Structure and electrochemistry of LixWO2

Using in situ X-ray diffraction and electrochemical techniques the structure and phase diagram of LixWO2 for 0<x<1 has been determined. As x increases, the compound has three monoclinic phases separated by first-order phase transitions. As x decreases, some parts of the material return to x=0 by these same phase transitions, but in other parts the second phase is orthorhombic, not monoclinic. The orthorhombic phase has x∼0.5, and is only formed as x is decreasing from larger values. Electrochemical cells lose capacity when discharged past x∼0.5, and this loss may be associated with the orthorhombic phase. If the cells is discharged past x=1, LixWO2 undergoes an irreversible decomposition. (author). 11 refs.; 9 figs.; 2 tabs