A method of generating an electrical current and a multi-cell electrochemical device. The method includes extracting oxygen from an aqueous ambient environment surrounding an electrochemical system; transporting the extracted oxygen through a selectively oxygen-permeable membrane to an enclosed electrolyte configured to surround an anode and a cathode in the electrochemical system, wherein the electrolyte is separated from the aqueous ambient environment; transporting the oxygenated electrolyte to the cathode; reducing the oxygen at the cathode; and oxidizing a metal at the anode. The device includes a metal anode; a cathode; an enclosed electrolyte configured to surround the cathode and the anode, wherein the electrolyte is separated from an aqueous ambient environment surrounding the electrochemical device; and a selectively oxygen-permeable membrane configured to extract oxygen from the aqueous ambient environment.