On-chip micro-supercapacitors for operation in a wide temperature range

•Micro-supercapacitor fabrication using ionic liquid mixture as electrolyte•Micro-supercapacitor with large voltage window (3.7 V at room temperature)•Micro-supercapacitor with large operation temperature (− 50 °C to + 80 °C)

Onion-like carbon (OLC) based micro-supercapacitor electrodes prepared by electrophoretic deposition (EPD) were combined with a eutectic mixture of ionic liquids (IL), producing a micro-supercapacitor which is able to function from − 50 °C to 80 °C. This device was electrochemically characterized by cyclic voltammetry and electrochemical impedance spectroscopy at different scan rates and different temperatures. At 20 °C, a capacitance of 1.1 mF.cm− 2 per footprint area of device at 200 mV.s− 1 within 3.7 V was measured, hence a specific energy of 15 mJ.cm− 2 and a specific power of 240 mW.cm− 2. At − 50 °C, 76% of the capacitance was maintained at 10 mV.s− 1 within 3.7 V. By integrating with IL, this micro-supercapacitor can be potentially used in portable electronic devices that are required to work under temperature extremes.