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

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 K x MnO 2 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 K 0.57 Cu 0.1 Fe 0.1 Mn 0.8 O 2 . Compared to the pristine K 0.56 MnO 2 , 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.