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

ABSTRACT 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 O 2− 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” O 2 in ambient air supplies an inexhaustible source of O 2− 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 ZT i 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.