Electrospun Hybrid Vanadium Oxide/Carbon Fiber Mats for Lithium- and Sodium-Ion Battery Electrodes

Abstract

Vanadium oxide nanostructures are constantly being researched and developed for cathodes in lithium- and sodium-ion batteries. To improve the internal resistance and the discharge capacity, this study explores the synthesis and characterization of continuous one-dimensional hybrid nanostructures. Starting from a sol–gel synthesis, followed by electrospinning and controlled thermal treatment, we obtained hybrid fibers consisting of metal oxide crystals (orthorhombic V2O5 and monoclinic VO2) engulfed in conductive carbon. For use as Li-ion battery cathode, a higher amount of carbon yields a more stable performance and an improved capacity. Monoclinic VO2/C fibers present a specific capacity of 269 mAh·gVOx–1 and maintain 66% of the initial capacity at a rate of 0.5 A·g–1. Orthorhombic V2O5/C presents a higher specific capacity of 316 mAh·gVOx–1, but a more limited lithium diffusion, leading to a less favorable rate handling. Tested as cathodes for Na-ion batteries, we confirmed the importance of a conductive carbon network and nanostructures for improved electrochemical performance. Orthorhombic V2O5/C hybrid fibers presented very low specific capacity while monoclinic VO2/C fibers presented an improved specific capacity and rate performance with a capacity of 126 mAh·gVOx–1.