<i>Anti</i>-Perovskite Li-Battery Cathode Materials

Through single-step solid-state reactions,
a series of novel bichalcogenides
with the general composition (Li2Fe)ChO (Ch = S, Se, Te) are successfully synthesized.
(Li2Fe)ChO (Ch = S, Se)
possess cubic anti-perovskite crystal structures,
where Fe and Li are completely disordered on a common crystallographic
site (3c). According to Goldschmidt calculations,
Li+ and Fe2+ are too small for their common
atomic position and exhibit large thermal displacements in the crystal
structure models, implying high cation mobility. Both compounds (Li2Fe)ChO (Ch = S, Se) were
tested as cathode materials against graphite anodes (single cells);
They perform outstandingly at very high charge rates (270 mA g–1, 80 cycles) and, at a charge rate of 30 mA g–1, exhibit charge capacities of about 120 mA h g–1. Compared to highly optimized Li1–xCoO2 cathode materials, these novel anti-perovskites are easily produced at cost reductions
by up to 95% and, yet, possess a relative specific charge capacity
of 75%. Moreover, these iron-based anti-perovskites
are comparatively friendly to the environment and (Li2Fe)ChO (Ch = S, Se) melt congruently; the
latter is advantageous for manufacturing pure materials in large amounts.