Iron trifluoride (FeF 3 ) 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 FeF 3 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 FeF 3 had a hierarchical structure and a decomposition threshold temperature of 800°C. At a current density of 100 mA cm −2 , the Li-B/FeF 3 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 to 10 m . In specific, the Li-B/ FeF 3 -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 FeF 3 as a high-voltage cathode material for high-power thermal batteries.