Single-phase Fe0.5Co0.5S2 cathode material for long working time thermal batteries.

Multi-metal disulfides are widely employed as cathode materials for thermal batteries owing to their high electronic conductivity, high specific capacity, and exceptional stability of the cathode-separator interface. However, conventional synthesis methods for multi-metal disulfides suffer from low production efficiency. Herein, we report a scalable route to synthesize Fe-Co binary disulfide (Fe0.5Co0.5S2) via high-temperature solid-state sintering of a mixture of Fe-Co alloy and sublimed sulfur. The resulting Fe0.5Co0.5S2 possesses single-phase, high thermal stability, and low resistance, which effectively enhance its discharge capacity in thermal batteries. At a current density of 100 mA cm-2 and a discharge temperature of 460 °C, Fe0.5Co0.5S2 delivers a high specific capacity of 595.4 mAh g-1 with a cutoff voltage of 1.5 V. Notably, the specific capacity decreases by only 10.7% at a discharge temperature of 540 °C, indicating an extended working temperature range. As a result, the voltage upon constant and pulse current loading of Fe0.5Co0.5S2 in a 102 V thermal battery is obviously higher than that of the mechanically mixed FeS2/CoS2. This work provides a simple and efficient strategy for the preparation of binary disulfides for thermal batteries.