Mono- and bi-layers of polyethylene oxide (PEO) have been incorporated into the interlayer gap of A_xMoO₃, to give ordered (PEO)_x[Na(H₂O)_n]_0.25MoO₃ nanocomposites (x= 0.40, mono-; or 0.90, bi-) with interlayer distances of 12.9 and 15 Å, respectively. The driving force for the insertion reaction arises from the solvation of the cations by the PEO, together with the increase in entropy resulting from displacement of water molecules from the interlamellar region. We propose a model for the structure of the monolayer and bilayer composites based on X-ray diffraction, ¹³C/²³Na solid-state NMR and IR data. We have carried out a preliminary comparative study of the electrochemical insertion of lithium into the two polymer nanocomposites by using the materials as cathodes in rechargeable lithium batteries. Li can be reversibly inserted into both materials. Lithium ion transport is substantially enhanced in the bilayer nanocomposite as a result of PEO incorporation, compared with the monolayer nanocomposite. The monolayer composite also shows a pronounced decrease in cell capacity on cycling by comparison to the bilayer.