Graphene-coffee waste derived carbon composites as electrodes for optimized lithium ion capacitors

Herein we report an easy, ecofriendly and cheap synthetic approach for the preparation of carbon composites from the pyrolysis and activation of coffee waste and graphene oxide, and their evaluation as potential electrodes for lithium ion capacitors (LICs). An exhaustive optimization of some important parameters such as particle size, electronic conductivity or mass loading has been done for the battery-type electrode; whereas the optimum combination of specific surface area and pore size distribution were also investigated for the capacitor-type electrode. Optimized electrodes allowed to go one step beyond the state-of-the-art of biowaste based dual carbon LICs in terms of energy, power and cyclability. Assembled LICs show values of 100 Wh kg(AM)(-1) at 9000 W kg(AM)(-1) and retain above 80% of the initial capacitance after 3000 cycles, which is enhanced to 15,000 cycles by decreasing the voltage window. (c) 2020 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).