Ultrahigh Potassium Storage Capacity of Ca₂Si Monolayer with Orderly Multilayered Growth Mechanism

Abstract

As the rising renewable energy demands and lithium scarcity, developing high‐capacity anode materials to improve the energy density of potassium‐based batteries (PBBs) is increasingly crucial. In this work, a unique orderly multilayered growth (OMLG) mechanism on a 2D‐Ca2Si monolayer is theoretically demonstrated for potassium storage by first‐principles calculations. The global‐energy‐minimum Ca2Si monolayer is a semiconductor with isotropic mechanical properties and remarkable electrochemical properties, such as a low potassium ion migration energy barrier of 0.07 eV and a low open circuit voltage ranging from 0.224 to 0.003 V. Most notably, 2D‐Ca2Si demonstrates an ultrahigh theoretical specific capacity of 5459 mAh g−1 and a total specific capacity of 610 mAh g−1, reaching up to 89% of the capacity of a potassium metal anode. Remarkably, the OMLG mechanism facilitates stable, dendrite‐free deposition of hcp‐K metal layers on the 2D‐Ca2Si surface, where the ultrahigh and gradually converging lattice match as the layers increase is the key to achieving theoretically near‐infinite growth. The study theoretically demonstrates the Ca2Si monolayer a highly promising anode material, and offers a novel potassium storage strategy for designing 2D anode materials with high specific capacity, rapid potassium‐ion migration, and good safety.

Prediction of Halogenated MXenes as Electrode Materials for Halide-Ion Batteries

“…However, their large-scale application is limited by the scarcity and high cost of natural lithium resources . Therefore, alternative cationic batteries, such as Na + , K + , Mg 2+ , Ca 2+ , Zn 2+ , and Al 3+ , have attracted considerable attention as potential substitutes and supplements for LIBs. − In comparison to the thriving development of metal cation batteries, rechargeable batteries based on anions as the active material are still in their nascent stages of investigation. Among them, the alkaline battery and nickel metal hydride battery using OH – as the charge carrier have been studied most extensively. , Notably, in halide ions, F – and Cl – exhibit exceptional attributes, such as high energy density, lightweightness, high electronegativity, excellent stability, and observable natural reserves with easy accessibility, thereby rendering them highly suitable as active materials in rechargeable batteries. − …”