We report in the context of lithium-rich antiperovskite cathode materials
outstanding electrochemical properties of (Li2Fe)SeO, which
for the first time was synthesized via direct ball-milling. The unique
structured material displays a electrochemical cycling performance of
250 mAh g−1 at 0.1 C when used as a cathode in lithium-ion batteries.
Comprehensive electrochemical analysis combined with detailed
transmission electron microscopy studies reveal that, above 2.5 V, the
multi electron storage mechanism involves conversion of (Li2Fe)SeO to
Fe1−?Se?. Our results furthermore demonstrate the general relevance
of our findings to the whole class of antiperovskite cathode materials
and present a route to strongly enhance their cell performance by
avoiding the degradation path deciphered by our studies.