Selective Regulation of Electron–Ion–Phonon Transport in Thermoelectric Materials toward High Performance and Stability

The complex inter-relationships among electrons, ions, and phonons make it extremely challenging to simultaneously regulate these microscopic particles. Superionic conductors offer an ideal operating platform but are often limited by their inherent ion mobility and susceptibility to degradation under extreme conditions. We developed a strategy to improve the stability of ion-conducting thermoelectric materials by constructing an in situ ligand-derived organic–inorganic interface. This strategy selectively enhances the electrical conductivity while suppressing the ionic and thermal conductivity. The resulting materials are classified as phonon liquid electron crystal ionic insulators (PLECII). The PLECII effectively prevents the accumulation of "liquid-like" ions under conditions of high current density and elevated temperature. Additionally, this strategy decouples the transport of electrons, ions, and phonons, resulting in an exceptional thermoelectric performance. Notably, a record-high energy conversion efficiency of 4.0% was achieved in the Cu2S-based device at a temperature difference of 473.1 K. Our method enables the design of materials with tunable electrical, ionic, and thermal conductivity, thereby expanding the applications of superionic conductors.