N. Kumagai et al., THERMODYNAMICS AND KINETICS OF ELECTROCHEMICAL INTERCALATION OF LITHIUM INTO LI0.50WO3.25 WITH A HEXAGONAL TUNGSTEN BRONZE STRUCTURE, Solid state ionics, 98(3-4), 1997, pp. 159-166
The kinetics and thermodynamics of electrochemical intercalation of li
thium into Li0.50WO3.25 with a hexagonal tungsten bronze structure pre
pared by a solution technique were studied with an ac impedance method
, open-circuit potential and X-ray diffraction measurements. The open-
circuit-potential versus x-in-Li-x[Li0.50WO3.50]-curve consists of two
straight lines with different slopes, which were related to the struc
tural variation in the oxide with lithium intercalation. The standard
Gibbs energy for lithium intercalation, Delta G(1)(0), was -252.6 W/mo
l in the range from x to 1 in Li-x[Li0.50WO3.25] at 25 degrees C. The
chemical diffusion coefficients, (D) over tilde, of lithium intercalat
ion into oxide, were measured by ac impedance method as functions of d
epth of lithium intercalation and temperature in 1 M LiClO4/propylene
carbonate solution. The calculated (D) over tilde values were of the o
rder of 10(-9) cm(2)/s and the activation energy for lithium diffusion
was 35-44 kJ/mol, being typical of diffusion in layered intercalation
materials. Furthermore, the lithium diffusion coefficient and the act
ivation energy for lithium diffusion in Li0.50WO3.25 were compared wit
h hexagonal WO3 and hexagonal-type A(n)WO(3+n/2) (n = 0.14-0.28, A = N
a+, K+, NH4+).