Discharge behavior of NiO as thermal battery cathode at ultrahigh temperature

[Display omitted] •The thermal decomposition temperature of NiO exceeds 1980℃.•The specific capacity of Li-B/NiO thermal battery is 642 mAh g−1 at 500℃.•The actual utilization for NiO cathodes can reach 89.4% of the theoretical capacity.•Even at 700℃, the specific capacity of NiO cathodes is 243 mAh g−1. Thermal batteries are high-temperature lithium metal batteries. The thermal stability and the specific capacity of cathode materials are key factors to its application. In this case, NiO with high decomposition temperature and theoretical capacity was constructed as a thermal battery cathode. At 500℃, the specific capacity of NiO cathode was about 642 mAh g−1 with a large current density of 0.1 A cm−2 and a cut-off voltage of 1.0 V. This capacity reached 89.4% of the theoretical value at those harsh discharge conditions. As the discharge temperature increased to 700℃, an obvious discharge voltage platform of 1.5 V and a specific capacity of 243 mAh g−1 were still observed for NiO cathodes. While thermal batteries using other common cathode materials cannot discharge efficiently at 700 °C. The XRD and TEM indicated that the high-temperature reaction of the NiO cathode was a one-step reaction: NiO + 2Li++2e-→ Ni + Li2O. This ultra-high temperature discharge ability suggests the NiO cathode can be very promising in high-capacity and long-life thermal battery applications.