Exploring High-Voltage Sulfate Cathodes for Low-Temperature Thermal Batteries

Thermal batteries have high specific energy and can operate in harsh environments, making them suitable for military and aerospace applications. However, existing cathode materials do not meet the high power and energy density requirements of advanced military systems. This urgent need motivates the development of new high-performance cathodes. Sulfates, as polyanionic compounds with highly electronegative anions, often exhibit higher voltages than phosphates. This high voltage should match the high power output needs of thermal battery cathode, though few studies explore sulfate. In this of case, NiSO₄, CoSO₄, and CuSO₄ were investigated as cathode materials for thermal battery. They all have higher voltage and greater specific capacity at 450 °C (cut-off voltage is 75% of peak voltage) than at 500 °C or higher. Compared with other temperatures, the peak voltage of CoSO₄ cathode at 450 °C is 2.23 V and the specific capacity is 296 mAh g⁻¹. While CuSO₄ showed modest capacity at 450 °C, its high voltage of 2.5 V makes it a promising high energy density cathode. This work provides new insights into cathode materials for high power and energy density thermal batteries.