Giant yet robust barocaloric cooling in superionic-ductile Ag2S thermoelectrics

Solid-state cooling based on caloric effects offers a promising and sustainable refrigeration solution. However, developing barocaloric materials that combine a large thermal response with high mechanical ductility remains challenging. Here, we report a giant barocaloric effect in superionic-ductile Ag2S-based thermoelectric semiconductors, achieved through medium-entropy alloying (Ag2S1-x-ySexTey). This yields a colossal barocaloric strength of ~0.41 J kg-1 K-1 MPa-1 near room temperature, enabled by a large entropy change (~42 J kg-1 K-1) under a low driving pressure of ~100 MPa. In-situ neutron and X-ray diffraction reveal a reversible pressure-driven order-disorder transition of the Ag-ion sublattice, with diffuse scattering confirming the giant configurational entropy change. Simultaneously, the material's inherently exceptional plasticity (compression >90%, stretching ~43%, bending >100%) ensures excellent cyclability, with a stable adiabatic temperature change of ~4.8 K and negligible performance drift during repeated cycling. This work synergizes mechanical ductility with superionic entropy engineering, establishing a robust platform for efficient, durable barocaloric cooling and expanding the functional scope of thermoelectrics as versatile solid-state refrigerants.