Synergism of Rare Earth Trihydrides and Graphite in Lithium Storage: Evidence of Hydrogen‐Enhanced Lithiation

The lithium storage capacity of graphite can be significantly promoted by rare earth trihydrides (REH 3 , RE = Y, La, and Gd) through a synergetic mechanism. High reversible capacity of 720 mA h g −1 after 250 cycles is achieved in YH 3 –graphite nanocomposite, far exceeding the total contribution from the individual components and the effect of ball milling. Comparative study on LaH 3 –graphite and GdH 3 –graphite composites suggests that the enhancement factor is 3.1–3.4 Li per active H in REH 3 , almost independent of the RE metal, which is evident of a hydrogen‐enhanced lithium storage mechanism. Theoretical calculation suggests that the active H from REH 3 can enhance the Li + binding to the graphene layer by introducing negatively charged sites, leading to energetically favorable lithiation up to a composition Li 5 C 16 H instead of LiC 6 for conventional graphite anode.