Suppressing self-discharge of Li-B/CoS₂ thermal batteries by using a carbon-coated CoS₂ cathode

Thermal batteries with molten salt electrolytes are used for many military applications, primarily as power sources for guided missiles. The Li-B/CoS₂ couple is designed for high-power, high-voltage thermal batteries. However, their capacity and safe properties are influenced by acute self-discharge that results from the dissolved lithium anode in molten salt electrolytes. To solve those problems, in this paper, carbon coated CoS₂ was prepared by pyrolysis reaction of sucrose at 400 °C. The carbon coating as a physical barrier can protect CoS₂ particles from damage by dissolved lithium and reduce the self-discharge reaction. Therefore, both the discharge efficiency and safety of Li-B/CoS₂ thermal batteries are increased remarkably. Discharge results show that the specific capacity of the first discharge plateau of carbon-coated CoS₂ is 243 mA h g^-1 which is 50 mA h g^-1 higher than that of pristine CoS₂ at a current density of 100 mA cm^-2. The specific capacity of the first discharge plateau at 500 mA cm^-2 for carbon-coated CoS₂ and pristine CoS₂ are 283 mA h g^-1 and 258 mA h g^-1 respectively. The characterizations by XRD and DSC indicate that the carbonization process has no noticeable influence on the intrinsic crystal structure and thermal stability of pristine CoS₂.