Vanadium pentoxide (V2O5) is an attractive cathode material for lithium-ion batteries (LIBs) because of its low cost, high abundance, and relatively high theoretical capacity (294 mA h g (1) with two lithium insertions/extractions per unit formula at 2.0-4.0 V). However, practical applications of V2O5 are hampered by its poor structural stability, low electrical conductivity, and slow ion diffusion kinetics, resulting in poor long-term cycling stability and rate performance. In this study, V2O5 nanoparticles are synthesized by a fast sol-gel method with citric acid (C6H8O7) at 400, 500, 600, and 700 degrees C. The thickness of the amorphous layers on the surface of the V2O5 nanoparticles is controlled from approximately 4-5 to 1-2 nm by adjusting the calcination temperature. The V2O5 nanoparticles synthesized at 600 degrees C show better electrochemical performances than the other samples. They exhibit a high initial discharge capacity of 276 mA h g (1) between 2.1 and 4.0 V at a rate of 1 C, and good capacity retention of 83% after 50 cycles. Even at 10 C rate, a discharge capacity of about 168 mA h g (1) is obtained after 100 cycles. The excellent rate capability and cycling stability are also achieved at current densities of 0.5-20 C. (C) 2015 Elsevier Ltd. All rights reserved.