A novel electrolyte system for a rechargeable magnesium battery has been developed. The electrolyte consists of ethylmagnesiumbromide in tetrahydrofuran (EtMgBr/THF) with an ionic liquid (IL) of quaternary ammonium salt. The ionic conductivity of the electrolyte with the composition of EtMgBr/THF:IL being 3:1 in volume was 7.44 mS cm(-1) at 25 degrees C. A reversible processes of cathodic deposition and anodic dissolution of magnesium has been successfully achieved in the mixed electrolyte system of EtMgBr/THF + IL at room temperature. (C) 2009 Elsevier B.V. All rights reserved.