Metal Hydrides with In Situ Built Electron/Ion Dual-Conductive Framework for Stable All-Solid-State Li-Ion Batteries.

Due to their high theoretical specific capacity, metal hydrides are considered to be one of the most promising anode material for all-solid-state Li-ion batteries. Their practical application suffers, however, from the poor cycling stability and sluggish kinetics. Herein, we report the in situ fabrication of MgH and MgNiH that are uniformly space-confined by inactive NdH frameworks with high Li-ion and electron conductivity through facile hydrogenation of single-phase NdMgNi alloys. The formation of MgH and MgNiH nanocrystals could not only shorten Li-ion and electron diffusion pathways of the whole electrode but also relieve the induced stress upon volume changes. Additionally, the robust frameworks constructed by homogeneous distribution of inactive NdH based on a molecular level could effectively alleviate the volume expansion and phase separation of thus-confined MgH and MgNiH. More importantly, it is theoretically and experimentally verified that the uniform distribution of NdH, which is an electronic conductor with a Li-ion diffusion barrier that is much lower than that of MgH and MgNiH, could further facilitate the electron and Li-ion transfer of MgH and MgNiH. Consequently, the space-confined MgH and MgNiH deliver a reversible capacity of 997 mAh g at 2038 mA g after 100 cycles.