In all-solid-state Li ion batteries, solid electrolyte layers must be fabricated without an annealing process because of the reaction between electrolytes and active materials. Hence, a lot of researchers have an interest in the aerosol deposition (AD) films which can be formed at room temperature and show dense microstructures without an annealing process. In this study, the microstructure and ionic conductivity of an Al2O3-added Li7La3Zr2O12 (LLZ) AD film were investigated. The LLZ AD film showed the dense microstructure which had nano-size grains. Because of the small grain size, low electric conduction was observed at a LLZ AD film. In addition, the moisture in air might be also responsible for the low electric conduction. In order to demonstrate the Li ion conduction in a LLZ AD film, a solid state cell was fabricated using a C-coated LiFePO4 (LFP) AD film as a working electrode [structure: LFP AD film/LLZ AD film (solid electrolyte)/Li foil]. The electrochemical properties of the solid state cell were compared with them of a liquid electrolyte cell [structure: LFP AD film/Liquid electrolyte/Li foil]. (C) 2014 The Electrochemical Society. All rights reserved.