Supercapacitors can be thought of as rapid-charging batteries. It can take just seconds to fully charger a supercapacitor whereas a conventional battery will take hours and sometimes a whole day to charge. But, the current supercapacitors lack something most rechargeable batteries have - capacity. They can be charged rapidly but they don't last long in use. Moreover, each discharge-charge cycle leads to degradation that means supercapacitors have much shorter lives than conventional batteries. Now, a team at Queen Mary University of London and the University of Cambridge, UK, have exploited a property of some polymer and composite supercapacitors known as pseudocapacitance. This property allows more charge to be packed in and side-steps the premature degradation. The UK team has developed an interpenetrated double polymer layer that allows them to rapidly charge and boost capacity to much greater levels than previous carbon-based supercapacitors.