The kinetics and thermodynamics of electrochemical intercalation of li
thium into hexagonal WO3 prepared by a solution technique were studied
with an a.c. impedance method, open-circuit potential and X-ray diffr
action measurements. The open-circuit potential-x in LixWO3 curve cons
ists of two straight lines with different slopes, which was related to
the structural variation in the oxide with lithium intercalation. The
standard Gibbs energy of lithium intercalation, Delta G(l)(0), was -2
39.4 kJ/mol in the range of x from 0 to 1 in LixWO3 at 25 degrees C. T
he chemical diffusion coefficient of lithium, (D) over tilde, for the
intercalation into the oxide, was measured by a.c. impedance method as
functions of depth of lithium intercalation and temperature in 1 M Li
ClO4/propylene carbonate solution. The results showed that the Warburg
impedance was linearly related to omega(-1/2) (omega: angular frequen
cy) and the ((D) over tilde) values obtained decreased with an increas
e in lithium concentration in the oxide, being one-two orders of magni
tude higher than that in monoclinic WO3. Furthermore, the lithium diff
usion coefficient of lithium and the activation energy for the diffusi
on were also obtained as a function of x-value in LixWO3.