Reversible Sodium and Potassium-Ion Intercalation in Na0.44MnO2

Global demands drew attention towards energy production and storage technologies in the twenty-first century. Lithium-ion batteries cannot satisfy needs because of limited resources of Li. Sodium-ion batteries can be a promising alternate replacement with a redox potential E (Na+/Na) = −2.71 V vs SHE. Potassium-ion batteries have recently gained interest in competing with sodium with a redox potential of E (K+/K) = −2.93 V and has an advantage of smaller stokes radius. Herein, we tried to understand the K-insertion and de-insertion in sodium-based transition metal oxide (Na0.44MnO2). The tunnel-type Na0.44MnO2 was prepared by combustion synthesis technique which has an orthorhombic structure with a space group of Pbam. It has 3D tunnel-type structure with large and small tunnels as a path for diffusion of ions. For the first time, tunnel-type Na0.44MnO2 was investigated as K+-ion intercalation host. This study shows reversible K+-ion intercalation with an initial discharge of 74 mAh g−1 at C/20 current rate and good cycling stability up to 50 cycles.