Prepotassiated V2O5 as the Cathode Material for High-Voltage Potassium-Ion Batteries

摘要

The voltage and capacity of cathodes are critical factors for energy density of batteries. However, the cutoff voltage of cathode materials in potassium-ion batteries (PIBs) is usually 4.0V, causing structural transformations in the electrode materials in the course of repeated insertion/extraction of K+ ions with a large radius (1.38 angstrom). Materials with large interlayer spacing and short ion diffusion paths show promise to overcome this issue. K0.486V2O5 nanobelts, prepared by preinserting K+ ions into V2O5, are used as cathode materials in high-voltage PIBs. Various analysis methods are used to understand the insertion/extraction behavior of K+ ions in K0.486V2O5 cathodes cycled between 1.5 and 4.2V. The analyses reveal the highly reversible structural evolution of K0.486V2O5, in which the chemically inserted K+ ions partially remain between VO layers charged at high voltage serving as stabilizing species to prevent phase transformations. K0.486V2O5 cathodes exhibit a high specific capacity of 159mAhg(-1) at 20mAg(-1) with good cycling stability of 67.4% after 100 cycles at 100mAhg(-1) in the half K-ion cell. The results provide guidelines for designing layered transition metal oxides to be used as cathode materials for high-voltage PIBs with high energy density.