Defect Engineering can Enhance the Electrochemical Performance of WS2 for Thermal Batteries

Abstract

As a cathode material for thermal batteries, WS2 has high thermal decomposition temperature and large specific capacity, but it is an intermittent semiconductor, with relatively low conductivity. This low conductivity can prolong the activation time and reduce the discharge specific capacity of thermal batteries. Here, we prepared WS2 with sulfur vacancies through a simple high-temperature annealing method and used electron paramagnetic resonance spectroscopy and X-ray photoelectron spectroscopy to detect the presence of sulfur vacancies. The result shows that sulfur vacancies were successfully introduced in WS2, and the existence of sulfur vacancies can effectively improve the discharge performance of thermal batteries. While maintaining the nanostructure, the thermal decomposition temperature still exceeds 1000 °C, which is far beyond the traditional FeS2 (550 °C) and CoS2 (650 °C) cathodes. The Li-B/LiF-LiBr-LiCl/WS2 with sulfur vacancies (treated at 500 °C) couple has higher discharge specific capacity (when the cut-off voltage is 0.5 V, it is 380.58 mAh g−1, which is 14.85% higher than the original WS2) and lower total polarization (about 21% lower than original WS2). This work provides a beginning for further study of sulfur vacancies defect materials as the cathode of thermal batteries.