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.