An energy storage device can include a cathode having a first plurality of frustules, where the first plurality of frustules can include nanostructures having an oxide of manganese. The energy storage device can include an anode comprising a second plurality of frustules, where the second plurality of frustules can include nanostructures having zinc oxide. A frustule can have a plurality of nanostructures on at least one surface, where the plurality of nanostructures can include an oxide of manganese. A frustule can have a plurality of nanostructures on at least one surface, where the plurality of nanostructures can include zinc oxide. An electrode for an energy storage device includes a plurality of frustules, where each of the plurality of frustules can have a plurality of nanostructures formed on at least one surface.