The kinetic and thermodynamic studies of the insertion of lithium into hexagonal-type x(A20). WO3 (A = Na § K*, or NHI, x = 0.05 ~ 0.14), obtained by heat-treating the corresponding tungstic acid C phases, x(A20) . WO3 -y(H20) (x = 0.069 ~ 0.14, y = 0.38 ~ 0.74), at 350~ in air, were made. The variations of quasi-open-circuit potentials and x-ray diffraction patterns of the tungsten oxides with lithium insertion revealed that a ternary phase, such as Li, {x (A20) 9 WO3}, is formed, while maintaining the original hexagonal-type structure. The standard free energies for lithium insertion, AG~ ~ er -1 + + + .... w e -375, -389 and -400 kJ(mo~ at 298 K for A = Na, K, and NH~ m L12{x(A20) 9 WO3}, respectively. The chemmal diffusion coefficients of lithium, D, in the oxides were measured as functions of the lithium composition and temperature by an ac impedance method using 1M LiC1Q-propylene carbonate as an electrolyte. The obtained values of D, based on a geometrical surface area, were dependent on the lithium composition and temperature. The values of D for Li~ {x (A20) 9 WO3} (A = Na § K § NH~) were approximately 10 -8 cm 2 s -~ at n = 0.5 and room temperature, decreasing to 10 -l~ cm 2 s -~ with increasing n-value. The self-diffusion coefficient of lithium, DL~, derived from the D values, was of the order of 10 -1~ cm 2 s < at n = 0.5 and room temperature, decreasing with increasing n-values. Both the values of D and DL~ for the hexagonaltype oxides were by several orders of magnitude higher than those for the monoclinic WQ. The activation energies for lithium diffusion in Li~ {x (A20) 9 WO3} (A = Na +, NH~, n = 0.5 ~ 2) were 20 ~ 30 kJ(mo]) -~, being typical of diffusion in layered insertion materials 9 oxides were obtained mainly according to an ac impedance method} 2 In this method the following equation was usedAw is a Warburg prefactor in the Warburg impedance Zw = (1 -J)Aw ~/"~ for semi-infinite diffusion (o radical frequency). Molar volumes Vm for x(A20) -WO~ (A ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 132.174.255.116 Downloaded on 2015-03-10 to IP