Graphene as Vehicle for Ultrafast Lithium Ion Capacitor Development Based on Recycled Olive Pit Derived Carbons

Abstract

Herein we report a series of lithium ion capacitors (LICs) with extraordinary energy-to-power ratios based on olive pit recycled carbons and supported on graphene as a conducting matrix. LICs typically present limited energy densities at high power densities due to the sluggish kinetics of the battery-type electrode. To circumvent this limitation, the hard carbon (HC) was embedded in a reduced graphene oxide (rGO) matrix. The addition of rGO into the negative electrode not only forms a 3D interpenetrating carbon network but also wraps HC particles, facilitating ion diffusion and enhancing the electronic conductivity notably at high power densities. Electrochemical impedance spectroscopy (EIS) analysis reveals that charge-transfer resistance at electrode-electrolyte interphase and the charge-transport resistance within the electrode are considerably lower in the presence of rGO. In addition, charge-transport resistance remains constant upon cycling even at increasing current densities. Capacity gain at high current densities, owing to the reduction of the electrode resistance, triggers the overall LIC performance, allowing for the assembly of an ultrafast LIC delivering up to 200 Wh kg(AM)(-1) at low power rates and 100 Wh kg(AM)(-1). (C) The Author(s) 2019. Published by ECS.