Synergistic Effect of Composite V2O5/Ca0.17V2O5 Film Electrodes as High-Performance Cathodes of SIBs

The V2O5/Ca0.17V2O5 film electrodes on indium-doped tin oxide (ITO) conductive glasses were synthesized by a low-temperature liquid-phase deposition method and thermal treatment. The deposited film electrodes were directly used as cathodes for sodium-ion batteries without additional media. X-ray diffraction and high-resolution transmission electron microscopy results demonstrated that V2O5/Ca0.17V2O5 films were successfully formed. The ions diffusion, electrode reaction kinetics, capacity, and cyclic performance were revealed by cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge/discharge measurements. The V2O5/Ca0.17V2O5 film delivered a discharge capacity of 148.465 mAh m–2 at 1 C rate, which was larger than 100.086 mAh m–2 of the pure V2O5 film. Moreover, the V2O5/Ca0.17V2O5 film exhibited an initial discharge capacity of 144.712 mAh m–2 (90.11% retained after 100 cycles) at a 1 C rate and 112.525 mAh m–2 (103.91% retained after 100 cycles) at a 2 C rate. Encouragingly, the rate performance was worthy of mention, which indicated a good reversibility. The impressive electrochemical ability could be attributed to the synergistic effect of two phases. The ex-situ X-ray diffraction and X-ray photoelectron spectroscopy results proved that the Ca0.17V2O5 supported the stability of the structure, and the V2O5 phase acted as a host material for ions insertion/extraction. This work may provide a promising strategy for developing high-performance electrode materials.