Synthesis of hexagonal form of tungsten trioxide and electrochemical lithium insertion into the trioxide

The tungsten trioxide hydrate, WO3 . yH(2)O (y = 0.8-1.1) with the hexagonal tungsten bronze (HTB) structure has been prepared by acidification of lithium tungstate solution with strong acid at a concentration of 0.5-1 M and at a temperature of 100 degrees C. On the other hand, hydrothermal synthesis of an acidified lithium tungstate solution at temperatures of 150-200 degrees C leads to the formation of xLi(2)O . WO3 . yH(2)O (x = 0.25-0.30, y = 0.6-0.8) having the HTB structure. The dehydration of WO3 . yH(2)O and xLi(2)O . WO3 . yH(2)O around 350 degrees C leads to the dehydrated trioxides, hexagonal WO3 and xLi(2)O . WO3 with the HTB structure, respectively. The tungsten trioxides prepared have been characterized by X-ray diffractometry, thermogravimetric analysis and electrochemical method. The cyclic voltammetric and galvanostatic measurements revealed that a reversible lithium intercalation into the crystal lattice of hexagonal WO3 takes place with charge-discharge cycling.