Lithium Imide (Li₂NH) as a Solid-State Electrolyte for Electrochemical Energy Storage Applications

Abstract

We here report the prospect of lithium imide, Li2NH, as a solid-state electrolyte for the rechargeable Li-ion battery. Our study reveals that the ionic conductivity in Li2NH is greatly improved by the cation and anion ordering, which is a gradual process that is initiated by Li-filling in the LiNH2 lattice (forming nonstoichiometric Li1+xNH2−x) and sequentially forms the orthorhombic α-Li2NH (lower structural ordering) followed by the cubic β-Li2NH (higher structural ordering). The process, thus, enables synchronization between the cation and anion dynamics in β-Li2NH making this Li2NH phase as one of the fastest Li-ion conducting lightweight ionic alkaline hydrides. Our study also indicates high electrochemical stability for the Li/Li2NH interface in β-Li2NH contradicting the existing perception. The study may aid the existing research in developing a cost-effective commercial Li superionic conductor with high electrochemical and thermal stabilities and high energy density at room- to moderate-temperature.