A battery includes a cathode having an oxide containing one or more metals and pentavalent bismuth, an anode, a separator between the cathode and the anode, and an alkaline electrolyte. The metal(s) can be an alkali metal, an alkaline earth metal, a transition metal, and/or a main group metal. The separator can be ion-selective or capable of substantially preventing soluble bismuth ionic species from diffusing from the cathode to the anode.