Li2Se-Cu3Se2 nanocomposites with a highly heterogeneous mixture have been fabricated by pulsed laser deposition method. The Li releasing process from the as-deposited Li2Se-Cu3Se2 nanocomposites thin film during the first charging was confirmed by the glvanostatic cycling and cyclic voltammetry measurements. By using ex situ X-ray diffraction, X-ray photoelectron spectra, transmission electron microscopy, and selected-area electron diffraction measurements, the decomposition of Li2Se driven by Cu3Se2 under the electrochemical potential was revealed. In the first cycle, the oxidation peak at 3.8 V and the reduction peaks at 2.1 V could be attributed to the decomposition and formation of Li2Se with the conversion reaction of Cu3Se2 into CuSe2. Our findings demonstrated that amorphous or nanocomposite Li2Se-Cu3Se2 can possess very high electrochemical activity. These results presented a special case of solid-state heterogeneous electrochemistry with both nanostructured binary materials. (c) 2007 The Electrochemical Society.