Optical materials with colour-changing abilities have been explored for display devices 1 , smart windows 2 , 3 , or modulation of visual appearance 4 – 6 . The efficiency of these materials, however, has strong wavelength dependence, which limits their functionality to a specific spectral range. Here, we report graphene-based electro-optical devices with unprecedented optical tunability covering the entire electromagnetic spectrum from the visible to microwave. We achieve this non-volatile and reversible tunability by electro-intercalation of lithium into graphene layers in an optically accessible device structure. This unique colour-changing capability, together with area-selective intercalation, inspires fabrication of new multispectral devices, including display devices and electro-optical camouflage coating. We anticipate that these results provide realistic approaches for programmable smart optical surfaces with a potential utility in many scientific and engineering fields such as active plasmonics and adaptive thermal management.

Inspired by the design of composite materials, a novel composite supercapacitor is proposed, designed and tested, comprising an integrated cell with high power-and high energy-related electrode materials. The application-specific composite supercapacitors offered a weight reduction of 40-60% compared to same performance supercapacitors based on the high power or on the high energy-related electrode material only. ABSTRACTInspired by the design of composite materials, a novel composite supercapacitor is proposed comprising an integrated cell with high power-and high energy-related electrode materials so that the composite electrochemical double layer capacitor (EDLC) is the equivalent circuit of a high power EDLC of power P1 and energy E1 and a high energy EDLC of power P2 and energy E2 connected in parallel. A methodology is proposed and validated in this study for the design of an application-specific composite supercapacitor of power P and energy E, where P1/E1 > P/E > P2/E2.The methodology was tested successfully in application-specific composite supercapacitors of medium and large size, fabricated in this study in the form of pouch cell with organic electrolyte.The application-specific composite supercapacitors offered a weight reduction of 40-60% compared to same performance supercapacitors based on the high power or on the high energy-related electrode material only.Keywords: activated carbon; electrochemistry; energy storage; power source; supercapacitor. HIGHLIGHTS A novel composite supercapacitor is proposed inspired by composite materials. It comprises a cell integrating high power and high energy electrodes in parallel. A precise methodology is proposed for the design of a composite supercapacitor. The design of application-specific composite supercapacitors was tested successfully. Application-specific composite supercapacitors offered a 40-60% weight reduction.

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