its Properties as Negative Electrodes in Lithium Cells

摘要

Meta-stable phase Li_(4.4)Si was prepared by mechanical milling process. In order to investigate the electrochemical properties of the meta-stable Li_(4.4), two types of electrochemical cells were used; one of them was three-electrolyte a-60Li_2Scentre dot 40SiS_2, which was also prepared by mechanical milling process and showed high Li ion conductivity of 1.8X10~4 Scm~(-1) at room temperature. Electrochemical capacity of the meta-stable Li_(4.4)Si was about 400mAhg~(-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 Li_(4.4)Si brought about the reaction between the Li_(4.4)Si 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 TiS_2 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.