Low-Cost Layered K0.45Mn0.9Mg0.1O2 as a High-Performance Cathode Material for K-Ion Batteries

Novel, potassium-deficient, layered P3-K0.45Mn0.9Mg0.1O2 is successfully prepared through a simple solid-state reaction method; its electrochemical performance as a cathode material for K-ion batteries is explored for the first time. The as-prepared K0.45Mn0.9Mg0.1O2 delivers a high reversible capacity of 108 mAhg 1 at a current density of 20 mAg(-1) in the potential region from 1.5 to 4.0 V. Moreover, the cyclability is enhanced by Mg substitution. After 100 cycles, the capacity of K0.45Mn0.9Mg0.1O2 can remain at about 80.8 mAhg(-1) at 20 mAg(-1). It also presents an excellent rate performance of 69.8 mAhg(-1) even at a high current density of 200 mAg(-1). Furthermore, the potassium storage mechanism is studied by using the ex situ XRD technique. These results contribute to the development of rechargeable K-ion batteries based on earthabundant elements.