A battery system includes a metal oxygen battery. The metal oxygen battery includes a first electrode and a second electrode. The second electrode includes a metal material (M). The metal oxygen battery is in communication with an oxygen storage material. In certain instances, the oxygen storage material is contained within an oxygen containment unit. The metal oxygen battery and the oxygen containment unit may be in a closed-loop with respect to each other. The battery system further includes a conduit for providing fluid communication from one of the metal oxygen battery and the oxygen containment unit to the other of the metal oxygen battery and the oxygen containment unit.