Thermal batteries are a type of thermally activated reserve batteries, where the cathode material significantly influences the operating voltage and specific capacity of the battery. In this work, VS4-VO2 has been synthesized through the hydrothermal method and used as the cathode material for thermal batteries. Firstly, the material with the VS4 crystallinity is obtained at 170 °C and the mass percentages of VS4/VO2 are 63.1 % and 36.9 %, respectively. The formation mechanism of VS4-VO2 has been proposed based on in-situ ultraviolet (UV) spectrum, which shows that the hydrolysis product S2- under alkaline conditions promotes the formation of VS4. To further improve the conductivity of the material, the reduced graphene oxide (rGO) has been introduced into VS4-VO2 nanomaterials. When applied in thermal batteries, the rGO-VS4-VO2 composite exhibits a voltage plateau of approximately 2.4 V and a discharging specific capacity of 327 mAh/g with the cut-off voltage of 1.5 V at 50 mA and 350°C, which are higher than those of VS4-VO2. Furthermore, the discharge mechanisms of rGO-VS4-VO2 in thermal batteries have been analyzed, which indicates that VS4-VO2 involves two processes of phase transformation, including the intercalation process and conversion process. The results confirm rGO-VS4-VO2 as a promising cathode material for thermal batteries.
Keywords: Cathode; High-voltage; Thermal battery; Vanadium sulfide.
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