K₃MnO₄: A New Cathode Material for K-Ion Batteries

In the search for materials used as active species incathodesfor K-ion batteries, only a few compositions of transition metal oxidesor transition metal polyanionic frameworks have been proposed so far.In this work, we report for the first time the synthesis and studyof the electrochemical activity an original K3MnO4 polymorph. This phase is a 0D-type structure made of isolated MnO4 tetrahedra surrounded by K+ ions. A reversiblecharge capacity of almost one K+ per unit formula at theaverage voltage of 2.3 V vs K+/K is obtained, leading tothe reversible formation of K2MnO4 through abiphasic process.