6533b853fe1ef96bd12aca0a

RESEARCH PRODUCT

Atomistic Modeling of a New Storage

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description

It was observed that Me/Li2O and Me/LiF nanocomposites (Me is a metal that does not alloy with lithium) are able to exhibit an extra Li storage typically beyond the uptake of stoichiometric Li in the potential window 1.2 0.02 V, with pseudo-capacitive behavior and high-rate performance. Among the composites, the Ru/Li2O exhibits a high extra Li storage at this low potential. Moreover, the Li2O matrix allows one a higher storage in contact with transition metal than the LiF matrix [1,2]. To clarify the mechanism of the Li interfacial storage anomaly, we have performed comparative first principles calculations on the atomic and electronic structure of polar Ti/Li2O(111) and nonpolar Cu/LiF(001) interfaces with extra lithium atoms inserted inside both 2D interfaces [3]. Unlike pure LiX and transition metal bulk, a Me/LiX interface saturated with extra lithium can store one (LiF) or two-three (Li2O) monolayers of inserted Li(per interface Li ions) with electrons being transferred largely to transition metal surface, in agreement with the mechanism proposed recently [4]. While LiX surface layers or interfacial core serve as hosts for extra Li, adatoms of transition metal serve as the electron sinks, depending on its electronegativity. Fast diffusion of the extra Li along the Me/LiX interface results from its heterogeneity: Li ions are moving along the LiX interfacial plane while an electron takes the metal path. In more general terms, the present study corroborates that the stoichiometry of nanoparticlesand nanocomposites could markedly differ from the bulk phases. This phenomenon provides a bridge between an electrostatic capacitor and an electrode storage and might combine advantages of both situations.