The present invention demonstrates Br2-based conversion chemistry is a potential route toward rechargeable Mg-batteries. Compared with Mg-ion or Mg-air chemistries, the Mg—Br2 system features fast kinetics and good cyclability. In one embodiment, the present invention provides a rechargeable non-aqueous, dual-electrolyte scheme. In one embodiment, the anolyte consisted of Mg(TFSI)2 dissolved in a monoglyme and diglyme mixture, whereas the catholyte was composed of Mg(TFSI)2 in PYR14TFSI ionic liquid mixed with active bromine species. When Mg was used as the anode, an open circuit voltage of 3.0 V (vs. Mg2+/Mg) was measured.