Objectives: Progress in improving the performance characteristics of lithium-ion batteries is largely determined by the cathode material. Various modifications of vanadium oxides attract interest as cathode materials. For example, a vanadium ion or a vacancy at a vanadium pentoxide lattice site can accommodate two positively charged lithium ions, resulting in a high theoretical specific capacity (~294 mAh·g–1). However, during operation, the material rapidly degrades and loses its initial specific capacity. A variety of strategies has been proposed to mitigate capacity degradation, including structural modification, phase composition control, and heteroatom doping with foreign metal ions. The main aim of this work was to evaluate the effect of the phase composition of cathode material based on vanadium oxide nanofibers on the performance characteristics of a lithium-ion battery. Experimental: The cathode material was fabricated from vanadium oxide nanofibers synthesized via electrospinning. The phase composition and surface morphology of the nanofibers were studied by X-ray diffraction and scanning electron microscopy. The cathode material was evaluated using standard electrochemical techniques. Conclusions: All samples were mixtures of vanadium oxides (V2O5, VO2, V4O9, V6O13) in various ratios. With increasing molar fraction of oxalic acid during annealing, the percentage of vanadium pentoxide decreases while that of vanadium dioxide increases. Electrochemical studies of the material showed that replacement of vanadium pentoxide nanofibers in the cathode material with nanofibers consisting of a mixture of vanadium oxides led to a decrease in initial specific capacity and did not increase cycling stability.