Ball-milled Li3N. Commercial lithium nitride powder (99%, Strem) was ball-milled using a SPEX-8000 mill for 120 minutes under argon. Tungsten carbide vial and balls were utilized as milling media, and the ball-to-powder ratio was 16:1. All sample loading and unloading processes were handled in a glove box filled with argon to avoid oxidation. Safety note: Metal hydrides are highly reactive and may ignite spontaneously on contact with water, air, protic solvents or a moist atmosphere.