Remarkable ionic thermoelectric performance of high-entropy gel thermocell near room temperature†

Abstract

Gel thermocell, as a green and clean energy conversion technology, has a high ionic thermopower, and it is capable of functioning for self-powered sensors near room temperature. However, ionic thermoelectric performance is currently limited and needs to be improved to meet the practical requirements. To date, it has been a major challenge to significantly improve performance, including ionic thermopower, output power density, and energy harvesting. Herein, we propose a “high-entropy” concept by controlling the gel compositions to achieve remarkable ionic thermoelectric performance. The high-entropy results from multi-ion coupling, especially for anions, to improve redox reaction entropy change, exchange current density, and ionic conductivity, pushing the performance to high levels. The fabricated high-entropy gel thermocell showed an ionic thermopower of 31 mV K⁻¹, a normalized maximum output power density of 11.4 mW m⁻² K⁻², and a one-hour continuous discharge energy density of 4.3 J m⁻² K⁻². Moreover, a device assembled by twelve thermocells delivered a maximum output power density of 2.0 mW m⁻² K⁻². Thus, the strategy proposed in this work provides guidelines for designing other high-performance gels.