Disclosed is an electrolyte solution for a magnesium rechargeable battery with a high ionic conductivity and a wide electrochemical window compared to the conventional electrolyte solution. The electrolyte solution is prepared by dissolving magnesium metal into the ethereal solution using combinations of metal chloride catalysts. The electrolyte solution can be applied to fabricate magnesium rechargeable batteries and magnesium hybrid batteries with a markedly increased reversible capacity, rate capability, and cycle life compared to those batteries employing the conventional electrolyte solution. Also disclosed is a method for preparing the electrolyte.