High-Temperature Inorganic Ionic Thermoelectrics Enabled by an Oxygen-Mediated Operational Mode.

Thermoelectric technology holds great promise for converting heat into electricity. In this work, we propose an "oxygen-mediated" ion thermoelectric (i-TE) operational mode in which a high-temperature-activated, defect-containing inorganic i-TE material captures O2- flux from the external environment to enable high-power output at elevated temperatures. In this mode, the thermodiffusion of oxygen ions forms an ionic current, while the "zero-cost" O2 in ambient air supplies an inexhaustible source of O2- to the circuit to support load power generation. A thermopower of 17.83 mV·K-1 was achieved, which was further enhanced to 20.52 mV·K-1 under the oxygen-sufficient condition, with a figure of merit ZTi reaching 1.43. The in-situ characterization confirms the dynamic filling behavior of oxygen defect-recovery in the lattice. A module composed of nine units achieves a maximum open-circuit voltage of 3.53 V and a maximum output power of approximately 1.47 mW under a 20 K temperature difference, and maintains stable output for more than 24 h, surpassing most reported electronic and ionic thermoelectric materials. This oxygen-mediated concept unlocks high-power ionic thermoelectric output at elevated temperatures and extends the potential application scope of ionic thermoelectrics toward high-temperature thermoelectric energy conversion and sensing in oxygen-containing environments.