Coatings based on the alternate adsorption of oppositely charged species constitute a promising way to confer new functionalities on the surfaces of materials in an easy manner. Up to now, the deposition of polyelectrolyte multilayer films has been limited to substrates of small surface areas mainly for biomedical applications and high added value microelectronics. The interest of such coatings will increase and their application field will broaden if new methods allowing to speed up their deposition and allowing for upscalling to macroscopic substrates will be available.The main objective of the ”EnergyCell” project is to propose a method to deposit films of similar properties as polyelectrolyte multilayer films on macroscopic substrates for fuel cell applications : the design of fast prepared and long lasting electrodes for fuel cells. The films will be constituted from polyelectrolyte-polyelectrolyte and polyelectrolytes-nanoparticles complexes instead individual polyelectrolytes and they will be deposited by means of spray deposition methods. This project will be performed in order to use the equivalent of polyelectrolyte multilayer films, prepared by horizontal spray of complexes, in fuel cell applications. For such applications, membranes of controlled proton permeability and electrical conductivity are required.Before the development of up-scalling methods, a large part of the project will be devoted to an investigation aimed at a better understanding of the coalescence of polyelectrolyte complexes, which is mandatory to form homogeneous films from those complexes during the spraying process.