In operando study of orthorhombic V2O5 as positive electrode materials for K-ion batteries

Y Herein, the electrochemical performance and the mechanism of potassium insertion/deinsertion in orthorhombic V2O5 nanoparticles are studied. The V2O5 electrode displays an initial potassiation/depotassiation capacity of 200 mAh g(-1)/217 mAh g(-1) in the voltage range 1.5-4.0 V vs. K+/K at C/12 rate, suggesting fast kinetics for potassium insertion/deinsertion. However, the capacity quickly fades during cycling, reaching 54 mAh g(-1) at the 31st cycle. Afterwards, the capacity slowly increases up to 80 mAh g(-1) at the 200th cycle. The storage mechanism upon K ions insertion into V2O5 is elucidated. In operando synchrotron diffraction reveals that V2O5 first undergoes a solid solution to form K0.6V2O5 phase and then, upon further K ions insertion, it reveals coexistence of a solid solution and a two-phase reaction. During K ions deinsertion, the coexistence of solid solution and the two-phase reaction is identified together with an irreversible process. In operando XAS confirms the reduction/oxidation of vanadium during the K insertion/extraction with some irreversible contributions. This is consistent with the results obtained from synchrotron diffraction, ex situ Raman, X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). Moreover, ex situ XPS confirms the cathode electrolyte interphase (CEI) formation on the electrode and the decomposition of CEI film during cycling. (C) 2021 The Authors. Published by ELSEVIER B.V. and Science Press on behalf of Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences.

Automated summary

The electrochemical performance and mechanism of potassium insertion/deinsertion in orthorhombic V2O5 nanoparticles were studied. The V2O5 electrode exhibited fast kinetics for potassium insertion/deinsertion with an initial capacity of 200 mAh g(-1)/217 mAh g(-1 but quickly faded during cycling, gradually increasing towards the 200th cycle. The storage mechanism involved solid solution formation and a two-phase reaction upon potassium ions insertion, with some irreversible contributions observed during potassium deinsertion.