Structural characterization and electrochemical reactions with lithium of Cu2CoTixSn3-xS8 solid solutions

The synthesis, structural determination, and electrochemical studies of Cu2 CoTixSn3-xS8 solid solutions are reported. The evolution of the cubic spine l unit cell parameter with x shows two regions which are defined by the inc reasing covalency of the Ti-S bonds and the radii of the metal ions present in the solid. hn increase in the isomer shift of the Sn-119 Mossbauer spec tra of these solids agrees with this interpretation. The solid solutions ar e used as active cathode materials in lithium cells. The discharge shows a complex reduction effect which is associated with the decrease in the oxida tion state of Sn4+ and Ti4+ ions, accompanied by deep structural changes wh ich end in the complete amorphization of the solid and the occurrence of ti n in the metallic state. The extended discharge of the lithium cells leads to a good cycling behavior in galvanostatic experiments carried out in the 0-2.3 V interval, with capacities close to 400 mAh/g after 10 cycles.