The growth of electrical transportation is crucially important to mitigate rising climate change concerns regarding materials supply.Supercapacitors are high-power devices,particularly suitable for public transportation since they can easily store breaking energy due to their high-rate charging ability.Additionally,they can function with two carbon electrodes,which is an advantage due to the abundance of carbon in biomass and other waste materials (i.e.,plastic waste).Newly developed supercapacitive nanocarbons display extremely narrow micropores (＜0.8 nm),as it increases drastically the capacitance in aqueous electrolytes.Here,we present a strategy to produce low-cost flexible microporous electrodes with extremely high power density (＞100 kW kg-1),using fourty times less activating agent than traditionnal chemically activated carbons.We also demonstrate that the affinity between the carbon and the electrolyte is of paramount importance to maintain rapid ionic diffusion in narrow micropores.Finally,this facile synthesis method shows that low-cost and bio-based free-standing electrode materials with reliable supercapacitive performances can be used in electrochemistry.