Well-crystallized and homogeneous LiFePO4 films, of the order of 300 nm thick, have been grown by pulsed laser deposition on Pt-capped Si substrates in a one-step process. Their intrinsic lithium insertion properties have been evaluated both in aqueous and nonaqueous electrolytes. The films show the electrochemical fingerprint characteristic of pure triphylite LiFePO4, with, namely, equilibrium voltage at 3.42 V vs. Li+/Li. While carbon-free, the kinetic of the insertion/deinsertion process in such films compared favorably with those of optimized carbon-coated LiFePO4 powders. Furthermore, we demonstrate sensor responses of these thin-film LiFePO4 electrodes toward the quantitative detection of Li+ ions in aqueous solutions as long as their concentration ranges from 10(-4) to 1 M. (C) 2003 The Electrochemical Society.