Enhancing Conversion Efficiency and Storage Capacity of a Thermally Self‐Chargeable Supercapacitor

Waste heat utilization, including solar heat and various industrial waste heats, plays an important role in improving energy efficiency, but current heat-to-electricity conversion technologies can only harvest a little heat energy. A new direct thermally self-chargeable supercapacitor (TCS) system, using the nanoporous carbon electrode in electrolyte mixed with nanoparticles, can simultaneously produce and store electric energy from a low-grade heat source. Moreover, it can simultaneously realize charging and discharging processes. A method of strengthening ions migration by adding nanoparticles into electrolytes is proposed. When heated, due to the Brownian motion of suspended nanoparticles and the interactions among ions and nanoparticles, more ions migrate to the hot electrode, which leads to a high thermal-induced open-circuit voltage (OCV) of 265 mV, under a mild temperature difference of 50 K. This new type of TCS system attains a thermoelectric coefficient of 5.3 mV K(-1)and outperforms other conventional TCS systems in which liquid electrolytes are involved.