Selective Lattice Doping Enables a Low‐Cost, High‐Capacity and Long‐Lasting Potassium Layered Oxide Cathode for Potassium and Sodium Storage

Abstract

Layered transition metal oxides are highly promising host materials for K ions, owing to their high theoretical capacities and appropriate operational potentials. To address the intrinsic issues of KxMnO2 cathodes and optimize their electrochemical properties, a novel P3‐type oxide doped with carefully chosen cost‐effective, electrochemically active and multi‐functional elements is proposed, namely K0.57Cu0.1Fe0.1Mn0.8O2. Compared to the pristine K0.56MnO2, its reversible specific is increased from 104 to 135 mAh g‐1. In addition, the Cu and Fe co‐doping triples the capacity under high current densities, and contributes to long‐term stability over 500 cycles with a capacity retention of 68%. Such endeavor holds the potential to make potassium‐ion batteries particularly competitive for application in sustainable, low‐cost, and large‐scale energy storage devices. In addition, the cathode is also extended for sodium storage. Facilitated by the interlayer K ions that protect the layered structure from collapsing and expand the diffusion pathway for sodium ions, the cathode shows a high reversible capacity of 144 mAh g‐1, fast kinetics and a long lifespan over 1000 cycles. The findings offer a novel pathway for the development of high‐performance and cost‐effective sodium‐ion batteries.