Hollow sphere structured V2O3@C as an anode material for high capacity potassium-ion batteries

Vanadium oxides with various compositions have been reported as electrodes for potassium-ion batteries, but the poor conductivity is a main obstacle to fulfill the energy storage requirements. In this study, we synthesize a carbon-coated V2O3 hollow spheres (HS-V2O3@C) by a facile solvothermal reaction. The HS-V2O3@C electrode exhibits promising cycling stability and rate performances. It retains a high reversible capacity of 330 mA h g-1 at 100 mA g-1 after 500 cycles. Its capacity reaches 79 mA h g-1 at a high current density of 5000 mA g-1. The superior performances are mainly due to the homogeneous carbon coating layer that greatly improves the electronic conductivity and the hollow structure that buffers the volume change during the cycling. By means of ex situ X-ray diffraction and cyclic voltammetry, the mechanism of potassium ions storage in this HS-V2O3@C electrode is determined as the combination of intercalation and pseudocapacitive effects.