The V2O5 nano-crystal with an average diameter of 200 nm is prepared by a ball-milling with toluene and a calcination in air. Electrochemical properties of V2O5 nano-crystal for Li battery show that Li intercalation to V2O5 nano-crystal occurs reversibly and that the best condition of calcination temperature is 400°C. In the electrochemical test for Mg battery, Mg[TFSA]2/G3 electrolyte gives high discharge/charge capacities; 224/215 mAh g-1 at 3rd cycle, 180/177 mAh g"1 at 10th cycle, and 111/117 mAh g"1 at 30th cycle. An intercalation/dissociation of Mg2+ to/from layers of V2O5 nano-crystal is presumably controlled under a de-coordination/coordination of solvents from/to Mg2+. The intercalation of Mg2+ and a reduction of V2O5 are identified by XPS and XRD analyses. Extension of an interlayer distance from 5.75 À to 6.15 is observed by the intercalation of Mg2+.