Layered K 0.37 MnO 2 ·0.25H 2 O 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 0.37 MnO 2 ·0.25H 2 O (KMO) cathode, comprising alternately connected MnO 6 octahedra with a large interlayer spacing (0.64 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 -1 at current densities of 60 mA g -1 and 1 A g -1 , respectively. The storage mechanism of K + ions in PIBs was demonstrated ex situ using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy measurements. Overall, our proposed KMO was confirmed as an auspicious cathode material for potential use in PIBs.