Iron trifluoride (FeF3) might be a suitable high-voltage cathode material for high-power thermal batteries due to its high voltage plateau, low cost and low toxicity. In this study, anhydrous FeF3 was synthesized and its applicability as a cathode material for thermal batteries was investigated. Its structure, thermal stability and electrochemical properties were also studied. The synthesized anhydrous FeF3 had a hierarchical structure and a decomposition threshold temperature of 800 degrees C. At a current density of 100 mA cm(-2), the Li-B/FeF3 single cell exhibited an initial discharge voltage of 3.20 V and a specific capacity of 81.9 mA h g(-1) with a cutoff voltage of 2.0 V. Moreover, multi-walled carbon nanotubes (MWCNTs) were used as the conductive agents, leading to an decreasing of the total polarization from 45 m Omega to 10 m Omega. In specific, the Li-B/FeF3-MWCNTs single cell exhibited an initial discharge voltage of 3.27 V and a specific capacity of 160.7 mAh.g(-1). This work provides a beginning for further applying FeF3 as a high-voltage cathode material for high-power thermal batteries. (C) 2019 The Electrochemical Society.