Scalable Preparation and Improved Discharge Properties of FeS2@CoS2 Cathode Materials for High-Temperature Thermal Battery.

Long-time thermal batteries with high specific energy are crucial for improving the fast response ability of long-range weapons. Due to its high capacity, safety, and stability, the new sulfide cathode has attracted extensive attention. In this study, an FeS2@CoS2 composite cathode with a core-shell structure was prepared via a combination of hydrothermal and high-temperature vulcanization processes. The novel FeS2@CoS2 cathode not only delivers a high discharge voltage and output capacity, but also has high thermal stability and excellent conductivity. Benefiting from the synergistic effect of FeS2 and CoS2, the as-synthesized cathode yields a high specific capacity. At a large current density of 1 A/cm2, the utilization rate of FeS2@CoS2 cathode material can reach 72.33%, which is 8.23% higher than that of FeS2. Moreover, the maximum output capacity is up to 902 As/g, with a utilization rate of 79.02% at 500 mA/cm2. This novel design strategy holds great promise for the development and application of high-performance thermal batteries in the future.

Recent Developments of Cathode Materials for Thermal Batteries.

Big progress has been made in batteries based on an intercalation mechanism in the last 20 years, but limited capacity in batteries hinders their further increase in energy density. The demand for more energy intensity makes research communities turn to conversion-type batteries. Thermal batteries are a special kind of conversion-type battery, which are thermally activated primary batteries composed mainly of cathode, anode, separator (electrolyte), and heating mass. Such kinds of battery employ an internal pyrotechnic source to make the battery stack reach its operating temperature. Thermal batteries have a long history of research and usage in military fields because of their high specific capacity, high specific energy, high thermal stability, long shelf life, and fast activation. These experiences and knowledge are of vital importance for the development of conversion-type batteries. This review provides a comprehensive account of recent studies on cathode materials. The paper covers the preparation, characterization of various cathode materials, and the performance test of thermal batteries. These advances have significant implications for the development of high-performance, low-cost, and mass production conversion-type batteries in the near future.

Cobalt-Doped NiS2 Micro/Nanostructures with Complete Solid Solubility as High-Performance Cathode Materials for Actual High-Specific-Energy Thermal Batteries.

Transition-metal sulfides are key cathode materials for thermal batteries used in military applications. However, it is still a big challenge to prepare sulfides with good electronic conductivity and thermal stability. Herein, we rapidly synthesized a Co-doped NiS2 micro/nanostructure using a hydrothermal method. We found that the specific capacity of the Ni1-xCoxS2 micro/nanostructure increases with the amount of Co doping. Under a current density of 100 mA cm-2, the specific capacity of Ni0.5Co0.5S2 was about 1565.2 As g-1 (434.8 mAh g-1) with a cutoff voltage of 1.5 V. Owing to the small polarization impedance (5 mΩ), the pulse voltage reaches about 1.74 V under a pulse current of 2.5 A cm-2, 30 ms. Additionally, the discharge mechanism was proposed by analyzing the discharge product according to the anionic redox chemistry. Furthermore, a 3.9 kg full thermal battery is assembled based on the synthesized Ni0.5Co0.5S2 cathode materials. Notably, the full thermal battery discharges at a current density of 100 mA cm-2, with an operating time of about 4000 s, enabling a high specific energy density of around 142.5 Wh kg-1. In summary, this work presents an effective cathode material for thermal battery with high specific energy and long operating life.