Graphene-nanosheet-wrapped LiV3O8 nanocomposites as high performance cathode materials for rechargeable lithium-ion batteries

A novel graphene-nanosheet-wrapped LiV 3 O 8 nanoflakes (GNS/LiV 3 O 8 ) nanocomposite has been generated by sheet-to-sheet self-assembly of ultrathin LiV 3 O 8 nanoflakes and graphene nanosheets. When used as a cathode material for lithium-ion batteries, the GNS/LiV 3 O 8 nanocomposites show superior rate capability and excellent cycling stability. Discharge capacities of approximately 328.7, 305.3, 276.9, 251.4, and 209.3 mAh g −1 are achieved at current densities of 2, 5, 10, 20, and 50C, respectively. A reversible capacity of approximately 287.2 mAh g −1 is retained even after 100 cycles at 1.0 A g −1 (about 3C), approximately 88.3% of the initial discharge capacity. It is believed that the unique nanoflake morphology of LiV 3 O 8 and the surface modification by graphene nanosheets contribute to the improved kinetics of lithium-ion diffusion, excellent structural stability and superior electrochemical performance. The structural evolution of LiV 3 O 8 species upon charging and discharging is investigated by in situ X-ray diffraction technique. Anisotropic lattice expansion is found occurring along a , b and c axes upon the insertion of lithium ions into the crystal structure of LiV 3 O 8 .