K₃MnO₄: A New Cathode Material for K-Ion Batteries

Abstract

In the search for materials used as active species in cathodes for K-ion batteries, only a few compositions of transition metal oxides or transition metal polyanionic frameworks have been proposed so far. In this work, we report for the first time the synthesis and study of the electrochemical activity an original K 3 MnO 4 polymorph. This phase is a 0D-type structure made of isolated MnO 4 tetrahedra surrounded by K + ions. A reversible charge capacity of almost one K + per unit formula at the average voltage of 2.3 V vs K + /K is obtained, leading to the reversible formation of K 2 MnO 4 through a biphasic process.

Advancements in cathode materials for potassium-ion batteries: current landscape, obstacles, and prospects

“…, KCrO 2 232 and KCrS 2 231 ) or potassium-rich layered oxides, as found in, for instance, the aforementioned honeycomb layered oxide compositions or potassium hypomanganates such as K 3 MnO 4 . 273 Another strategy involves exploring materials that operate through the combined participation of both transition metal cation and oxygen/sulphide anion redox chemistry, enabling the full utilisation of the capacity in both potassium-rich and potassium-deficient layered oxide cathode materials. It is noteworthy that reversible anion-redox chemistry has been observed in certain layered oxide cathode materials, such as K 0.4 Fe 0.5 Mn 0.5 O 2 238 and K 0.78 Fe 1.60 S 2 .…”