Investigation of Potassium Storage in Layered P3-Type K0.5MnO2 Cathode

Novel and low-cost batteries are of considerable interest for application in large-scale energy storage systems, for which the cost per cycle becomes critical. Here, this study proposes K_0.5MnO₂ as a potential cathode material for K-ion batteries as an alternative to Li technology. K_0.5MnO₂ has a P3-type layered structure and delivers a reversible specific capacity of ≈100 mAh g⁻¹ with good capacity retention. In situ X-ray diffraction analysis reveals that the material undergoes a reversible phase transition upon K extraction and insertion. In addition, first-principles calculations indicate that this phase transition is driven by the relative phase stability of different oxygen stackings with respect to the K content.

K-intercalation in P3-structured K_0.5MnO₂ is demonstrated for the first time. K-intercalation chemistry upon K extraction and insertion isi investigated using in situ X-ray diffraction combined with electrochemical titration and first-principles calculations. Finally, phase transitions driven by the relative phase stability of difference stacking with respect to the K content are observed.

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