Nanostructured bismuth materials can be utilized as an insertion material in electrodes for magnesium energy storage devices to take advantage of short diffusion lengths for Mg.sup.2+. The result can be a significantly increased charge/discharge rates and/or improved cycling stabilities. In one example, an energy storage device has magnesium as an electroactive species, an electrolyte salt containing magnesium, and an anode having bismuth nanostructures. The bismuth nanostructures have at least one dimension that is less than or equal to 25 nm. At least a portion of the magnesium is reversibly inserted into, and extracted from, the anode during discharging and charging states, respectively.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
 This invention was made with Government support under Contract DE-AC0576RLO1830 awarded by the U.S. Department of Energy. The Government has certain rights in the invention.