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

Abstract

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 MgH2 and Mg2NiH4 that are uniformly space-confined by inactive Nd2H5 frameworks with high Li-ion and electron conductivity through facile hydrogenation of single-phase Nd4Mg80Ni8 alloys. The formation of MgH2 and Mg2NiH4 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 Nd2H5 based on a molecular level could effectively alleviate the volume expansion and phase separation of thus-confined MgH2 and Mg2NiH4. More importantly, it is theoretically and experimentally verified that the uniform distribution of Nd2H5, which is an electronic conductor with a Li-ion diffusion barrier that is much lower than that of MgH2 and Mg2NiH4, could further facilitate the electron and Li-ion transfer of MgH2 and Mg2NiH4. Consequently, the space-confined MgH2 and Mg2NiH4 deliver a reversible capacity of 997 mAh g-1 at 2038 mA g-1 after 100 cycles.