Structural and electrochemical study of Li+ insertion in the infrared reflectance modulating compound LixWO3·H2O

The structural and electrochemical behavior of o-LixWO3·H2O has been studied for several electrochemical Li intercalation/deintercalation processes. Four intercalated phases called α, β, γ and δ, were distinguished by means of in situ X-ray diffraction (XRD) experiments. The modification in the distance between the tungsten layers represented by the cell lattice parameter b was found to reflect the structural changes induced by Li intercalation. Thus, we found that potential cycling over the α phase (till x=0.35) does not lead to any major degradation of the structure whereas reducing further WO3·H2O and reaching the β, γ or δ phase introduces irreversible damages. Furthermore, the α intercalation domain divides into three subphases called α0, α1 and α2. From the less intercalated phase to the most intercalated one, the structure exhibits increasing higher symmetry. The unintercalated orthorhombic cell (α0 phase) first changes into a quasi-quadratic one where a≈c≠b/2 (α1 phase) and finally to a quasi-quadratic one where a≈c≈b/2 (α2 phase). The knowledge of this intercalation behavior is essential to improve the performance of a recently built WO3·H2O-based variable infrared reflectance plastic device.