High-temperature supercapacitors with enhanced charge transportation and capacitances are promising to meet specific requirements for underhood automotive component, oil drilling, military and space applications. However, state-of-the-art supercapacitors are always operated at room temperature due to the thermal instability of the hydrous electrolytes and organic separators. Herein, we present the fabrication of a high-temperature supercapacitor tailored by a ceramic NiO/ZrO2 separator. This supercapacitor has a working temperature up to 140 degrees C, a capacitance of 342 F g(-1) at current density of 2 A g(-1) and good cycling stability over 2000 cycles. The experimental realization of physical proof-of-concept high-temperature supercapacitors may provide new opportunities for markedly improving the capacity of energy storage systems.