Language：English   Publisher：Nature Materials  

Advances in electrochemical devices have been primarily driven by the discovery and development of electrolyte materials. Yet the development of high-performance and chemically stable proton-conducting oxide electrolytes remains a challenge due to proton trapping and the resulting trade-offs between ionic carrier concentration and conductivity in doped oxides. Here we demonstrate that cubic perovskite oxides with heavy Sc doping can overcome these limitations. BaSn<inf>0.3</inf>Sc<inf>0.7</inf>O<inf>3–δ</inf> and BaTi<inf>0.2</inf>Sc<inf>0.8</inf>O<inf>3–δ</inf> are found to exceed the technological threshold of a total proton conductivity of 0.01 S cm⁻¹ for fuel cell electrolytes at 300 °C. The structural stability of BaSn<inf>0.3</inf>Sc<inf>0.7</inf>O<inf>3–δ</inf> is further validated under harsh chemical and fuel cell conditions. Molecular dynamics simulations using a machine learning force field illustrate rapid proton diffusion pathways along the ScO<inf>6</inf> octahedral network, effectively mitigating proton trapping, while protons are preferentially associated with Sc. Lattice softness is proposed as a primary design descriptor for increasing Sc content in perovskite oxides and developing high-performance electrolytes for electrochemical devices.

DOI： 10.1038/s41563-025-02311-w

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