In an embodiment, a secondary Zn--MnO.sub.2 battery comprises a battery housing, a MnO.sub.2 cathode, a Zn anode, and an electrolyte solution. The MnO.sub.2 cathode, the Zn anode, and the electrolyte solution are disposed within the battery housing, and the MnO.sub.2 cathode comprises a MnO.sub.2 cathode mixture and a current collector. The MnO.sub.2 cathode mixture is in electrical contact with at least a portion of an outer surface of the current collector, and the MnO.sub.2 cathode has a porosity of from about 5 vol. % to about 90 vol. %, based on the total volume of the MnO.sub.2 cathode mixture of the MnO.sub.2 cathode.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
 The invention described and claimed herein was made in part utilizing funds supplied by the U.S. Department of Energy under Contract No. DE-AR0000150. The Government has certain rights in this invention.