The preparation and characterisation of WO3.1/3H(2)O phase, which is an intermediate to hexagonal tungsten oxide was performed. Tungsten oxide dihydrate was precipitated from acidified sodium tungstate solution. Two and three washing steps have been applied to the as-obtained amorphous gel. WO3.1/3H(2)O nanograins have been obtained after the hydrothermal process performed at 140 degrees C, for 24 hours in an acid digestion bomb. A spin coater was used for thin film preparation. Structural, morphological and optical characterisation as well as electrochemical performance of thin films were determined by scanning electron microscopy, atomic force microscopy, Raman spectroscopy and cyclic voltammetry. The ion insertion properties of WO3.1/3H(2)O films show strong correlation to the close packed structure and to the presence of structural water.