Carbon-Encapsulated Hollow Porous Vanadium-Oxide Nanofibers for Improved Lithium Storage Properties

Carbon-encapsulated hollow porous vanadium-oxide (C/HPV₂O₅) nanofibers have been fabricated using electrospinning and postcalcination. By optimized postcalcination of vanadium-nitride and carbon-nanofiber composites at 400 °C for 30 min, we synthesized a unique architecture electrode with interior void spaces and well-defined pores as well as a uniform carbon layer on the V₂O₅ nanofiber surface. The optimized C/HPV₂O₅ electrode postcalcined at 400 °C for 30 min showed improved lithium storage properties with high specific discharge capacities, excellent cycling durability (241 mA h g^-1 at 100 cycles), and improved high-rate performance (155 mA h g^-1 at 1000 mA g^-1), which is the highest performance in comparison with previously reported V₂O₅-based cathode materials. The improved electrochemical feature is due to the attractive properties of the carbon-encapsulated hollow porous structure: (I) excellent cycling durability with high specific capacity relative to the adoption of carbon encapsulation as a physical buffer layer and the effective accommodation of volume changes due to the hollow porous structure, (II) improved high-rate performance because of a shorter Li-ion diffusion pathway resulting from interior void spaces and well-defined pores at the surface. This unique electrode structure can potentially provide new cathode materials for high-performance lithium-ion batteries.