Understanding the Predominant Potassium-Ion Intercalation Mechanism of Single-Phased Bimetal Oxides by <i>in Situ</i> Magnetometry
Zhongchen Zhao, Hao Zhang, Fei Li, Linyi Zhao, Qiang Li, Hongsen Li
Abstract
The electrochemical performance of electrode materials is largely dependent on the structural and chemical evolutions during the charge–discharge processes. Hence, revealing ion storage chemistry could enlighten mechanistic understanding and offer guidance for rational design for energy storage materials. Here, we investigate the mechanisms of potassium (K)-ion storage in the promising bimetal oxide materials by in situ magnetometry. We focus on a single-phased hollow FeTiO3 (SPH-FTO) hexagonal prism synthesized through a complexing-reagent assisted approach and find that the K-ion storage in this compound occurs predominantly with an intercalation mechanism and fractionally a conversion mechanism. We also demonstrate a K-ion hybrid capacitor assembled with the prepared SPH-FTO hexagonal prism anode and activated carbon cathode, delivering a high energy density and high power density as well as extraordinary cycling stability. This new understanding is used to showcase the inherently high K-ion storage properties from the earth-abundant FeTiO3.