Thermally chargeable supercapacitor working in a homogeneous, changing temperature field

A thermally chargeable supercapacitor (TCS) system is developed to harvest electrical energy from a uniform temperature field of a changing low-grade heat source. Without any temperature gradient, the TCS absorbs heat when temperature rises and releases electricity during discharging. As temperature decreases, the system configuration returns to the initial condition, so that the thermal-to-electrical energy conversion can be continuously conducted. With a nickel-coated carbon nanotube or nanoporous carbon-based electrode, the thermal sensitivity and the electrode surface area are enhanced simultaneously, leading to a high output voltage around 100–160 mV and a high specific energy of 600–1800 mJ per gram of electrode material in each thermal cycle, with a mild temperature range of ~50 °C.