Abnormal Freezing Effect on Electron Conduction of Ball‐milled Lanthanum Trihydride for Superionic Conductor

Abstract A recent finding shows that lattice deformation could transform the mixed electronic/hydride (H − ) conducting lanthanum trihydride (LaH 3 ) to a superionic H − conductor. Such a feature would enable the development of a brand‐new all‐solid‐state hydride ion battery. It is essential to elucidate the mechanism of such a phenomenon. Here, we disclose an abnormal freezing effect on the electronic conductivity ( σ e ) of the ball‐milled LaH 3 ; that is, σ e can be lowered by over 2 orders of magnitude upon a low‐temperature treatment. Low‐temperature Raman reveals that at low temperatures, lattice deformation has a noticeable influence on the interaction of hydrogen at octahedral (H o ) and tetrahedral (H t ) sites, which may play a crucial role in hindering electron conduction. This freezing effect can significantly improve the ionic transfer number of rare earth‐based H − conductors and provide a new direction to the development of solid electrolytes for low‐temperature all‐solid‐state batteries.