Deforming lanthanum trihydride for superionic conduction.

With strong reducibility and high redox potential, the hydride ion (H) is a reactive hydrogen species and an energy carrier. Materials that conduct pure H at ambient conditions will be enablers of advanced clean energy storage and electrochemical conversion technologies. However, rare earth trihydrides, known for fast H migration, also exhibit detrimental electronic conductivity. Here we show that by creating nanosized grains and defects in the lattice, the electronic conductivity of LaH can be suppressed by more than five orders of magnitude. This transforms LaH to a superionic conductor at -40 °C with a record high H conductivity of 1.0 × 10 S cm and a low diffusion barrier of 0.12 eV. A room-temperature all-solid-state hydride cell is demonstrated.