Trash to treasure: Fallen leaves as separators for supercapacitors

Electrochemical double-layer capacitors are an essential type of energy-storage devices due to their fast charge/discharge rate, ultralong cycle life, and safe operation. A separator plays an important role in supercapacitors to prevent short circuit while allow ions to move through its porous structure. Herein, we demonstrated fallen leaves as efficient separators in supercapacitors with dense mesoporous carbon electrodes, achieving a high areal capacitance of 1.94 F/cm2. Among four leaves, Quercus rubra leaf exhibited the best electrochemical performance as a separator for supercapacitors, which is even comparable to the commercial glass fiber separator. This finding provides an approach not only to transfer waste into treasure but also to develop sustainable separators for energy-storage devices.