Powders, electrodes, zinc-air batteries and corresponding methods are provided. Powders comprise perforated shells having a size of at least 100 nm and comprising openings smaller than 10 nm. The shells are electrically conductive and/or comprise an electrically conductive coating. Powders further comprise zinc and/or zinc oxide which resides at least partially within the shells. Methods comprise wetting the shells with a zinc solution to yield at least partial penetration of the zinc solution through the openings, and coating zinc internally in the shells by application of electric current to the shells. Upon electrode preparation from the powder, cell construction and cell operation, zinc is oxidized to provide energy and the shells retain formed Zn O therewith, providing sufficient volume for the associated expansion and maintaining thereby the mechanical stability and structure of the electrode—to enable many operation cycles of the rechargeable zinc-air batteries.