Novel multi-component molten salt systems containing iodides, LiF-LiBr-Lil, LiF-NaBr-Lil, and LiF-LiCl-LiBr-Lil, were investigated for use as electrolytes in high temperature molten salt batteries to improve the discharge rate-capability. The iodide-based molten salts showed higher ionic conductivity (similar to 3 S cm(-1) at 500 degrees C) than conventional LiCl-KCl, and had low enough melting points (below 400 degrees C that can be used in practical high temperature molten salt batteries. The iodide-based salts showed instability at temperatures higher than 280 degrees C in dried air. The decomposition mechanism of iodide-based molten salts was discussed, and it was found that elimination of oxygen from the environment is effective to stabilize the iodide-based molten salts at high temperatures. (C) 2009 Elsevier B.V. All rights reserved.