Preparation of Li-Excess and Li-Deficient Antiperovskite Structured Li 2+ x OH 1- x Br and Their Effects on Total Ionic Conductivity.

This paper describes about the effect of Li-H exchange amount on total lithium-ion (Li + ) conductivity of Li 2+ x OH 1- x Br ( x = -0.5 to +0.4). These samples are systematically prepared at room temperature by a dry ball-milling process using LiOH, LiOH·H 2 O, Li 2 O, and LiBr as starting materials. Synchrotron X-ray diffraction analysis reveals that single-phase Li 2+ x OH 1- x Br samples are formed within x = -0.5 to +0.35. For improving total Li + conductivity (σ t ), a larger x value increases both the Li carrier density and lattice constant as positive factors, while that decreases both the crystallite size and OH rotational unit possibly assisting Li + conduction as negative factors. This trade-off provides an optimized σ t of 3.6 × 10 -6 S cm -1 at the Li-excess Li 2.2 OH 0.8 Br composition, which is ca. 3 times higher than pristine Li 2 OHBr (1.1 × 10 -6 S cm -1 ). The hydrogen incorporation into the lattice is confirmed by neutron diffraction analysis, and the refined composition is almost consistent with the prepared composition.