Layered K_0.37MnO₂·0.25H₂O as cathode material for potassium ion batteries

Lithium supply shortages have prompted the search for alternatives to widespread grid system applications. Potassium-ion batteries (PIBs) have emerged to promising candidates for this purpose. Nonetheless, the large radius of K⁺(1.38 Å) impedes the march of satisfactory cathode materials. Here, we used solid-phase synthesis to prepare a layered K_0.37MnO₂·0.25H₂O (KMO) cathode, comprising alternately connected MnO₆octahedra with a large interlayer spacing (0.71 nm) to accommodate the migration and transport of K⁺ions. The cathode material achieved initial specific capacities of 102.3 and 88.1 mA h g^-1at current densities of 60 mA g^-1and 1 A g^-1, respectively. The storage mechanism of K⁺ions in PIBs was demonstratedex situusing x-ray diffraction, x-ray photoelectron spectroscopy, and Raman spectroscopy measurements. Overall, our proposed KMO was confirmed as an auspicious cathode material for potential use in PIBs.