Structured confinement effects of hierarchical V2O5 cathodes to suppress flow of molten salt in high specific energy thermal batteries with binder-free MgO

Abstract Despite the excellent thermal/air stability and high discharge voltage of V2O5 cathodes in thermal batteries, their poor conductivity must be overcome by adding molten salt. To ensure the mechanical integrity of V2O5 electrodes, MgO is used as a binder to suppress flow of molten salt. The poor conductivity of MgO increases the resistance, and leads to rapid attenuation of the voltage. Hence, we design a hierarchical V2O5/molten salt cathode with binder-free MgO by using a novel liquid mixing method. The molten salt is anchored on the interspace of hierarchical V2O5 with structured confinement effects. Cathodes synthesized with 20 wt.% of molten salt exhibit a short active time and high specific energy. To further improve electronic conductivity, 10 wt.% Ni is added into the aforementioned cathodes. The optimum specific capacity (255.80 mAh g−1) and specific energy (559.74 Wh Kg−1) can be obtained with 0.1 A cm−2 at 500 °C and a cut-off voltage of 1.6 V. Excellent discharge performance is achieved because of the low resistance (high Li+ diffusion and well-organized electron transport path), good mechanical integrity, and complete chemical reaction. This strategy provides a new way to regulate the conductivity of binder-free solid-state batteries.