Polypyrrole and cellulose extracted from algae are the key ingredients needed to make a greener battery. Those materials are flexible enough to be rolled together to make a compact energy storage device, and they can be easily recycled, according to Leif Nyholm, Maria Strømme, Albert Mihranyan, and their team at the University of Uppsala, in Sweden, who developed the idea (Nano Lett., DOI: 10.1021/nl901852h). Chemists have been trying to make heavy-metal-free, all-polymer batteries from organic conducting polymers, but none of the prototypes can be quickly or repeatedly charged. In search of a solution, the Swedish team turned to cellulose produced by Cladophora algae: It can be converted into cheap paper that is highly porous and resistant to moisture. By coating sheets of the paper with a 50-nm layer of either oxidized (doped) or reduced (undoped) polypyrrole to serve as electrodes, separating the two electrodes with an insulating filter paper, and immersing the fabricated cell in saltwater, the researchers built an all-polymer battery that can be charged to 600 milliamps per cm2 and recharged more than 100 times.