Lots of single-use water bottles made from poly(ethylene terephthalate) (PET) end up in landfills, but there’s a growing interest in upcycling them instead. Researchers in Energy & Fuels report on new heat-based fabrication methods to transform PET into supercapacitor electrodes and separator films for upcycled energy storage devices. In demonstrations, an all-plastic supercapacitor made from discarded water bottles outperformed a similar design that used a traditional glass fiber separator.