Confined phase transition triggering high-performance energy storage thermo-battery

Abstract

A thermoelectric device can directly convert heat to electricity, but its operation requires a temperature difference between the two electrodes of the thermocell. Unfortunately, the potential difference between the two electrodes disappears when there is no the temperature difference, which greatly limits the practical conditions to power electronic devices. Here, we first report the utilization of the thermo-responsive hydrophobic interaction to obtain a high-performance thermo-battery with a certain electrical storage capacity, and achieve a thermoelectric device that can still supply power in the absence of heat input. In I−/I3− aqueous solution containing methyl cellulose (MC), the I3− concentration gradient caused by the hydrophobic association effect and the low/high entropy electrolyte transition caused by the confinement of bacterial cellulose (BC) not only promoted the thermo-battery to have high thermoelectric performance (1.75 and ‒6.84 mV K‒1), but most surprisingly, the thermal voltage can be slowly self-discharged for about 312 hours (from ‒164.4 to ‒29.0 mV) when the temperatures at the hot- and cold-terminal electrodes are almost the equal. This is the first discovery of rechargeable battery behavior in the field of thermoelectricity, which opens up a new development of thermocells at a deeper level.