Internally-externally molecules-scissored ramie carbon for high performance electric double layer supercapacitors

•Ramie porous carbon (in-ex-RPC) was prepared by internally-externally molecules-scissored activation strategy from waste ramie straw.•This in-ex-RPC with high specific surface area and high pore volume displays a specific capacitance of up to 300 f g–1.•The aqueous 6 M KOH based symmetric supercapacitors deliver a cyclic capacity of 90.9%-retaining after 20,000 cycles at 5 a g–1. And the EMIMBF4 based symmetric supercapacitors supply a high energy density of 65.5 Wh kg–1 at a high power density of 1.76 kW kg–1.•This strategy could contribute to energy storage applications of waste ramie straw and further promote clean utilization of waste biomass.